Technical Report No. 213 036040-7- rI UNDERWATER SOUND PROPAGATION IN THE STRAITS OF FLORIDA: THE PRELIMINARY ANALYSIS OF THE MIMI EXPERIMENT OF 1970 by R. M. Heitmeyer Approved by' Theodore-G. Birdsall COOLEY ELECTRONICS LABORATO'RY Department of Electri.dal and Cbmputeir Engineering The University of'Michigan Ann Arbor, Michigan for Contract No. N00014-67-A-0181-0032 Office of Naval Research Department of the Navy Arlington, Va. 22217 February 1972 Approved for public release; distribution unlimited.

ABSTRACT An underwater acoustic propagation experiment was conducted (during the month of November 1970) as part of the Project MIMI propagation and signal processing research program. A periodic broadband signal modulating a 420 Hz carrier was transmitted continuously across the Straits of Florida for 19 days. At the receiving site, the power and phase angle of the carrier, the power in the signal sidebands and the noise power in the signal band were measured. In addition, the total power and the power spectrum in a narrow band about the carrier line were determined as a measure of the modulation due to the forward scattered surface reverberation. Finally, the correlation of the received signal with a stored reference was computed to measure the multipath structure and its stability. This report presents a brief description of the acoustical range, the experiment and the preliminary analysis of the data. iii

ACKNOWLEDGEMENTS The experiment described in this report was conducted as part of project MIMI propagation and signal processing research sponsored by Code 468 of the Office of Naval Research. The experiment was jointly conducted by the Acoustics Group of the Rosenstiel School of Marine and Atmospheric Sciences (RSMAS), University of Miami under the direction of Dr. John Steinberg, and by the Signal Processing Group of Cooley Electronics Laboratory (CEL), University of Michigan, under the direction of Dr. Theodore Birdsall. The Acoustics Group at RSMAS as a whole deserves special credit for not only maintaining the Miami-Bimini range but also for providing invaluable background information of the propagation conditions in the Straits of Florida. Special thanks go to Mr. Roger Dann who did an excellent job of both collecting the 7-mile hydrophone data and maintaining the equipment at RSMAS. The signal processing techniques used in the experiment were developed by Dr. Birdsall while the bulk of the credit for the computer implementation of those techniques goes to Mr. Kurt Metzger of CEL. Mr. Gerald Cederquist, Mr. Peter Wood and Mr. Brian Barton also made major contributions to the signal processing effort. iv

TABLE OF CONTENTS Page ABSTRACT iii ACKNOWLEDGEMENTS iv LIST OF ILLUSTRATIONS vi 1. The Mimi Experiment of November 1970 1 1. 1 The Miami-Bimini Range 2 1. 2 The Transmitted Signal 4 1.3 The Quantities Measured 10 1. 3. 1 Power and Angle Measurements 10 1. 3. 2 Surface Reverberation Measurements 12 1. 3. 3 Multipath Structure Measurements 13 1. 4 The Equipment Configuration 14 2. The Preliminary Analysis of the Data 20 2. 1 The Power Measurements 20 2. 1. 1 The Mean Powers 21 2. 1. 2 The Carrier Power and the Sideband 28 Power Measurements 2. 1.3 The Noise Power Measurements 33 2. 1. 4 The Reverb Power Measurements 37 2. 1. 5 The Standard Deviations About the 41 Mean Powers 2. 2 The Surface Reverberation Spectra 47 2. 3 The Multipath Structure Displays 55 2. 4 Environmental Measurements 66 2. 5 Summary of the Preliminary Analysis 67 APPENDIX A 74 APPENDIX B 107 APPENDIX C 140 APPENDIX D 173 DISTRIBUTION LIST 206 v

LIST OF ILLUSTRATIONS Figure Title Page 1 The Miami-Bimini range: (a) The Straits of 3 Florida, (b) bottom profile 2 Sound speed vs depth, Miami to Cat Cay, 28-29 5 November 1961 3 Sound ray paths along 25~ 44' on 28-29 Novem- 6 ber 1961 4 A complement-phase modulated signal 7 (a) a portion of the modulating waveform (b) the resulting transmission 5 The RMS spectrum of a complement-phase 9 modulated signal for L = 15 and D = 8 6 The frequency responses of the digital proces- 11 sing filter 7 A multipath display for two transmission paths 15 8 Equipment configuration at RSMAS (Miami) 16 9 Equipment configuration at Bimini 17 10 Block diagram of the digital processing imple- 19 mentation 11 Mean powers: Fowey Rocks to Bimini 22 12 Mean powers: Fowey Rocks to 7-mile 26 13 Carrier and sideband powers: Fowey Rocks 29 to Bimini 14 Carrier and sideband powers: Fowey Rocks 30 to Bimini vi

LIST OF ILLUSTRATIONS (Cont.) Figure Title Page 15 Carrier and sideband powers: Fowey Rocks 32 to 7-mile 16 Noise power: Fowey Rocks to Bimini 34 17 Noise power: Fowey Rocks to 7-mile 38 18 Reverb and noise powers: Fowey Rocks to 39 7-mile 19 Reverb, sideband and noise powers: Fowey 40 Rocks to Bimini 20 Standard deviations: Fowey Rocks to Bimini 42 21 Standard deviations: Fowey Rocks to 7-mile 45 22 Reverb spectra displays: Fowey Rocks to 48 Bimini 23 Reverb spectra displays: Fowey Rocks to 49 7-mile 24 Reverb spectra displays: Fowey Rocks to 50 Bimini 25 Reverb spectra displays: Fowey Rocks to 54 Bimini 26 Reverb spectra displays: Fowey Rocks to 56 7- mile 27 Multipath structure displays: Fowey Rocks 59 to Bimini 28 Multipath structure displays: Fowey Rocks 61 to Bimini 29 Multipath structure displays: Fowey Rocks 64 to 7-mile vii

LIST OF ILLUSTRATIONS (Cont.) Figure Title Page 30 Water temperatures at Bimini 68 31 Tide level at Bimini 69 32 The times of the main events at Bimini 70 viii

Chapter 1 THE MIMI EXPERIMENT OF NOVEMBER 1970 The underwater acoustic propagation experiment of November 1970 was conducted jointly by the Acoustics Group of the Rosenstiel School of Marine and Atmospheric Sciences at the University of Miami and by the Signal Processing Group of the Cooley Electronics Laboratory at The University of Michigan. A periodic, broadband signal, modulating a 420 Hz carrier was transmitted continuously across the Straits of Florida for 19 days. At the receiving site, the power and phase angle of the carrier, the power in the signal sidebands,and the noise power in the signal band were measured. In addition, the total power and the power spectrum in a narrow band about the carrier frequency were determined as a measure of the modulation due to the forward-scattered surface reverberation. Finally, the correlation of the received signal with a stored reference was computed to measure the multipath structure of the channel and its stability. During the course of the experiment approximately 9 million digital words of the reception were recorded for later processing. This report, however, contains only the description of the experiment and the preliminary analysis of the on-line results. A more complete report on the results of additional processing of the data is planned.

2 1. 1 The Miami-Bimini Range Location and Facilities. The Miami-Bimini range, illustrated in Fig. 1, is part of the facilities of the Acoustics Group of the Rosenstiel School of Marine and Atmospheric Sciences (RSMAS) of The University of Miami. 1It extends across the Straits of Florida from Miami to Bimini, Bahamas. The transmitting site is located at Fowey Rocks [ point 2, Fig. l(a)] approximately 12 miles from the RSMAS laboratory. At the transmitting site, which is connected to the RSMAS laboratory by telephone lines (point 1, Fig. 1), a bottom mounted projector is located in 72 feet of water at the focal point of a 24 ft. compliant tube, parabolic reflector. It has a maximum output level of 120 dB/ lbar at one meter with a nominal bandwidth of 100 Hz. The 30~ beamwidth is directed toward Bimini, a distance of 43 nautical miles Two receiving sites were used in the experiment. At the first of these, a bottom mounted hydrophone is located in 1000 feet of water at point 4 in Fig. l(a) approximately 7 miles from the source. The reception from this hydrophone was transmitted to the RSMAS laboratory by marine cable. This site is hereafter referred to as the 7-mile hydrophone. The second receiving site is located off Bimini at point 3 (Fig. 1). There, two bottom mounted hydrophones J. C. Steinberg, and T. G. Birdsall, "Underwater Sound Propagation in the Straits of Florida," J. Acoust. Soc. Am., 39, 301-315 (1966).

25' -. Depth in fathoms. "0' o''B 1 13 2d50-; -*;. |/r-^116 170 MIAMI' ~ i 2 MIA MARINE LAB 4 \.A N BIM1 0 5 U S 721< (h I,. FO EY ROCKS 5 1 r' <.: CAT CAY 230' ___723. 23/ 4 N 24 M9 406 197 1214,~ j~~~~~~~~~~~~~1 20' f 75. 3" ~ 490 447.0:'P~~~ /I T' i 360 " / (O N To- --- -- -- — ~ - - --- *- - --- --- LC O CAE LON 200 ~ 400 ^ Y / \ 600 800 (VERTICAL SCALE 37 K HORIZONTAL) 0 10 20 30 40 N. MILES (ONE —ONES —-CAE. - (ONE TO ONE SCALE) Fig. 1. The Miami-Bimini range: (a) The Straits of Florida, (b) bottom profile

4 are cable-connected to a laboratory on Bimini. These hydrophones are located at 100 and 1200 feet, 1 and 2 miles off shore and are referred to as the shallow and deep hydrophones, respectively. Oceanographic and Acoustical Characteristics. The bottom profile of the Miami-Bimini range is illustrated in Fig. l(b). A shelf extends out from Miami about 15 miles to a depth of 400 meters followed by a sharp drop-off to a depth of 800 meters. Thirty miles beyond, the Grand Bahamas bank rises abruptly from this depth. A velocity profile, obtained during November 1961, appears in Fig. 2. This profile is characterized by a mixed layer which extends to the relatively constant depth of 100 meters followed by a region of negative velocity gradient. It is noted that the velocity gradient becomes increasingly negative as the Florida shore is approached. The ray diagram corresponding to the velocity profile of Fig. 2 is shown in Fig. 3. This diagram shows sound being propagated by reflections from surface and bottom, by refraction and reflection from the bottom and by refraction and reflection from the surface. This latter mode of propagation does not appear in ray diagrams calculated from velocity profiles obtained in the spring and summer. 1. 2 The Transmitted Signal The transmitted signal consisted of a linear-maximal, pseudorandoml sequence used to complemenlt-lphase modulate (CPM) a calrrier.

5 NAUTICAL MILES 0 10 20 30 40 WEST LONG. 00 7 50' T' 7' 792 I.^6 i o i// /' r-` —...2- s -2 71 4 / /? 72 / 0 -- ~Q(I~~,,,,,, _, _ "200 a 1540 MAG. 15_ 1 520 1540 SOUND SPEED SCAWE - WSEC 0/., 0 00 f = carrier c d = duration of the sequence dig it D = number of cycles of carrier per sequence A-~.... -. -600 d = duration of the sequence digit

t96r. 4 ~ ~ ~0/6'IOnr.CCOS.& _ 1 / I: Zc:

'7 +1 =D/~f -1 (a) - Ij -/fc (b) Fig. 4. A complement-phase modulated signal (a) a portion of the modulating waveform (b) the resulting transmission Evidently d = D/fc Furthermore, when the number of cycles of carrier per digit D is integer-valued, the signal is periodic with period T =Ld = LD/f where L is the number of digits in one period of the modulating sequence.

8 The RMS power spectrum of a typical (CPM) signal is shown in Fig. 5 for the special case L = 15 and D = 8. It is seen that this spectrum has a sin(x)/x envelope except at the carrier frequency. It can easily be shown that approximately half of the total power is contained at the carrier frequency with the other half contained in the sideband frequencies. For the specific signal used in the experiment, f = 420 Hz c D = 8 cycles/digit and L = 63 digits with the result that the digit duration and the period were d = 0. 019 seconds and T = 1.2 seconds Furthermore, the frequency line spacing Af and the effective signal band B (frequency spread between the spectral zeros on either side of the carrier) were Af = 1/T = 0.8333 Hz B = 2/d = 105 Hz Finally, it can be shown that there are 125 spectral lines lying within the signal band.

9 -~1 ~~~~~1 [S (f)]2 f d d Fig. 5. The RMS spectrum of a complement-phase modulated signal for L = 15 and D = 8

10 1. 3 The Quantities Measured The quantities measured in the November 1970 experiment can be grouped into three categories: (1) signal power, noise power and carrier angle measurements, (2) forward-scattered surface reverberation measurements, and (3) multipath structure measurements. These measurements are obtained using digital processing techniques implemented by a digital computer located at each receiving site. (See Section 1. 4.) Each of the measurements is computed and recorded every 100 seconds on the basis of 80 seconds of data. (The remaining 20 seconds are used solely for computations.) The specific quantities measured are described in the following paragraphs. 1. 3. 1 Power and Angle Measurements. C Power. The C power measurement is a measure of the power present in the carrier of the received signal. It is determined as that power passing through a digital processing filter with a frequency 3 response, Hc(f), as illustrated in Fig. 6(a). Note that due to the narrow bandwidth, 3(0. 013 Hz), Hc(f) passes only the carrier frequency and none of the sideband frequencies present in the spectrum of the transmitted signal. 2Only the main lobes of the frequency responses of the processing filters in Fig. 6 are illustrated since these lobes contain almost all of the total power. By bandwidth we mean 1/2 the frequency spread between the two zeros on either side of the center frequency of the main lobe.

Hc(f) A-.013 Hz C~~~~~~~~~ f= 420 Hz f C (a) fig(f) -1.013 IIz -*1 af -.833 Hz -- fAf f + Af f C (b) + ff (f I( ~.013 Hz -j H f =.833 Hz 1 f af _, Af f f- -T (C) c + T H (f) ~ -.833 Hz f (d) Fig. 6. The frequency responses of the digital processing filter

12 N Power. The N power measurement is a measure of the noise power contained within the signal band: f - B/2 < IlI < f + B/2. C -C It is determined as that power passing through the digital processing filter with a frequency response, HN(f), as illustrated in Fig. 6(c). Such a filter is often referred to as a comb filter. Note that each "tooth" in HN(f) is centered midway between the spectral lines in the signal spectrum, and the bandwidth of each tooth is again 0. 013 Hz. S Power. The S power measurement is a measure of the signal power within the signal band, excluding the carrier power. It is determined as that power passing through the digital processing filter with frequency response HS(f) as illustrated in Fig. 6(b). This filter is recognized as a comb filter with a tooth missing at the carrier frequency. The remaining teeth are aligned with the line frequencies of the transmitted signal. The bandwidth of each tooth is 0.013 Hz. Carrier Angle (A). The carrier angle is a measure of the relative difference between the phase of the output of the carrier processing filter and the phase of the local reference oscillator (see Section 1. 4). 1.3. 2 Surface Reverberation Measurements. The effect of surface reverberation is to scatter some of the power of a transmitted 4 The filter H,,(f) is used to calculate the noise power only at the Bimini receiving site. An equivalent, but different, technique is used for the 7-mile data.

13 frequency into sidebands on either side of that frequency. It is felt that this scattered power should lie between 0. 1 Hz and 0. 4 Hz on either side of the transmitted frequency, depending on the spectrum of the surface waves. For the signal used in the experiment, the spacing between the lines in the power spectrum is Af = 0. 8333 Hz so that the sideband line frequencies do not interfere with the power scattered from the carrier frequency. Thus, the effect of surface reverberation can be measured by computing the power spectrum at the output of the processing filter whose frequency spectrum, HR(f), is shown in Fig. 6(d). Note that the bandwidth of HR(f) is large enough to include the power scattered by surface reverberation but small enough to exclude the power in the signal sidebands. In addition to computing the reverberation or "reverb" spectra, the total power at the output of HR(f) minus the carrier power is also computed. This power, referred to as the reverb power or R power, is a measure of the power in the sidebands of the reverb spectrum. 1. 3. 3 Multipath Structure Measurements. The magnitude of the cross-correlation function between the demodulated reception and a pulse-compression reference is computed to measure the multipath structure of the channel. In the absense of noise, this function has a triangular peak of width, 2d = 0. 038 seconds, centered at the arrival time of each transmission path mod(T), and an amplitude proportional

14 to the amplitude of the signal received over that path. For example, the cross-correlation function for the special case of only two transmission paths is shown in Fig. 7. Note that this is the same function as would be obtained if a single, large, one-digit pulse were transmitted once every T seconds and received through a matched filter. As a measure of the time stability of the channel multipath structure, the zero-delay complex cross-correlation coefficient between the demodulated received signal and a previously stored replica of the received signal is calculated for each data set. When this coefficient falls below a set value, indicating a marked change in the multipath structure, the current signal becomes the replica, and the new multipath picture is displayed. Otherwise, the previous replica is displayed and retained in storage. The changing magnitude of the correlation coefficient is an indicator of how fast the multipath structure is changing. 1. 4 The Equipment Configuration The configuration of the equipment used in the experiment is shown in Figs. 8 and 9. Figure 8 illustrates the configuration used in the generation and transmission of the signals and in the processing of the reception from the 7-mile phone at Miami. Figure 9 shows the configuration used in the processing of the reception at Bimini. The operation of the equipment in Fig. 8 is as follows. The frequency standard (accurate to 1 part in 10 ) provides a 100 KHz

15,1,___ Time I-2d -A 2d < —.. T seconds - l Fig. 7. A multipath display for two transmission paths reference signal which is converted to a 1680 Hz (= 4x carrier frequency) clock signal by the frequency synthesizer and then passed through an isolation amplifier. One output of the isolation amplifier is used as a reference for the digital modulator whose output, after filtering, is the CPM signal described in the preceding section. This signal is amplified and then transmitted down the Miami-Bimini range. The reception at the 7-mile hydrophone is amplified and transmitted back to the RSMAS laboratory. There it is filtered and amplified and then processed by the LINC-8 computer. The other output of the isolation amplifier provides a clock signal to the LINC-8 computer for use in sampling the reception. The receiving equipment at Bimini (Fig. 9) operates in essentially the same way as the receiving equipment at Miami. The receptions from both the deep and the shallow hydrophones are

Frequency Standard Frequency Synthesizer Isolation 1680Hz Amplifier clock''^ __i'7- mile PSMAS |\1___ Digital _____~~~~ L --. ^Transducer Hydophone Digital Bandpass L Rocks 7-mile Modulator i Filter A mpl ifier f Power channel Amplfier chnAmplifiere Telepone Lines d I |RSMAS Fowey Amplifietr Ban TdTe al minal Rocks -- Marine Cable Fi lter Amplifier Amplifier | —< —- Filtered reception Lin-8 Computer _ and Peripheal Equipment Fig. 8. Equipment configuration at RSMAS (Miami)

Deep Water Hydrophone Ap lf i \- - Terminal Bancidpass Isolation Controllable Amplifier Amplifier Filter Amplifier Attenuator Fle Marine filtered _ reception Cable PDP- 8 D -l ApfrTerminal Bandpass Isolation ormut.Amplif ier 10and Amplifier Filter Amplifier Periphea Shallow-water Equipment Hydrophone Frequency Frequency Standard Synthesizer 1680 Hz clock signal Fig. 9. Equipment configuration at Bimini

18 transmitted to the laboratory at Bimini and then amplified and filtered. The reception from one of the two hydrophones then enters an attenuator whose attenuation is controlled by the past signal level into the PDP-8 computer. The output of the controllable attenuator is first amplified and filtered and then processed by the computer. The coherent clock signal for the computer is obtained from a frequency standard and synthesizer identical to that employed at Miami. The digital computers appearing in Figs. 8 and 9 are used to implement the processing filters and to calculate the reverb spectra and multipath displays as discussed in Section 2. 3. In this capacity, these computers function as indicated in Fig. 10.

19 Filtered Reception 1680 Hz Clock Complex J_ Demod. --— H 3(f) - N Power S Power I -----— | HS(f) I I Correlator - Multipath Display 1l —----— HC M(f) C Power, C Angle _ R Power |I~ -I — "!HR(f) ISpectrum Reverb Spectrum Fnalyzer Fig. 10. Block diagram of the digital processing implementation

Chapter 2 THE PRELIMINARY ANALYSIS OF THE DATA Measurements of all of the quantities discussed in Section 1. 3 were made at Miami from the 7-mile hydrophone for 20 days. At Bimini approximately 8 days of measurements were taken from the deep-water hydrophone and 11 days of measurements were taken from the shallow-water hydrophone. This chapter presents the preliminary analysis of the data from 15 of the 20 days, excluding the carrier angle and the correlation-coefficient measurements which will be discussed in a later report. 2. 1 The Power Measurements The power measurements, expressed in decibels relative to an arbitrary reference, have been plotted as continuous functions of time. (Continuity has been obtained by linear interpolation between the discrete data points. ) Two different vertical scales have been used. In the one case, the vertical scaling is determined as if the gain of each of the processing filters in Fig. 6 is equal to unity. These plots are referred to as the unity-gain plots (UG). In the other case, the vertical scaling has been determined as if the product of the gain and the bandwidth of each of the processing filters were constant. These plots are referred to as the constant gain-bandwidth (CGB) plots. The CGB plots have the property that the approximate signal-to-noise ratio 20

21 (in dB) at the output of the processing filters HC(f), HS(f) and HR(f) can be obtained simply by subtracting N power from C, S or R power respectively. UG and CGB plots of the power measurement for the complete experiment are found in Appendices A through D. In this section the essential features of these plots are summarized. 2. 1. 1 The Mean Powers. The general character of each of the power measurements is best illustrated in terms of a slowly varying component and the amount of additional variation about this component. The slowly varying component or "mean power" has been estimated by computing a sliding average. The amount of variation about the mean power has been estimated by computing a sliding standard deviation. In the following paragraphs the mean powers, based on a three-hour averaging time, are discussed. For notational convenience, the mean powers are distinguished from the actual measured powers by using a subscript "m". For example, C dem notes the mean carrier power obtained by averaging the carrier power measurement C. The standard deviations about the means are discussed in Section 2. 1. 5. Figures 11(a) and ll(b) illustrate the mean powers from the Bimini data plotted on a CGB scale. The deep hydrophone mean powers appear in Fig. 11(a) for 14 November through the evening of 17 November. During this period, the mean sideband power is relatively

dB 160 160 DEEP WATER HYDROPHONE - SHALLOW WATER HYDROPHONE 140 120 S 100 R tyN 1 -X 80 60 40 20 2....;:__ __ _. _____. ~ _ &. ____ 14 15 16 17 18 19 20 21 (a) DATE: NOVEMBER 1970 Fig. 11. Mean powers: Fowey Rocks to Bimini

dB 160 140 40 120 100 (b) r., 80 60 40 20....__L_ _JL. I.!........._ I 22 23 24 25 26 27 28 29 DATE: NOVEMBER 1970 Fig. 11. (Cont.)

24 constant around 110 dB and the mean carrier power varies somewhat more around the value of 130 dB. There appears to be only a small correlation between C and S. The mean noise power reaches a m m low on 15 November, then abruptly rises 15 dB to a new value and remains at that new value with very little variation for the remainder of the deep-water data. In the period preceding the jump, N shows a significant amount of variation. The mean reverb power, Rm, with the exception of a short period on 15 November, exceeds N by less than 8 dB and both R and N appear to be highly correlated. The remaining Bimini data were taken from the shallow hydrophone. The mean powers constitute the rest of Fig. 11(a) and all of Fig. 11(b). For approximately half of the time, the sideband power is reasonably constant around 105 dB, but, during the remaining time, S varies considerably with local maxima from 10 5 to 20 dB higher than the nominal value. During the period of stable sideband power, C is also reasonably stable and there appears to be some correlation between the two. During the periods of high sideband power, however, Cm is also quite high and the two powers are highly correlated. The difference in the power levels between the deep hydrophone power measurements and the shallow hydrophone power measurements can be attributed to the gain settings of the amplifiers in the pre-processing equipment.

25 The shallow water mean noise power exhibits two different kinds of behavior. On the one hand, N suffers an abrupt 15 dB m gain and then does not return to its original value for a period of several days [see 22 November, Fig. 11(b)]. This is similar to the jump in the deep hydrophone noise power except there is more variation following the jump. In contrast to the "jump type" variations in the shallow-hydrophone noise power, there are several instances where N rises about 10 dB and then immediately returns to the original value. These "roll-type" variations seldom last longer than several hours. The behavior of the shallow-water reverb power during the periods of stable S is much like the behavior of the deep hydrophone reverb power. It maintains a fairly constant value except during the rolls in noise power. During the periods of high Sm however, the reverb power is also high and the three powers S, Cm and Rm all vary together. Figures 12(a) and 12(b) illustrate the mean powers for the 7-mile data. The most striking feature of these plots is the high degree of stability in all four powers in contrast to the instability of the corresponding powers from the Bimini data. It is noted that the mean sideband power varies less than 10 dB during the course of the experiment, and the range of variation in the mean carrier power is only slightly greater. It should also be noted that although C m

dB 160 140 C 120 S 100 80 60 40 20.. _ L. _/._... t 4 _ ~,,.,, 14 15 16 17 18 19 20 21 DATE: NOVEMBER 1970 Fig. 12. Mean powers: Fowey Rocks to 7-mile

dB 160 140 120 100 80 -- 60 40 20 1... - _. I. _ 22 23 24 25 26 27 28 29 DATE: NOVEMBER 1970 Fig. 12. (Cont. )

28 and S are only slightly correlated, the mean reverb power and the m mean noise power show a substantial correlation. In the above paragraphs we have discussed the plots of the four mean powers from each receiving site. These plots present the general characteristics of the power measurements for all 19 days of data in terms of two plots for each receiving site. In order to investigate the local behavior of the power measurements, however, it is necessary to examine specific examples of the CGB plots from the appendixes. This is done in the next three subsections. 2. 1. 2 The Carrier Power and the Sideband Power Measurements. Figures 13(a) and 13(b) illustrate two CGB plots of the carrier power and the sideband power taken from the stable S-power portion of the Bimini shallow hydrophone data. It is seen that C power varies over a wide range with most of the variation consisting of sharp, deep fades of up to 30 dB. The rate at which these fades occur varies from as little as one fade per two hours to as much as two fades per hour with an average fade rate of approximately one fade per hour. The amount of variation in the sideband power is small, with several periods during which S power varies less than 3 dB in 3 hours. Figures 14(a) and 14(b) illustrates two CGB plots of the carrier power and the sideband power taken from the high S-power portion of the Bimini data. In Fig. 14(a), S rises to 118 dB,

13u - C dB 120 110 100 19 Nov. I I l! I I I l I l I 1 2 3 4 5 6 7 8 9 10 11 12 i (a) TIME (HOURS) 130 dB 120 110 100 s 27 Nov. I I I I I I l i I I 13 14 15 16 17 18 19 20 21 22 23 24 (b) TIME (HOURS) Fig. 13. Carrier and sideband powers: Fowey Rocks to Bimini

140 dB 130 120 110 23 Nov. 140 dB 130 120 110 1 2 3 4 5 6 7 6 9 10 11 12 (b) TIME (HOURS) Fig. 14. Carrier and sideband powers: Fowey Rocks to Bimini

31 18 dB higher than its nominal value, and in Fig. 14(b) S rises to 124 dB. In both Figs. 14(a), (b), it is noted that the carrier power is well above its nominal value, that the C-power fade rate is considerably less than its nominal value, and that both C power and S power are highly correlated. The C- and S-power measurements taken from the 7-mile data have much the same general character as the C- and S-power measurements taken from the stable S portion of the Bimini data. The 7-mile C power also has fades as deep as 30 dB and the 7mile S power also has only a small amount of variation. There are, however, two significant differences between the 7-mile C and S powers and the Bimini C and S powers. First, the 7-mile C power fade rate, (on the average), is noticeably less than the Bimini C-power fade rate. Figures 15(a) and 15(b) illustrate two representative CGB plots of C and S power from the 7-mile data. It is seen that there are several periods of over three hours where at most one deep fade occurs. There are, of course, many periods from the 7-mile data with a high C-power fade rate [for example between 1500 hrs and 2000 hrs in Fig. 15(a)], but a cursory examination of all the data from both sites indicates that the 7-mile C-power fade rate is approximately half the Bimini C-power fade rate.

130 dB C 120 110 100' wiv /~-J<yr- js 1 ~~~~~~~~~~~~~~~~~~~~19 Nov. ---— i —— ^ —-^ —- ----— ~ —-^ —--- L____ 8 9>' 130 (a) 10 11 12 dB"Fg 15 p.. n TIME (HOURS) 120Carrer and Seband powers C 110 t lo r - I\ L 1 ~~~~~~~~~~27 Nov. (b) z- i - Fig.16.Carrier and sidebn r (ola powes: oweY Rocks to T-mile

33 The second major distinction between the 7-mile C and S powers and the Bimini C and S powers lies in the dependency of the C-power fade rate on the level of S power. In the 7-mile data, the C-power fade rate appears to be independent of the level of S power. In the Bimini data, however, the C-power fade rate is much lower during the periods of high S power than it is during the periods of stable S power. 2. 1.3 The Noise Power Measurements. The Bimini noise power measurement varies over a range of 30 dB during the course of the experiment. Part of this variation consists of changes between 10 and 15 dB in the mean N power due to "jumps" and "rolls" as discussed in Section 2. 1. 1. In addition, there are large isolated 20 to 30 dB spikes which can be attributed to local shipping noise. Finally, there is a small portion of the Bimini data during which 5 to 10 dB spikes occur at a rate of from three to five spikes an hour. To illustrate these different behaviors, four different 12 hour segments of the Bimini noise power are presented in Figs. 16(a) to 16(d). Figure 16(a) illustrates a jump of 18 dB in the noise power. Note that N power is considerably more stable after the jump than before the jump. Figure 16(b) shows the noise power over the same 12-hour period a day later. The N power measurement has remained

120 dB 110 N 100 90 15 Nov. 13 14 15 16 17 18 19 20 21 22 23 24 (a) TIME (HOURS) 120 110 dB 100 90 - 16 Nov. 13 14 15 16 17 18 19 20 21 22 23 24 (b) TIME (HOURS) Fig. 16. Noise power: Fowey Rocks to Bimini

120 dB 110 26 Nov. 100 N 90 1 2 3 4 5 6 7 8 9 10 11 12 (c) TIME (HOURS) n 120 dB 110 20 Nov. N 100 90 13 14 15 16 17 18 19 20 21 22 23 24 (d) TIME (HOURS) Fig. 16. (Cont.)

36 at the same level and there is still very little variation about this level. The two sharp peaks are examples of local shipping noise. Figure 16(c) illustrates that portion of the Bimini data during which the large, closely spaced spikes occur. It is unlikely that these spikes are due to local shipping noise in the light of their high repetition rate and the time of day when they occur. Figure 16(d) illustrates a roll variation in the noise power. At 1800 hours, the level of the noise power increases 15 dB and then returns to its original level, all within a period of three hours. These roll variations occur fairly often at different times in the shallow-water data. It is interesting to note, however, that on most of the days when shallow-hydrophone data were taken, a roll began between 1730 and 1800 hours and lasted from two to three hours. (See the figures for the first 12 hours for November 18 to 22, 25, 26, and 28 in Appendix A. ) It is reasonable to assume that these rolls can be attributed to biological activity. The 7-mile N power measurement differs from the Bimini N power measurement in two ways. First, as mentioned in Section 2. 1. 2, there are no appreciable jump or roll type variations in the 7-mile noise power. Second, the large, closely spaced, spiked variations that occur only once in the Bimini N power, occur six

37 times in the 7-mile N power with each occurrence lasting from 6 to 24 hours. In the remaining portion of 7-mile noise power data, there is only a small amount of variation with the exception of occasional shipping noise spikes. Figures 17 and 18 illustrate different 12-hour segments that are typical of the 7-mile noise power measurement. 2.1.4 The Reverb Power Measurements. The Bimini reverb power can be viewed as consisting of small amplitude variations about the mean R power of Fig. 11, Section 2. 1. 1. As mentioned in Section 2. 1. 1, R power varies according to N power during the periods of stable S power and varies according to S power during the period of high S power. Detailed examples of this dependency of R power on N power and on S power appear in Fig. 19(a) and (b) respectively. It should be noted that the level of R power in Fig. 19(b) is from 10 to 20 dB higher than the level of R power in Fig. 19(a). The 7-mile reverb power resembles the 7-mile noise power in behavior. The two mean powers vary together during the whole experiment as discussed in Section 2. 1. 1. Moreover, the 7-mile R power also has long periods during which large amplitude, closely spaced spikes occur and long periods when there is only a small amount of variation about the mean value. In fact, there is a high correlation between the amount of variation in R power and the amount

100 dB 90 80 N 7u 1 8 Nov. 1 2 a 4 5 6 7 8 9 10 11 12 10Oci dB~100b~ hTIME (HOURS) 0 dB 90 N 80 18 Nov. 70 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) Fig. 17. Noise power: Fowey Rocks to 7-mile

luo dBl 90 80 W /T MI (AORS tdeverb and fl>ise PO8ers: F'O~ ey I~ oeks t1 9 018 Reverb find TtA{E (B~m~s2 13 —^ -—..........t7 17 —-- 21 Fi. p.Ruevs: Fowey ROcks to 7-,i e ^ "'*kstotE (SO tms

90 80 19 Nov. 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) v 130 - dB 120 / S 110 100 25 Nov. N 1 2 3 4 5 6 7 TIME (HOURS) Fig. 19. Reverb, sideband and noise powers: Fowey Rocks to Bimini

41 of variation in N power. This is apparent in Fig. 18 which illustrates the two power measurements from 19 November. It is also noted from Fig. 18 that the R power signal-to-noise ratio is exceptionally high. We will return to this point in Section 2.2. 2. 1. 5 The Standard Deviations About the Mean Powers. In the above paragraphs, the power measurements have been described in terms of the slowly varying mean powers and specific examples of the CGB plots illustrating the character of the variations about the means. As a quantitative measure of this variation, sliding standard deviations for each power have been computed using a 25-minute averaging time. For notational convenience the standard deviation of each power is denoted by a "a" with a subscript denoting the power; for example, aN denotes the standard deviation of the N power measurement. The plot of the standard deviations for the Bimini powers is illustrated in Fig. 20. The fades in C power appear as sharp spikes in aC Thus, those periods during which the spikes in aC occur less frequently correspond to the periods of low C-power fade rates. The jump and roll type variations in N power do not appear in aN However, the period during which the large, closely spaced spikes occur, appears as a 3 dB increase in the level of aN [compare the morning of 25 November in Figs. 16(c) and 20(b)]. The shipping noise

dB..2.... DATE NOV. 4Fig 2 Standard deviations: Fowy R s to [ I Il.. I _ 14 15 16 17 18 19 20 21 DATE NOV. 1970 Fig. 20. Standard deviations: Fowey Rocks to Bimini

dB 6 I i j 6 I i 22 23 24 25 26 27 28 29 DATE NOV. 1970 a^~~N:~Fig. 20. (Cont ) 22 23 24 25 26 27 28 29 DATE NOV. 1970 Fig. 20. (Cont.)

44 in N power also appear as spikes in aN. It is noted that some of these also appear in aS and aR when S power and R power become noise-driven by the large shipping noise spikes. An important point to be noted in Fig. 20 is that, with the exception of the shipping noise spikes, aS is reasonably constant. This indicates that the amount of variation in the sideband power is essentially the same throughout the experiment. The same statement holds for both R and N power, if two 6-hour segments, one on 15 November and one on 23 November, are excluded from aR, and one 6-hour segment on 26 November is excluded from N. Figure 21 illustrates the standard deviations for the 7-mile power measurements. The lower 7-mile C-power fade rate is indicated by the smaller number of spikes in r C. Note also that the average level of the 7-mile aC is significantly less than the average level of the Bimini aC indicating less variation in the 7-mile C power. It is also seen that the spikes in aN due to shipping noise are smaller than those in the Bimini aN Also, none of these spikes appear in aS and only a few appear in R. This is a result of the higher signal-to-noise ratios at the 7-mile hydrophone. Special attention should be given to the behavior of cR and aN in Fig. 21. Both oR and aN have frequent periods during which they rise several dB. These increases in aR and aN are the result of large amounts of variation about the average levels. The high

dB OC 6 4 2 iii 0 C's 6 4 2 0 2 |M/wA^^^^. Y^ihihLhnvi~ aR 6 4 2 0 6 4 2 0 14 15 16 18 20 2 DATE NOV. 1970 Fig. 21. Standard deviations: Fowey Rocks to 7-mile

dB o 6 UIs 4 6 ON 6 N 2 i. 22 23 24 25 26 27 28 29 DATE NOV. 1970 Fig. 21. (Cont.)

47 correlation between these periods of increase in ao and aN is aplparlent. 2. 2 The Surface Reverberation Spectra In the preceding section the behavior of the reverb power at both receiving sites was discussed qualitatively. In this section, examples of the surface reverberation (reverb) spectra are presented and discussed. Recall from Section 1. 3 that the reverb spectrum is that portion of the received spectrum contained within a bandwidth of 0. 833 Hz centered about the carrier frequency. Thus, the reverb spectrum contains the power in the carrier frequency line, the power scattered from the carrier line by the surface reverberation, and that portion of the noise power normally lying within the reverb bandwidth. To illustrate the decomposition of the reverb spectrum into its components, displays from each receiving site are presented in Fig. 22. Thetickmarks on the frequency axis of each display are separated by 0. 1 Hz and the amplitude is expressed in dB with the two vertically spaced tick marks indicating a difference of 20 dB. Figure 24(a) shows the spectrum when only noise is present, and Fig. 24(b) shows the spectrum when both signal and noise are present, both displays are taken from the Bimini data. It is seen that when only noise is present, the carrier line appears as a dot above the center frequency and the reverb power appears in sidebands about the carrier line.

48 20dB I-0. I;,. I. 4H -0.4Hz 0 0.4Hz Fig. 22. Reverb spectra displays: Fowey Rocks to Bimini Figure 23(a) and (b) show two displays taken from the 7-mile data at two different times when no signal was transmitted. Notice that there is a 0. 2 Hz bandwidth over which the spectrum level is 20 dB higher than the level in the remaining portion of the reverb bandwidth. Note also that the center frequency of each excursion is different. It is doubtful that these excursions are characteristic of the ocean noise, and until a more complete investigation is made, they must be attributed to signal leakage somewhere in the 7-mile processing equipment. It might also be mentioned that the additional power present in the display of Figs. 23(a) and (b) would account for as much as 13 dB of the 7-mile R power measurement.

49 I -A i i I i., i I I. i, (a) (b) 2 dB ~T~G __ I I I I, -0.4Hz 0 0.4Hz (c) Fig. 23. Reverb spectra displays: Fowey Rocks to 7-mile Figure 23(c) illustrates a typical 7-mile reverb display when signal is also present. It is not possible to determine what percentage of the sidebands must be attributed to signal leakage in the equipment. We begin the description of the reverb displays with examples from the Bimini data. As might be expected, the most significant reverb sidebands occur in the large S power portion of the data since during this period R power is also quite large. As examples of the

50 0010 Hrs. 25 Nov. 1970 - R =110 _. R=114 I t i I I I I I,', I - I I I,, R = 102 R = 108 I I t I IJ I I 1 I I [I,J I I! R = 108 R =100 * * I I I I l I i 1 I 1 I...!,,. 20dB R = 110 R = 110 I ] I I, I I I,. I I II -0.4Hz 0 0.4Hz (a) Fig. 24. Reverb spectra displays: Fowey Rocks to Bimini

51 2036 Hrs. 25 Nov. 1970 R -116 -R = 110 R =114 R - 108 I i I I, I I I I I I 1_1_,1t 1.....!.. I 20dB R = 106 R=112 T, [ I I -t I I I I I I I, I -0. 4Hz 0 0. 4Hz (a) (b) Fig. 24. (Cont.)

52 R = 110 - - R = 106 I I1 I., I I I I I l I I,, I R = 108 R = 104 1 1 1 1 1 1 1 I 1 I I 1, 1, R = 106 R = 100 20dB R = 102 R = 100 I. 11. I IlI[_1I I I III I I -0.4Hz 0 +0.4Hz (b) Fig. 24. (Cont.)

53 reverb displays during this period, two sequences of displays taken over different 6-hour intervals appear in Figs. 24(a) and 24(b). The first display in the upper left-hand corner of Fig. 24 was taken at 0010 hours on 25 November. The first display in Fig. 24(b) was taken at 2036 hours, also on 25 November. Successive displays in all of the sequences of displays illustrated in this section are taken at 30 minute intervals. The value of R power at the time when each display was taken is written to the left of the display. It is seen from Fig. 24 that the amplitude of the reverb sidebands depends on the value of the corresponding R-power measurement. For these displays it appears that the reverb sidebands are centered about +0. 2 Hz on either side of the carrier with most of the power in each sideband confined to a 0. 2 Hz bandwidth. Although the largest reverb sidebands occur during the high S-power portion of the Bimini data, there are also periods from the stable S-power data during which reasonably well-defined reverb sidebands appear. Figure 25 illustrates two, 4-hour sequences of reverb displays taken from different periods of the stable S-power data. The first display in the sequence in Fig. 25(a) was taken at 0400 hours on 14 November and the first display in Fig. 25(b) was taken at 0255 hours on 18 November. As above, the amplitude of the reverb sidebands depends on the corresponding value of R power. In contrast to the reverb displays taken from the high S-power data,

54 0400 Hrs. 14 Nov. 1970 0300 Hrs 18 Nov. 1970 R = 100 R = 94 I I I I I I I I I I I I I I I I I I R = 100 ~* " ""R = 92 I I, I I 1 1 1i, i, I l i I R =102 R = 92 I i i 1 I i _ 1 1 I I I.... 20 dB AL * R 102 R = 92 T _ _ I I I I I I I I I-I I I I I4 I -0.4Hz 0 +0.4Hz (a) (b) Fig. 25. Reverb spectra displays: Fowey Rocks to Bimini

55 however, the bandwidth of each sideband is only about 0. 1 Hz. Also note that the center frequencies of the reverb sidebands in Fig. 25(a) are from 0. 05 to 0. 1 Hz larger than the center frequencies for the other Bimini reverb spectra. The reverb displays in Fig. 25 are typical of much of the stable S-power Bimini data, although there are long periods in this portion of the data where no noticeable reverb sidebands appear. The reverb spectra from the 7-mile data generally have a more definite structure than do those from the Bimini data. The amplitudes of the sidebands are larger and the shape of the sidebands varies less during the course of the experiment. Figures 26(a) to 26(d) illustrate four sequences of reverb spectra taken on four different days. (The time when the first display in each sequence was taken is indicated at the top of the display. ) The amplitudes of the reverb sidebands in these displays ranges from 10 to 25 dB and the sideband center-frequencies vary between + 0. 12 to + 0. 25. These reverb displays illustrate the complete range of behavior of the 7-mile reverb spectra. 2. 3 The Multipath Structure Displays The displays of the multipath structure are obtained as the magnitude of the cross-correlation between the demodulated reception and a pulse-compression reference (see Section 1. 3). The length

56 1300 Hrs. 17 Nov. 1970 1100 Hrs. 20 Nov. 1970 R =84 L R = 83 I I I I I i 1 11111 R =89 R =101 R = 85 - R =83 I i I L I I.... I I I I I I I I 1 1 20 dB R = 83 ~ R_ R =864L -1~R -. 86 I I I I I I I 1 i I I 1 -0.4Hz 0 +0,4Hz (a) (b) Fig. 26. Reverb spectra displays: Fowey Rocks to 7-mile

57 0930 Hrs. 24 Nov. 1970 1430 Hrs. 27 Nov. 1970 R = 88 - R = 88 R = 90 R = 85 * I I I,II I I, I I1 I I I R =85 R =88 20dB _4 R = 84 R = 83 I I I I I i -0.4Hz 0 +0.4Hz Fig. 26. (Cont.)

58 of the time delay axis in these displays is equal to the period of the transmission, 1. 2 seconds, and the duration of a single peak in the display is 2d = 0. 038 seconds. (The duration of a single peak is indicated on the display in the lower left-hand corner in each figure.) The vertical scaling for the multipath displays is determined only up to a factor which is a power of two. Thus, care must be used in comparing the relative strengths of arrival peaks in different displays. The multipath displays from the Bimini data indicate a wide variation in the complexity of the multipath structure. The most complex structure occurs during the period of stable S power. Figures 27(a) and 27(b) illustrate two sequences of multipath displays taken from this portion of the Bimini data. The multipath displays in Fig. 27(a) were taken from the shallow water data at 5-minute intervals beginning at 0050 hours on 16 November. The corresponding values of S power appear to the left of each display. There are two main arrival peaks occurring close together, preceded by a varying number of small amplitude arrival peaks. The overall power in the minor arrival peaks is the greatest for the small value of S power. The multipath displays in Fig. 27(b) were taken from the deep water data at 5-minute intervals beginning at 0352 hours on 14 November. The multipath structure in these displays is quite complicated. Each display shows many transmission paths, all of approximately the same strength. Although a significant portion of the Bimini

59 0050 Hrs. 16 Nov. 1970 0350 Hrs. 14 Nov. 1970 ~~S~~~~~~ = 112 S = 10= = S=114 S =112 =114 S=108 S=112 2 S = 112114 2dV S= 112 (a) (b) Fig. 27. Multipath structure displays: Fowey Rocks to Bimini

60 data has a multipath structure as complicated as that appearing in Fig. 27(b), there are only a few instances where the multipath structure becomes more complicated. The least complicated multipath structure occurs during the high S-power portion of the Bimini data. Figure 28 illustrates a sequence of multipath displays taken every 30 minutes beginning at 0010 hours on 25 November. For the high values of S power, the multipath displays indicate only one major arrival peak, and in several of these displays there are no smaller arrival peaks at all. For the lower values of S power, however, more than one major arrival peak appears. The multipath displays from the 7-mile data are less complicated and more stable than those from the Bimini data. Figures 29(a) to 29(d) illustrate four sequences of multipath displays taken on different days. The times at which the first display in each sequence were taken are the same as those for the reverb spectra in Fig. 27. The successive display in each sequence were taken at 15-minute intervals. It is seen that with few exceptions, each display indicates one major transmission path preceded by from two to four minor transmission paths. This behavior is typical of the 7-mile data multipath structure.

61 0010 Hrs. 25 Nov. 1970 S = 112 1S = 122 S = 108 S 118 S= 110 S =112 A. 114 S = 110. = 1 1 8 I = _ 10 S = 114 S = 116 S =- 110 S = 116 S118 S = 116 S=122 S = 116 t —- 1. 2 sec. ---- Fig. 28. Multipath structure displays: Fowey Rocks to Bimini

62 0810 Hrs. 25 Nov. 1970'S = I 16 S = 104 JS = 116 S = 104 S = 108 = 100 a s = 108 = 112 S = 108 S = 114 S = 104 jS = 112 S 106 S:= 112 S = 106 S = 110 2d s=106 S=106 I —--- 1.2 sec. —Fig. 28. (Cont.)

63 1810 Hrs. 25 Nov. 1970 S = 106 S = 120 S = 106 1 S = 116 Vi ^ ^J'LAA^/_________ _.__, S = 110 AS = 11 S = 110 S = 112 P = 114 S = 110 ^- - -, J> _ -e _ 118 s = 116, S =120 S =114 S=122 S = 110, -it- 2d _i:=120 S =104 __ - 1-.- _ A._. L* —-- 1.2 sec. ---- Fig. 28. (Cont.)

64 1300 Hrs. 17 Nov. 1970 1100 Hrs. 26 Nov. 1970 S =102 = 105 S =104 101 S =99 E = 101.....,. iii j S = 101, s = 100 S=103 ^A s= 100 S 103 = 100 S =102 S=98 S = 103 S =99 -A 2d S =102 S = 100 t —- 1.2 sec. (a) (b) Fig. 29. Multipath structure displays: Fowey Rocks to 7-mile

65 0930 Hrs. 18 Nov. 1970 1430 Hrs. 27 Nov. 1970 S -= 99 1S =106 S =103 S=107 F 105 S =106 S = 106tS= 105 S =105 8 = 106 S = 99 S =105 S = 98 = 105 S = 102 1S =10 A-2d | S = 100S = 106 r —--- 1.2 sec. ---- (c) (d) Fig. 29. (Cont.)

66 2. 4 Environmental Measurements During the course of the experiment, water temperature and tide level readings were made at the Bimini receiving site. Also wind speed and direction at Bimini were recorded during much of the experiment. In this section we present the results of these measurements along with a general description of the weather conditions during the experiment. Other environmental measurements were also made at the Miami receiving site, but the results of these will be deferred to a later report. With the exception of two cold periods, the weather during the experiment was generally mild with daytime temperatures in the mid 70's and light breezes ranging from 3 to 15 knots. The first of the two cold fronts reached Bimini around noon on 15 November, bringing cool, windy weather which lasted through 18 November. During this time, the daytime temperatures were in the mid 60's and the winds were between 10 and 22 knots out of the northwest. The second, and most severe cold front began on the evening of 23 November and lasted until 25 November. During this time the daytime temperatures dropped into the low 60's and the winds ranged from 15 to 30 knots out of the northeast. The water temperature readings at the Bimini receiving site were taken from a thermistor string located approximately one mile from shore. The five different readings, labelled T1, T2, TQ, Tq,

67 and T5, were taken at depths of 118 ft., 348 ft. 486 ft., 624 ft. and 759 ft. respectively. Plots of these readings appear in Fig. 30. The Bimini tide level was measured in feet above a reference point at a post located several yards from shore. The plot of these measurements appears in Fig. 31. The wind velocities in knots for those days when the measurements are available is also indicated in Fig. 31. 2. 5 Summary of the Preliminary Analysis The Bimini Data. At the Bimini receiving site, 4 days of data were taken from the deep hydrophone and 11 1/2 days of data were taken from the shallow hydrophone. These periods, along with the times on the other main events that occurred at the Bimini receiving site,are illustrated in Fig. 32. We consider the deep hydrophone data first. The general behavior of the three signal powers C, S and R does not change during the deep hydrophone data even during the cold weather period that occurred between 15 November and 18 November. The carrier power suffers sharp, deep fades occurring at an average rate of about one fade per hour. The sideband power is reasonably stable with local variations confined to a 10 dB range. Reverb power is also quite stable with its load variations also limited to a 10 dB range, although the frequency of these variations is greater than those in S power. Typical signal-to-noise

TEM PE RAU ( C) D: ~C',O~ ~ ~ co )Ir ~ < I ^

Ft. 4 3 2 15-18 10-15 3-5 NW NW 1_ SE-SW 10 11 12 13 14 15 16 17 18 19 20 21 DATE Nov. 1970 Ft. 4 3 2 10-15 15 E 15N, 25NE, 25NE 10-15 E E-NE 22 23 24 25 26 27 28 29 30 DATE Nov. 1970 Fig. 31. Tide level at Bimini

70 [,txkX\x\x Deep hydrophone data /////j^ Shallow hydrophone data: Stable S power KgZ~XXW g Shallow hydrophone data: High S power 1st cold period 2nd cold period _I 14' 15' 16' 17' 18' 19' 20' 21' 22' 23' 24' 25' 26' 27' 28 DATE Nov. 1970 Fig. 32. The times of the main events at Bimini ratios for C, S and R power are 40 dB, 20 dB and 3 to 10 dB respectively. The reverb spectra from much of the deep hydrophone data do not have measurable sidebands although there are a few periods during the first cold front when sidebands do become noticeable with amplitudes as large as 10 dB. The multipath displays generally exhibit a complicated structure with many arrival peaks. The most significant feature of the deep water noise power is the abrupt 15 dB increase that occurs on 15 November. The time at which this jump occurs coincides with a sharp increase in the wind velocity as the first cold front reached Bimini, suggesting that the

71 added 15 dB of noise power can be attributed to surface noise. After the jump occurs, N power becomes extremely stable with local variations (excluding shipping noise spikes) confined to a 3 dB range. Before the jump, N power is considerably less stable. The shallow hydrophone data, with the exception of the noise power, is best described by considering the periods of stable S power and the periods of high S power separately. During the stable S-power period, the three signal powers C S and R have the same general behavior as the signal powers from the deep hydrophone data. In fact, the only noticeable difference is that the local variations in R power are slightly more dramatic than those in the deep hydrophone R power. Typical signal-to-noise ratios for C, S and R are 40 dB, 15 dB and 5 to 10 dB, respectively. The reverb spectra and multipath displays from this period also have the same general structure as those from the deep hydrophone data. During the high S power period, all three signal powers C, S and R are from 10 to 20 dB higher than at other times. The carrier power fade rate drops to as low as one fade per six hours. Sideband power becomes considerably less stable and all three powers are highly correlated. The signal-to-noise ratios for C, S and R reach highs of 50 dB,, 35 dB and 25 dB respectively. The second cold front began about one day before the most dramatic period of high S power. When S power reaches its highest

72 values, the water temperature reading closest to the surface, T, reaches its lowest values, thus suggesting that at least some large increases in S power may be due to increased surface ducting The reverb spectra from the high S-power period generally have well defined sidebands with amplitudes between 5 and 20 dB depending on the corresponding level of R power. The multipath displays indicate only one major transmission path with at most only a few minor transmission paths. The clarity and stability of the multipath displays are greatest when the corresponding S power is large. The noise power from the shallow hydrophone data exhibits several distinct kinds of variation in addition to shipping noise. As in the shallow hydrophone noise power, there is a sharp 15 dB jump of surface noise that occurs as the wind velocity increases at the beginning of the second cold front. Also there is a series of 10 to 15 dB "rolls" in the mean level of the noise power many of which occur in a regular diurnal pattern suggesting a biological origin. Finally, there is a short 6-hour period during which large closely spaced spikes occur. The 7-mile Data. The 7-mile data exhibit much greater stability than do the Bimini data.. The mean power levels and the reverb and multipath displays show little variation, even during the cold weather periods. The carrier power fades although as severe

73 as the Bimini carrier power fades, occur only about half as often. The sideband power is almost identical in behavior to the Bimini deep hydrophone sideband power. Typical signal-to-noise ratios for C and S power are 30 dB and 50 dB respectively. Although the mean reverb and noise powers are considerably more stable than those from the Bimini data, there are many periods where large, closely spaced spikes occur. (This happens only once for a short period in the Bimini noise power and not at all in the Bimini reverb power. ) Moreover, these spikes often, although not always, appear in both the 7-mile power measurements at the same time. The reverb displays from the 7-mile data resemble those from the high S-power periods of the Bimini data. Reverb sidebands with amplitudes ranging from 5 to 10 dB and center frequencies between + 0. 1 and + 0. 25 are consistently evident. The multipath displays, almost without exception, show one major transmission path, preceded by at most 3 minor arrival peaks.

APPENDIX A Appendix A contains the constant gain x bandwidth plots of the carrier, sideband reverb and noise powers from the Bimini data. 74

140 CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, DEEP 130 120 110 100 dB 90 80 70 2 -------------- -— ~ 2 24 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 13 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, DEEP 140 130 120 110 dB 80 70 0 1 2 3 4 5 6 7 8 9 0 TIME (HOURS) 14 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, DEEP 140 130 120 110 100 dB 90 8070 13 14 15 16 17 18 19o 21 22 34 TIME (HOURS) 14 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMIN, DEEP 140 130( 120 dB 7( 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME(HOURS) 15 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, DEEP 140 130 120 110 100 dB 90 80 70 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 15 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, DEEP 140 130 120 110 a w dB dB 90 80 70 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 16 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, DEEP 140 130 120 110.tV u Iv I 1 100 0, dB 90 80 70 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 16 NOVEMBER 1970

CO1STANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, DEEP 140 130 120' lyrv7 0 IUU T- - ^v^~ ^Arv-r Kh~S~ClV~lr Y' 7 ^} /^ ^^^~l \ju.r K* dB 90 80 700 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 17 NOVEMBER 1970

140 CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, DEEP 130 V 120 110 100 dB 90 80 70 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 17 NOVEMBER 1970

140 CONTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110. 8B100 dB I 80 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 18 NOVEMBER 1970

FOWEY ROCKS TO BIMINI, SHALLOW CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIM 140 130 120 dB 9 8C 7( 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 18 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 140 130 120 M dB AIa 80 70 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 19 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 14 130 12 11 10 iB 9 8 7 - 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 19 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 140 130 12 11 10 - | dB 7( 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 20 NOVEMBER 1970

140 CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 -If 110100 c~0 dB 90 80 7012 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 20 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 140 130 120 100 dB 90 80 70 0 1 2 3 4 5 6 7 8 9 10 11 TIME (HOURS) 21 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 140 130 120 110 100 70 8L ~ li3 1~14 15 16 17 18 19 20 21 22 2 12TIME (HOURS) 21 NOVEMBER 1970 TIME (HOURS) 21 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 140 130 120 110 100 dB 70 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 22 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 140 130 120 110 100 dB 90 80 70 L,,.......,...I 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 22 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 140 130 120 1T0 1 2 NOVEMBER 1901 100 ORON dB 9 1 80 70 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 23 NOVEMBER 1970

140 - CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 4 110 pi v Ino-~~~c l I 0 100 dB V 80 70 12 13 14 15 16 17 18 19 20 21 2223 TIME (HOURS) 23 NOVEMBER 1970

140 CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 100 dB 90 80 70 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 24 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 140 130 | I | 120 110 100 dB 90' 80 70 12 13 (14 15 16 17 18 19 —- 20 - 21 22 23 2 TIME (HOURS) 24 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 100 d8 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 25 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 140 130 120 110 100 dB 90 80 70 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 25 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 140 130 120 110 dB 0 12 13 4 5 6 7 8 9 10 11 12 TIME (HOURS) 26 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 140 130 120 110 100 dB 90 \~~~~~~~~~~I i 80 70 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 26 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMIN, SHALLOW 140 130 120 110 100 1 dB 90 80 70 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 27 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 140 130 120 110 100 dB 90 80 70 12 13 14 15 16 17 18 19 2iO 227 NR 103 4 TIME (HOURS) 27 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCK TO BIMINI, SHALLOW 130 120 110,0 dB 8. O.. L 0 1 2 3 4 5 6 7 8 - 10 11 12 TIME (HOURS) 28 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 140 13 12 8( 7(T 12 I14STIME (HOURS)13 1 28 1NOVEMBER 2 19-70 TIME (HOURS) 28 NOVEMBER 1970

140 - CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO BIMINI, SHALLOW 140 SWHAL RO TO BIAIA 130 120 110 100 dB C 90 80 70 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 29 NOVEMBER 1970

APPENDIX B Appendix B contains the unity gain plots of the carrier and sideband powers from the Bimini data. 107

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, DEEP 140130 120 110 10~~~~~~~~~~~~~~~~~~~ dB 90 70 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 13 NOVEMBER 1970

UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, DEEP 140 130 120 800 dB 90 8 7 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 14 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI DEEP 130 120 110 100 - dB 90 80 70 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 14 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, DEEP 130 120 110 dB 90 80 70 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 15 NOVEMBER 1970

10 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, DEEP 140 130 120 110 100 dB 90 80 70 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 15 NOVEMBER 1970

UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, DEEP 140 130 120 110 I-L 100 dB 90 80 70 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 16 NOVEMBER 1970

UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, DEEP 140 130 120 110 100 dB 90 80 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 16 NOVEMBER 1970

140 - UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, DEEP 130 120 110 8070 0 1 2 3 4 5 -6 7 10 11 12 TIME (HOURS) 17 NOVEMBER 1970

140 p UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, DEEP 130 120 dB 90 80 N i I 70 12 13 -14 15 16 -17 18 19 20 21 22 23 24 TIME (HOURS) 17 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 I" 100 dB 90 80 70 0 1 2 3 4 56 7 8 NO 10 11 TIME (HOURS) 18 NOVEMBER 1970

140 - UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 100 in dB 90 80 12 13 14 15 1i 17 - 8 19 2 2i-23 24 TIME (HOURS) 18 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 dB 90 80 70 T 1 2 3 4 I5 6 7 8 9NOVEMBR TIME (HOURS) 19 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 100 0 dB 90 80 70 12 13 14 15 16 17 8 19222 TIME (HOURS) 19 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 100 LB 90 80 70 i 2-3 4 52TIM (H S 20 8NOVEMBER11 912 TIME (HOURS) 20 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 100 f: dB 90 80 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 20 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 dB 90 80 ~ yV n ~~~~~~~~I I p/ 70 ----- i ---- i ----- i ---- I ____ -____-_____ t - -_____ i _____ I ----- ~ --- I - ~ 0~1 2345 6 7 8 V9 10 6 72 TIME (HOURS) 21 NOVEMBER 1970

140 - UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 100 t3 dB 90 I ~ ~~~~~~~~~~~~~~~~~~~~~~~~IF 80 70 12 i3 14 15 16 17 18 19 20. 21 22 TIME (HOURS) 21 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 100 1' dB 90 80 70 TIME ( S)2 NOEE 1 0 3 4 567I 8 - 9111 2 TIME (HOURS) 22 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 dB TO - II_ 90 80 70 12 13 14 I 1' 19 20 21 22 23 24 TIME (HOURS) 22 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 100 A dB 90 80 70 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 23 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 ^ y/^^^ 100 dB 90 80 70 12 13 14 15 16 17 18 19 20 21 22 23 TIME (HOURS) 23 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 100 dB 90 80 0 1 2 3 4 5 6 i 8 9 10 -- 1; 12 TIME (HOURS) 24 NOVEMBER 1970 TIME (HOURS) 24 NOVEMBER 1970

140 j UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 130 100 0 dB 90 80 70 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 24 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 100 dB 90 80 70 0 1 23 4 5 6 7 8 9 10 192 TIME (HOURS) 25 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 100 -- o dB 90 80 70 12 13 14 S 1~1-TIME (HOURS) 165 NOVEMBER 19 7024 TIME (HOURS) 25 NOVEMBER 1970

140- UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 100 dB 90 80 70 o 1 z 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 26 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 100 dB 90 80 70 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 26 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 dB f 90 80 70 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 27 NOVEMBER 1970

140 - UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 100 dB 90 80 70 12 13 14 15 16 17 - 18 1 20 2 2 23 2 TIME (HOURS) 27 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 90 80 70 oi - s —-' 2 01 -— t1i 12 TIME (HOURS) 28 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 100 00 dB 90 80 70 12 1 15 16 17T 1M8 1(HOR9 20 2NOVEMBER 19 TIME (HOURS) 28 NOVEMBER 1970

140 UNITY GAIN PLOT FOWEY ROCKS TO BIMINI, SHALLOW 130 120 110 dB 90 80 07 2 3 4 5 6 8110 11 TIME (HOURS) 29 NOVEMBER 1970

APPENDIX C Appendix C contains the constant gain x bandwidth plots of the carrier, sideband, reverb and noise powers from the 7-mile data. 140

130 " CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MIL 120 110 100 dB 90 80 70 60 - 60-~~~ ( &12 13 14- 1 1i 1-7 I8 19 0 2 2 2324 TIME (HOURS) 13 NOVEMBER 1970

130. CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 120 100 IB 90 - " i " 80 70 600 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 14 NOVEMBER 1970

13 Co"ST'4VTGTj 120 FOWE y nRO 11 dB 90, r r rr~'~Y~ 7 Y IH~A 1 j 8 1 7~~~~~~~~~1 1 4~~~~~~~~~1 TIME (HOIO J 1n 14 IOV.EA/,13ER 1 9

130 r\ CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 60 0T 1 2 3 5 6 7 8 9O 197 0 TIME (HOURS) 15 NOVEMBER 1970

130 V CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 IJe 1 80 70 60 12 13 14 15 16 17 18O 19 20 222 23 24 TIME (HOURS) 15 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 130 120 110 100 dB 90 1 80 70 60 0TIME (HOUR) 16 N M 9 10 11 12 TIME (HOURS) 16 NOVEMBER 1970

130 - CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 1' Y 80 70 60 4TIME (HOUR)16 17 1 16 NOV R 21970 2 TIME (HOURS) 16 NOVEMBER 1970

130 W CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 80 70 60 0 1 4I 5 E -- H 8O10 17- O- 6M 129 TIME (HOURS) 17 NOVEMBER 1970

130 CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60 12 13_TIME 14 15 16(HO 17 E8 19 20 21 22 22 TIME (HOURS) 17 NOVEMBER 1970

130 - CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60 0?- i- 3 - 4 T 6 7- -) 1- -Nt —OV-I- TIME (HOURS) 18 NOVEMBER 1970

130 CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCK TO 7-MILE 80 130 P 70120 dB N 12 13 1 4L -12 13 14 15l —17 ^18 19 20 21 1 9 23 0i TIME (HOURS) 18 NOVEMBER 1970

130 CONSTANT GAIN BANDWIDTH PLOT FOWEy ROCKS TO 7-MILE 120 110. 100 I 1 N 17 dB 9c3C 80 vn 70 60 1 2~~~~~ TIME (HOURS) 7 --- 19 NOVEMBER 1970 1

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 130 120 110 100 dB 90 80 70 60 12 TM4 15 16 1H 18) 19 20 2 — - 22 — 23 124 TIME (HOURS) 19 NOVEMBER 1970

130 CONSTANT GAIN x BANDWIDTH PLOT, FOWEY ROC O 7- ME 120 110 100 dB 80 70 -Ac 60 0 2 TIME (HO RS) 2 8 1970 TIME (HOURS) 20 NOVEMBER 1970

130 CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 130 120 110 100 dB 90' cn 70 60 12 13 14 15 161 — 7 —- 19 20 21 22 —- 324 TIME (HOURS) 20 NOVEMBER 1970

130 CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 70 60 TIME1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 21 NOVEMBER 1970

3 CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60 12 13 14 116 17 1~8 1 9 20 21 r2- 2 ~2 TIME (HOURS) 21 NOVEMBER 1970

130 CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 g 80 60 TIME (HOUR) 22 NE 9 10 11 12 TIME (HOURS) 22 NOVEMBER 1970

130 CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 22 NOVEMBER 1970

0 CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 130 120 100 dB 90 80 70 60 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 23 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 130 120 110 100dB 90 o 80 70 60 12 13 14 15 16 17 18 19 20 21 22 23 14 TIME (HOURS) 23 NOVEMBER 1970

13 CONSTANT GAIN x BWIDTH PLOT FOWEY ROCKS TO 7-MILE 130 120 i00 dB 90 80 70 i 60 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 24 NOVEMBER 1970

130 CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 130 120 110 100 dB 90' < o 80 70 60 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 24 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 130 120 70 60 0 1 2 3 4 5 6 7 8 9 ------------— 2 TIME (HOURS) 25 NOVEMBER 1970

CONSTANT GAIN x BAIDWIDTH PLOT FOWEY ROCKS TO 7-MILE 130 120 110 100 dB 80 70 6012 1 22 23 24 TIME (HOURS) 25 NOVEMBER 1970

130- CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS 7- E 120 100 dB 90 * 80 70 60 0CTI 1 2 3 4 - -6 47 9 10 — — 2 TIME (HOURS) 26 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 13 120 11 dB 8 7 i 6T 12 13 14 15 16 17 18 19 20 2t1 22 23 24 TIME (HOURS) 26 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 130 120 11 dB 7 6C0 1 2 3 4 5 6 TIME (HOURS) 27 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 13 12 11 10 dB 6CJ~1~ 1 i I. 12 13 14 1 16 17 18 19 20 21 22 23 24 TIME (HOURS) 27 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 13 11 10 dB 7 6( 0 i 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 28 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 13 12 11 10 dB 8T ( 60, 12 1 141-516 7 1 8 19 2-0 2 22 2 TIME (HOURS) 28 NOVEMBER 1970

CONSTANT GAIN x BANDWIDTH PLOT FOWEY ROCKS TO 7-MILE 130 120 110 100 9 V, 80 70 60 0 i 2 - -. 6 7 8 9 10 11 12 TIME (HOURS) 29 NOVEMBER 1970

APPENDIX D Appendix D contains the unity gain plots of the carrier and sideband powers from the 7-mile data. 173

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60T O 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 13 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 80 70 60 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 14 NOVEMBER 1970

130- UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 9u o 80 70 60 12 13 14' —i- j-15 16-17 18 19 20 21 22 23 24 TIME (HOURS) 14 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 - 80 70 60 ~T0 I1 2 3 4 15 6 NO 11 12 TIME (HOURS) 15 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 i:- _W ^v _______, 80 70 60 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 15 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60 0 2 3 4 5 6 7 8 9 10D —-— ~1 —U51_0 _~ i 1 TIME (HOURS) 16 NOVEMBER 1970

130 - UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60.....T_ IM 1 _,_..(OR S _ 1 V E M B-.1.9 12 13 14 15 (16 17 18 19 20 21 22 23 24 TIME (HOURS) 16 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60 0 — 11 12 TIME (HOURS) 17 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 100 dB 110 80 70 60 12 13 14 15 16 17 18 19 20 21 22 23 TIME (HOURS) 17 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 18 NOVEMBER 1970

130J UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90I I 80 70 60 12 13 14 15 16 7 18 19 20 2 2 23 24 TIME (HOURS) 18 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7- MILE 120 110 100 v V dB 90 80 70 60 TIME (HOURS) 19 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60 12 13 14 15 1( S 97 HRS)19NOVEMBER1970 TIME (HO URS) 19 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 - 100 dB 90 I ti 80 70 60 TIME (HOURS) 20 NOVEMBER 1970

130 h UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 20 NOVEMBER 1970

130 - UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 00 80 70 60 0 1T2 3 4 5 6 7 8 9 1970 TIME (HO URS) 21 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60 12T 13 14 15 16 17 18 19 20NVEMBER 197 TIME (HO URS) 21 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60 1~~~~~~~~~~~~~~~~~~~~~~~~~1 0 1 2 4~~JYU~T (Hou-9 22 NOVEMBER 1970 TIME (HOURS) 22 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60 12 13-I 156 20 1f-9 22 2f~f'4 TIME (HOURS) 22 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60 -— TIME (HOURS —— ) 23 NOVEMBER 1970 —— ^ —---- TIME (HOURS) 23 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 ~~~ \ f V t I~~\ if l/ / 90 80 70 60 12 13 14 15 16 17 18 19 0 21 22 23 24 TIME (HOURS) 23 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 80 70 60 0 I 2 3 4 5 6 7 8 919 O TIME (HOURS) 24 NOVEMBER 1970

130 130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 24 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 g dB 90 80 70 60 O~ T 2 3 I4 5 6 7 TIME (HOURS) 25 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7 MILE 120 _ 110 dB 90 80 70 60' 12 - -. —-. —-__ _ I......L.1.~.. -..........._ —_. -.......IL. -.[~.1_.. 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 25 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60 --- -l ---- i.- --,,.:_ _ _|.-, 4 - -i —...-x-^..-..J- ---- JL -.- ^.- ^A --- -fas — * —* — ^ r.- --- -1Oi0 M2 3HUS4 5679I 2 TIME (HOURS) 26 NOVEMBER 1970

130 UMNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 0 80 70 60 12~~~~~~~~~~~~~~~~-,Y~ t-li 1*5"-"""fe 1 7 ]1 f^" ^ -- - -^ ~ _ —— ^ —— ^YL~y ~T12 13 14 1 6HS16 17 18 19 20 21 22 23 24 TIME (HOURS) 26 NOVEMBER 1970

130130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60 0 1 2 3 4 5 6 7 8 9 10 11 12 TIME (HOURS) 27 NOVEMBER 1970

130 - UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90-I k 80 70 60 _____.____~~~~~~~~.,.,____t-^__^j ___ I____I _____~_____ILYI-CL — Y-IYI ~I)II~-~IUI~~~ —-- ~-L — -— ~ —-- 12 13 14 15 16 17 18 19 20 21 22 23 24 TIME (HOURS) 27 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 70 60 TIME (HOURS) 28 NOV —---— EMBER 1970 —- — o —---- -. TIME (HOURS) 28 NOVEMBER 1970

130 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 80 - 70 60 12 13 14 15 16 17 18 19 20 21 2 24 TIME (HOURS) 29 NOVEMBER 1970

130 10 UNITY GAIN PLOT FOWEY ROCKS TO 7-MILE 120 110 100 dB 90 Ii 80 70 60 TIME (HOURS) 29 NOVEMBER 1970

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S'ciz~tt Clmr w"Fleflonn DOCUMENT CONTROL DATA. R, D (.T~.orr..ty rli*ifflrafton nf tiote, hory nf h.fnrrt rand Indelng oannolatln, sn.oIti bhenf.ternd when. the overall report fi!nelled) OR~0~NA TINO AC tIVI TV f(Crporete author) 29. RIEPORT SECURITY CLASSIFICATION Dooley Electronics Laboratory Unclassified| Jniversity of Michigan 2h. GROU nn Arb.or., Michigan 48105 |. RAEPOT t TLt' Jnderwater Sound Propagation in the Straits of Florida: The Preliminary Analysis )f the MIMI Experiment of 1970 DESC RPTIVE' MO.Tht (Type of report and Inchlo ve datel) rechnical Report No. 213 -- 036040-7-T February 1972 AU tHOlS) (firat name, middle Inltlfll, tla name) Richard M. Heitmeyer RIEPORT oDA Tat. TOTAL NO. OF PAGES?tb. NO. OF REFS February 1972 219 C. CNTRACT OR GRANT NO. 9O. ORIGINATOR'S REPORT NUMBER(S) J00014-67-A-0181-0032 TR213 PROJECT NO. 9b. OTHER REPORT N0(-) (Any other numbers that may be asesigned thia report) 036040-7-T ___________________,__Arlington, Va.,22217'ABSTRACT AT AnC underwater acoustic propagation experiment was conducted during he month of November 1970 as part of the Project MIMI propagation and signal Processing research program. A periodic broadband signal, modulating a 420 HZ:arrier was transmitted continuously across the Straits of Florida for 19 days. it the receiving site, the power and phase angle of the carrier, the power in the -ignal sidebands, and the noise power in the signal band were measured. In addition, he total power and the power spectrum in a narrow band about the carrier line vere determined as a measure of the modulation due to the forward-scattered surace reverberation. Finally, the correlation of the received signal with a stored reference was computed to measure the multipath structure and its stability. This'eport presents a brief description of the acoustical range, the experiment, and the ireliminary analysis of the data. D,'C"i..1i473ct Security Classification

Security Classification 14. LINK A LINK B LINk C KEY WORDS N 111O L E WT ROL WT- R0 L E -L W T Signal processing Underwater sound Multipath Surface reverberation ml. inin -, S_, _ _~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~r

UNIVERSITY OF MICHIGAN 3 901 5 03026 8034II 3 9015 03026 8034