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Jun 1977

Volume 61, Issue S1, pp. S1-S96

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back to top Session C. Physiological Acoustics I: Deafness, Audiometry
Contributed Papers
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Mouth/voise synthesis for lipreading research (A)

Norman P. Erber and Carol Lee De Filippo

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S6-S6 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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Relative onset times of voicing and visible articulation are potential cues for lipreaders to recognize nasal/stop consonants. For bilabials, a phototransistor behind the teeth and an external microphone indicated mouth opening and voice onset, respectively. Average voice leads for ten adults were: /ma/, +66 msec; /ba/, −1 msec; /pa/, −8 msec (/ma‐ba/ boundary, +28 msec; /ba‐pa/ boundary, −18 msec). To test relative voice/mouth onset as a perceptual cue. we produced synthetic syllables: the face substitute was an oscilloscope pattern, forming a mouth shape for 250, 400. or 550 msec; the voice substitute was a vowel‐like buzz delivered through a hand‐held vibrator. Buzz accompanied mouth opening with lead times of +200 to −200 msec (40 msec steps), and ended simultaneously with mouth closure. Normal‐hearing observers labeled each combination “ma” “ba.” or “pa.” Practiced lipreaders with knowledge of the onset cue subdivided the continuum with boundaries at +82 msec (ma‐ba) and −87 msec (ba‐pa). Because articulatory and perceptual boundaries are not coincident, this combined‐mode cue appears insufficient unless performance can be improved through training.
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Development of directional responses toward sound by young guinea pigs (A)

Jack B. Kelly and Maureen Clements

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S6-S6 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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Infant guinea pigs were tested in a circular apparatus for their tendencey to approach the source of auditory stimulation. A tape recording of guinea pig vocalizations was played over a loud speaker and the incidence of directional responses was noted. Even without external reinforcement there was a tendency to approach the particular stimulus used in this study within the first four days after birth. In order to determine the cues involved in infant localization, animals were tested with wax plugs inserted in one ear or in both ears. The plugs attenuated but did not totally eliminate sound entering the ear. Directional responding was reduced to chance by monaural blocking, but not by binaural blocking. Similar results were obtained with older animals eleven to thirty‐one days of age. Furthermore, directional responding was impaired in animals raised from birth with monaural ear plugs, but tested without ear plugs. These results indicate that sound localization occurs early in development in the guinea pig, that binaural cues are important, and that monaural deprivation can affect subsequent responding.
back to top Session D. Speech Communication I: Distorted Speech, Deaf Speech
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Underwater speech intelligibility as a function of fundamental frequency, speech rate, and intensity (A)

J. W. Hicks, Jr.

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S6-S7 (1977); (2 pages)

Online Publication Date: 11 Aug 2005

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Previous investigations have demonstrated that divers can improve their speech intelligibility in the underwater milieu. However, little or no information specifying the parameters involved in such improvement is available. This study attempts to objectively evaluate the accuracy of divers' ability to systematically and independently manipulate the speech parameters of intensity, rate, and speaking fundamental frequency and to study the effect of these changes on speech intelligibility. Divers were trained to vary each speech characteristic individually (high and low levels for intensity and speaking fundamental frequency; fast and slow rates) while reading Griffiths word lists. Voice recordings were made at depths of 0, 30, and 300 ft. Intelligibility scores were obtained via standardized listening sessions carried out at the Institute for Advanced Study of the Communication Processes. The results indicate that the diver/subjects were able to manipulate the speech parameters with a good degree of accuracy, i. e., shifting each parameter in the correct direction while holding the others constant. While there was a tendency for low f0, high intensity, and slow rate to improve intelligibility, the magnitudes of these trends were not statistically significant.
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Intracabin communication in light aircraft noise: subjective evaluations and talking levels (A)

J. A. Rupf

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S7-S7 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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As part of a study of factors affecting ride quality, the effect of general aviation cabin noise on speech communication between passengers was investigated. Twelve female subject pairs were seated side by side and required to converse with each other while being exposed to 5‐min segments of noise. Three different noise types were presented at levels of 90, 85, 80, and 75 dB(A). After each noise segment, the subjects rated the noise effect on conversation, judged the noise as acceptable or not acceptable for conversation, and estimated how long they could converse comfortably in the noise. Fifty percent of the subjects judged 75 dB(A) as acceptable for conversing 1 h or longer. Throughout all testing, the subjects wore small boom mikes, which were attached to eyeglass frames, and measurements of talking level were made. A regression line fit to the entire data set showed a 6.4 dB(A) increase in talking level for a 10 dB(A) increase in noise level. Corresponding regression line slopes for individuals varied from 5.0 to 7.8 dB(A). [Work supported by NASA.]
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Required attention for synthesized speech perception for two levels of linguistic redundancy (A)

C. A. Simpson and S. G. Hart

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S7-S7 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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It was hypothesized that additional contextual linguistic redundancy in the wording of synthesized speech cockpit warnings would result in less required attention for initial comprehension and subsequent recognition. Twelve airline pilots were repeatedly presented 16 unfamiliar warnings in two wording formats, key word and sentence; e.g., Fuel low, compared to The fuel pressure is low. Then they heard the same warnings embedded in weather broadcast at a warning‐to‐weather sound pressure level ratio of +3 dB. For both listening conditions the task was to read back the message and also estimate the passage of time during message comprehension or recognition. Peformance on time estimation had previously been found to correlate with hypothesized attention demands during manual tracking and aircraft simulator flying tasks. As expected in the present study, intelligibility was higher and response time shorter for the sentence format than for the key word format. For unfamiliar messages, the tendency to underestimate the passage of time was greater for the two word format than for the sentence format, implying that less attention was available for the time estimation task during comprehension of messages with less linguistic redundancy. By contrast, for familiar messages there was no significant difference in performance on the time estimation task for the two levels of linguistic redundancy. Possible reasons for the difference in attention requirements for comprehension compared to recognition will be discussed. [Work supported by NASA Grant NGL 05‐046‐002 to the San Jose State University Foundation.]
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Effects of noise on short‐term memory of consonants (A)

M. P. Rastatter, J. L. Danhauer, and G. Herman

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S7-S7 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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The purpose of this study was to investigate intrusion errors for consonants in short‐term memory (STM) when perceived in varying signal‐to‐noise (S/N) ratio conditions. Stimuli were eighteen English consonants paired with the vowel /a/, and presented in groups of nine blocked in threes. Twenty‐seven phonetically trained college students were separated into three groups of nine subjects each. Subjects in each group heard the stimuli in either (1) 0 dB S/N, (2) −5 dB S/N, or (3) −10 dB S/N ratios (re MCL); transcribed their responses; covered them; and recalled items from STM. A paradigm described earlier [W. Wickelgren, J. Acoust. Soc. Am. 39, 388–398 (1966)] was used for stimulus presentation and recording of results. Subjects' error data were submitted to INDSCAL and analyzed for distinctive features. Features were compared across noise conditions and to earlier studies. Data were also analyzed in terms of number correct.
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Changes in speech as a function of alterations in the oral and auditory environment (A)

S. R. Garber, T. M Speidel, and L. Glass

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S7-S7 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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Speakers may be forced to alter their speech and physiological patterns when they are fitted with a dental prosthesis. In the present study, speech alterations were assessed as a function of the speech task, the dimensions of the prosthesis and the speaker's auditory environment. Each of 24 normal subjects read lists of syllables, words, and sentences and spoke spontaneously while wearning no prosthesis, a thin (1.5 mm) prosthesis covering the entire palate, and a thick (3 mm) prosthesis covering the palate. All tasks were completed in quiet and in the presence of a 90 dB SPL speech noise. In a variety of acoustic and perceptual analyses, speech deteriorated as the thickness of the prosthesis increased, and when noise was presented. There was no interaction between the effects of the noise and the prostheses on speech. Although differences between conditions generally reached statistical significance, subject variability was striking. [Work supported by an NIDR postdoctoral fellowship awarded to S. R. Garber.]
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Coarticulatory effects in speech adaptation (A)

S. L. Hamlet and M. Stone

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S7-S7 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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Experimental prosthodontic modification of alveolar contour induces a compensatory form of articulation. The initial effects on speech, noticeable particularly during the first few days of adaptation, are heard as lisping and a general indistinctness in articulation. After two weeks of adaptation, when articulatory compensations have been learned, the speech of most subjects sounds essentially normal. It would seem that the reorganization in this motor task must involve a reestablishment of subtilties in articulatory coordination. Data on jaw motions and tongue/palate contacts were analyzed to see the extent to which coarticulatory phenomena in VCV environments would be preserved in initial attempts to speak with a prosthesis and after adaptation to it. [Work supported by NIH.]
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Mothers' simplification of phonetic input to their children in English and Polish (A)

Barbara J. Moslin and Patricia A. Keating

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S7-S8 (1977); (2 pages)

Online Publication Date: 11 Aug 2005

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Voice onset time measurements were made of three mothers' productions of word‐initial spiral stops to their 18 month old children in order to determine whether mothers play a significant role in their child's acquisition of the voiced—voiceless distinction. Two of the mothers spoke native English to their children, and one spoke native Polish. Measurements were also made of each mother's productions of word‐initial stops to another adult. Results show that mothers speak differently to their 18 month old children than they do to other adults. All three mothers employed certain clarification strategies for reducing the overlap of VOT values between voiced and voiceless categories which exists in normal adult adult discourse. These strategies included an increase in the median VOT values for productions of the voiceless stop, and/or a reduction in the range of VOT values for the voiceless category. Mothers, therefore, seem to be facilitating the task of phonological acquisition for their children by presenting them with a maximally distinct, tailored phonetic input. [Work supported by NICHD.]
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Voicing in the speech of language‐delayed children (A)

Z. S. Bond and Howard F. Wilson

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S8-S8 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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Voicing as a phonological contrast emerges relatively early in the speech of children learning English. However, the acoustic realization of this contrast is quite complex. The purpose of this study was to investigate the details of the control of the voicing contrast in the speech of 10 children diagnosed as language‐delayed in comparison with the speech of 10 children developing language normally. Each child was given a short test to determine if he could respond appropriately to minimal pairs differing in the voicing of stop consonants, and then recorded repeating 12 test words. Spectrograms of the three best productions of each word were analyzed, examining VOT differences between voiced and voiceless stops in initial position and the duration of the vowel preceding the stop pairs in final position. For all children, the control of VOT seemed to be in one of three stages of development: (1) overlap, (2) little overlap but great variability, (3) little overlap and decreased variability. A similar pattern of development, involving a decrease in overlap with a subsequent decrease in variability, was observed for vowel duration. Neither VOT nor vowel duration values comparable to adult values were achieved by the children.
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Correction of deviant timing patterns in deaf children's speech using computer techniques (A)

M. J. Osberger

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S8-S8 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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Research has shown that deaf children typically distort the temporal patterns of speech. Data obtained by John and Howarth [Lang. and Speech 8, 127–134 (1965)] indicate that incorrect timing patterns may have a detrimental effect on the intelligibility of deaf children's speech. However, the results of this study have not demonstrated the individual effects of phonemic and timing errors on speech intelligibility. The present paper is a progress report which describes the techniques used to correct deviant timing patterns in deaf children's speech. Six sentences produced by six deaf children have been selected for manipulation using digital speech processing techniques. The 36 utterances have been segmented on a phoneme‐by‐phoneme basis using an interactive computer facility that allows for segmentation simultaneously by ear and by eye from a visual display of the waveform. The same sentences produced by normal hearing children also have been segmented in order to obtain normative duration values. Adjustment of the segment duration has been accomplished by adding or subtracting whole pitch periods from steady‐state portions of the phonemes. Using a six stage approximation procedure, the deaf children's speech has been processed so as to systematically approach the timing patterns typical for normal hearing children. [Research supported by PHS Grant NS 09252.]
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Children's speech discrimination in quiet and noise (A)

L. L. Elliott, S. T. Connors, C. C. Wier, E. A. Kille, and S. Levin

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S8-S8 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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Normal children 5–8 years old, were tested on a new speech discrimination procedure. Stimuli were monosyllabic nouns within the receptive vocabularies of three‐year‐old inner‐city children. An up—down procedure tracked the 71% correct level of response. Open‐ and closed‐set conditions were tested. Closed‐set conditions used four‐alternative picture responses. Subjects were tested in quiet with an open response set (no pictures) and then on three closed‐set conditions: quiet, with a 12‐talker‐babble masker at 70 dB SPL, and with a filtered‐noise masker (filtered to have the same spectrum as the babble) at 70 dB SPL. Thresholds in babble were about 10 dB higher than thresholds in noise, and open‐set quiet thresholds were about 10 dB higher than closed‐set quiet thresholds. No age differences were observed. The absence of an age effect with the monosyllable stimulus items contrasts with an earlier report [L. L. Elliott, J. Acoust. Soc. Am. 60, S28 A (1976)] where there was an age effect for older children tested in noise on a linguistically more complex task. [Supported by BEH.]
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Phonemic errors of deaf children on a nonsense syllable test (A)

N. S. McGarr, H. Stromberg, and I. Hochberg

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S8-S8 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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A closed response nonsense syllable test was developed to assess the reception of gross phonemic contrasts by deaf children. Test items were composed of V, VC, and CV syllables with the vowels /i,a,u/ and the consonants /m,s,g/. The test was administered over a two‐year period (1975 and 1976) to one hundred 12–14 year old deaf children enrolled in schools for the deaf throughout New York State. Percentile plots showed improvement in overall performance over the two‐year period. Greatest improvements were for vowels. Results indicated a pattern of errors similar to those reported by previous investigators for adults and adolescents [Pickett et al., in Speech Communication Ability and Profound Deafness, 119–133 (1970)]. These included: (1) scores for vowels were consistently higher than those for consonants, (2) scores for /u/ and /a/ were roughly the same and were in turn higher than the scores for /i/, (3) scores for the initial consonants were higher than scores for final consonants except for the nasal in which the reverse was true. [Work supported by Cooperative Research Endeavors in Education of the Deaf (CREED), Bureau for Special School Supervision, Office for Education of Children with Handicapping Conditions].
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Listeners' impressions of speakers with and without hearing losses (A)

G. W. Blood, I. M. Blood, and J. L. Danhauer

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S8-S8 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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The purpose of this study was to evaluate listeners' ratings of normal hearing and hearing‐impaired speakers' on the following four a priori factors: intelligence, achievement, personality, and appearance. Additionally, alterations in listener ratings were investigated as a function of whether or not subjects wore hearing aids regardless of speaker types. Recorded speech samples of four normal hearing, four hard of hearing, and four deaf children were used as audio stimuli; and two photographic slides of each child (one showing him wearing a hearing aid, and one showing him not wearing a hearing aid) served as visual stimuli. The stimuli were heard and seen by 150 normal listeners who rated various characteristics of the speakers on a semantic differential scale. Ratings were submitted to a multivariate analysis which revealed that listeners' impressions of speakers were “more negative” both when the speaker had “hearing‐impaired” speech and when his photograph showed him wearing a hearing aid.
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Experimental results on Tadoma (A)

C. M. Reed, N. I. Durlach, L. D. Braida, W. M. Rabinowitz, S. Norton, M. C. Schultz, and C. Chomsky

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S8-S9 (1977); (2 pages)

Online Publication Date: 11 Aug 2005

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We have initiated a study of speech perception through the Tadoma method of speechreading. In this method, currently used by a small number of deaf—blind individuals, the receiver places his hand on the face and neck of the speaker and monitors various aspects of the articulatory process to understand speech. Our studies have involved one highly trained Tadoma user as well as several untrained, normal subjects. Experiments have been carried out to determine the general speechreading abilitites of the experienced Tadoma user, to compare performance of trained and untrained subjects on simple discrimination tasks, and to specify cues used in the perception of phonemes through Tadoma. Some results from these studies will be presented and discussed.
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Continued evaluation of a multipoint electrotactile speech aid (A)

D. W. Sparks, P. K. Kuhl, A. E. Edmonds, G. P. Gray, M. Bourgeois, B. Wiedmer, J. Gray, and L. A. Ardell

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S9-S9 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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At the 92nd meeting of the Acoustical Society of America, we reported preliminary data on vowel and stop and nasal consonant recognition using our multipoint electrotactile speech aid (MESA). Speech tokens were presented to artifically deafened adults who were required to identify the tokens in three conditions; tactile presentation, visual presentation, and tactile plus visual presentation. This report will be an update on our continuing evaluation of the speech transmission capabilities of the MESA. Specifically, we have extended our tests to fricatives, stops in final position, vowel recognition across talkers, segmental and suprasegmental features within a sentence context, and, finally, connected discourse. While the MESA demonstrates excellent resolution for certain speech features, we will discuss m‐difications of the MESA designed to enhance its transmission of those features not well resolved.
back to top Session E. Shock and Vibration I: Machinery Noise and Vibration Monitoring
Invited Papers
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Proposed shipboard noise and vibration monitoring system (A)

Adamandios G. Gafos

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S9-S9 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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In this paper the composition, operation, and performance capabilities of a shipboard noise and vibration monitoring system will be described. The uniqueness of this system is that it consists of readily available off‐the‐shelf instrumentation designed to measure or monitor both the mechanical and/or acoustic condition of shipboard machinery. For this particular application the system has been tailored for use aboard a new class of Navy ships.
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Velocity as vibration for measurand machinery condition analysis (A)

R. F. Misialek

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S9-S9 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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The paper presents the argument for using vibration velocity rather than acceleration or displacement as the measurand to more readily assess rotating machinery health and maintenance requirements. Also presented are the techniques used and the inherent advantages.
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Signal processing for a shipborne noise and vibration monitoring system (A)

D. W. Hackett and G. A. Hirschfield

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S9-S10 (1977); (2 pages)

Online Publication Date: 11 Aug 2005

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OTI has developed and is producing a shipboard signal processor for interfacing noise and vibration sensor signals with a digital computer and narrow‐band spectrum analyzer. The Monitoring System Signal Processor (MSSP) provides for 144 accelerometer and 6 hydrophone inputs, as well as A/D rand D/A conversions of auxiliary dc, ac, and discrete signals. The MSSP scans the input channels and conditions the incoming signals which are then fed through a bandpass filter and selector. The selected band is connected to a variable gain amplifier. The scaled analog data are low‐pass filtered, sampled, and converted to digital format. A block of 2048 digital samples are then stored and block transferred to the computer. The computer transfers the data to a separate spectrum analyzer for narrow‐band frequency conversion and ⅓ octave band generation. The computer provides for storage of threshold values for various ship speed ranges, and generates alarms and displays for operator action when these limits are exceeded. The system can be reconfigured to incorporate the frequency transform function into the MSSP. In conjunction with a small computer and suitable peripheral equipment this would comprise a compact NVM system for shipboard or industrial applications. [Work supported by NAVSEA and NAVSEC under Contract N00024‐75‐C‐7217.]
Contributed Papers
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Frequency, amplitude, and load effects on the dynamic properties of elastomers (A)

John E. Cole, III

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S10-S10 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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The dynamical‐mechanical properties of elastomer materials, which are widely used in devices such as antivibration mounts, are known to depend upon the nature of the loading of the material. While many aspects of the dependence of the dynamic properties on frequency and temperature are well known and customarily accounted for, these properties are also known to vary significantly with other aspects of the loading such as strain amplitude and static load. Furthermore, not all of these aspects of the loading appear to act independently. In this paper we discuss the dependence of the dynamic properties of elastomers on frequency, dynamic strain amplitude, and static loading. While the effects of frequency and strain amplitude appear to be separable, it does not appear to be as easy to deal with the effects of static loading. The implications of these effects on designs using elastomers is discussed. [Sponsored by USN Office of Naval Research—Structural Mechanics Program.]
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Improved lower bounds for fundamental frequencies of beams (A)

S. Hanna and C. D. Michalopoulos

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S10-S10 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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Lower bounds for buckling loads and fundamental frequencies of elastic bodies have been developed recently from energy considerations. In general, these bounds are very simple to calculate but they lack the accuracy of upper bounds. In this paper, an improved lower bound is obtained. Numerical results are presented to demonstrate the improvement on existing lower bounds. The method is specifically applied to determine a lower bound to the fundamental frequency of nonuniformly compressed beams. Comparison is made of these results with those obtained by other methods. [Work supported in part by NASA.]
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Dynamic stability of nonuniformly compressed beams (A)

S. Hanna and C. D. Michalopoulos

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S10-S10 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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The boundaries of the principal region of instability and upper bounds of natural frequencies of a nonuniformly compressed beam are determined approximately using the free‐vibration eigenfunctions of the uncompressed beam with the same boundary conditions. Specifically, beams under distributed compression, such as the beam's weight, and beams subjected to multiple concentrated loads are considered. Numerical results are given for beams having hinged‐hinged, fixed‐hinged, free‐free, and fixed‐free end conditions. [Work supported in part by NASA.]
back to top Session F. (Precis‐Poster Session) Underwater Acoustics I: Propagation, Noise and Sound Absorption
Precis‐Poster Papers
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Acoustics of an East Australian current anticyclonic eddy (A)

P. D. Scully‐Power, P. A. Nysen, and D. G. Browning

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S10-S10 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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The sound transmission characteristics of a typical eddy associated with the East Australian current during the Southern Hemisphere summer have been measured for the frequencies 25–2000 Hz. The dominant acoustic features of this warm core eddy were a 36‐m surface duct and a deeper 175‐m thick eddy duct. The eddy duct behaved as a classical acoustic wave guide with an optimum transmission frequency of 100 Hz. Strong acoustic coupling was observed between the ducts with rays up to 20 deg from the source in the surface duct being trapped in eddy duct. The coupling was independent of range and weakest for the frequency range 300–1000 Hz. Below 300 Hz coupling steadily increased due to diffracted energy. Above 1000 Hz coupling also increased due to scattered energy. [Work Partially Sponsored by Office of Naval Research.]
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Acoustic modeling of an oceanographic swirl (A)

D. G. Browning, J. J. Gallagher, G. E. Eubanks, and H. G. Schneider

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S10-S11 (1977); (2 pages)

Online Publication Date: 11 Aug 2005

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It has recently been found that eddy‐like oceanographic features can persist at certain locations due to bathymetric considerations. These features have been called swirls due to the nature of their circulation pattern. Various fixed and variable profile sound propagation prediction models were used to predict the effect of these swirls on sound propagation at frequencies between 50–15000 Hz. A typical case was 100 km in diameter and was fed by cold water current at the edge which spirals clockwise inward gradually heating to form a warm core. It was found that the most significant features were the temperature of the central core which depressed the depth of the main sound channel axis and the rate of cold water flow at the edge which determined the vertical width of a secondary sound channel which gradually diminished toward the center of the swirl. [Sponsored by Naval Underwater Systems Center.]
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General analysis of ocean eddy effects for sound transmission applications (A)

R. F. Henrick, W. L. Siegmann, and M. J. Jacobson

J. Acoust. Soc. Am. Volume 61, Issue S1, pp. S11-S11 (1977); (1 page)

Online Publication Date: 11 Aug 2005

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An analytical approach is used to obtain an approximate solution for deep‐ocean mesoscale eddies, including depth‐dependent effects. The solution is used in the development of an environmental‐acoustics model which relates acoustically relevant quantities, such as sound‐speed and current distributions, to eddy parameters. Parameters of the model are depth of influence, radius, rotational direction and maximum speed, and translational velocity. An application to a particular Gulf Stream ring is made, and the resulting current and soundspeed structures are shown to be in good agreement with observations. Then, general results are presented for rotational current structure, maximum horizontal sound‐speed change, and maximum SOFAR‐axis elevation as functions of eddy radius and peak current speed. It is shown explicitly how these quantities change significantly with eddy size and strength. This model provides a basis for subsequent analytical studies of sound transmission through an arbitrary eddy or eddy field. [Work supported by ONR.]
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