bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Characterization Method for the Numerical Evaluation of Level-Crossing Statistics for Impulsive Noise Processes
Authors: Lambert R. F. , Janssen R. A. , Dunens E. K.
Published: October 2005

In many impulsive noise problems, it is useful to be able to predict the level-crossing statistics of highly resonant systems. Formal analytical expressions can be obtained, but they are difficult to evaluate numerically. In particular, difficulties are encountered in the so-called small γ cases, where γ (the impulse-noise-density parameter) is defined as the product of the noise impulse-occurrence rate and the system response time. In order to obtain numerical results a two-step solution is proposed by first reducing the complex system to a simpler equivalent system whose level-crossing statistics are the same, and then the level-crossing statistics of the equivalent system are evaluated separately. Empirical observations indicate that the level-crossing curves of multimodal systems are similar in shape to those of a single-degree-of-freedom (1DOF) system; thus a 1DOF system is a likely equivalent system. The equivalent 1DOF parameters are determined by a power-weight method (PWM) of dynamic characterization whereby the equivalent bandwidth and equivalent center frequency are determined as the weighted average of the modal bandwidths and center frequencies with the modal powers as the weights. The second step, evaluation of the level-crossing statistics of a 1DOF system, has been done previously [R. A. Janssen and R. F. Lambert, J. Acoust. Soc. Amer. 41, 827–835 (1967)]. [Work supported by grant from the National Science Foundation.]
Effect of Silent Intervals on the Perception of Temporal Order for Vowels
Authors: Thomas Ian B. , Cetti Richard P. , Chase Paul W.
Published: October 2005

Experiments to determine the duration of four equal vowel segments necessary for correct perception of temporal order in a continuously repeated sequence of four vowel sounds were reported recently [I. B. Thomas et al., “Temporal Order in the Perception of Vowels,” J. Acoust. Soc. Amer. 48 (October 1970)]. In these earlier experiments each of the segments consisted entirely of vowel sound so that there were no silent intervals at all within a loop. In the present experiments, each of the four segments consisted of 50 msec of one of the vowels followed by a silent interval of variable duration. The vowels used were /i/, /ɛ/, /a/, /u/; total segments (vowel+silence) ranged in duration from 300- to 75 msec. Twenty subjects heard all stimuli binaurally in phase through headphones. They were required to state the order in which the vowel sounds occurred. For segment durations (T) of 100 msec or greater, order identification was near perfect; for T=87 msec score was 65%; for T=75 msec score was near chance (16.7%). A comparison of these results with those obtained in the earlier experiment shows that the silent interval facilitates order perception. [Work supported by NIH.]
Temporal-Order Perception of Vowel Sequences with Monaural and Binaural Presentation
Authors: Rupf John A. , Rowson Steve V.
Published: October 2005

The ability of subjects to repeat alternated speech depends on the alternation rate. The possibility that alternation interferes with the perception of temporal order was investigated in an experiment in which subjects determined the temporal order of vowel sequences under monaural and binaural conditions of presentation. Test stimuli were formed from segments of the vowels /i, ɛ, a, u/. Each stimulus consisted of four equal segments of the four vowels arranged in a random order. Segment duration was varied from 300 to 50 msec. For half the stimuli, the vowels were contiguous and presented to one ear, while for the remainder of the stimuli adjacent vowels were presented to opposite ears. On a given trial, using either the monaural mode or the binaural modes, the ability of subjects to determine the vowel order decreased monotonically with segment duration. Performance varied from near perfect with 300 msec segments to near chance with 50 msec segments. Performance with binaural stimuli was consistently lower than with monaural stimuli.
Relative Perceptual Cue Strength for Voiced Stop Consonants
Authors: Minifie Fred D. , Rudegair Robert , Milstein Roger , Vivion Michael
Published: October 2005

The relative strength of noise bursts and vocalic transitions as perception cues of word initial voiced stop consonants in CVC nonsense utterances was investigated using a tape splicing technique. All possible combinations of noise bursts and vocalic transitions in CVC utterances (using /b, d, g/ as initial consonants, /i, æ, a, u/ as vowel, and /z/ as the final consonant) were obtained by tape splicing-substitution techniques. Temporal segmentation was accomplished by inserting a piece of splicing tape before each utterance. A sonogram was made on which the location of the tape splice in relation to the utterance was shown. Measurement of the sonogram and conversion to distance along the tape allowed for a precise tape splice for substitutions of noise bursts and vocalic transitions (cue switching). The first 10 msec of noise burst and the following 50 msec vocalic transition were systematically substituted for presentation to a group of listeners. For example, each listener heard /biz/ produced in a normal manner, a silence inserted for the /b/ burst plus /iz/, and /b/ burst attached to all combinations of /iz/ which originally had been produced with either /d/ or /g/ as the initial consonant. Similiarly vocalic transitions were varied, so that each transition was substituted into all other CVC utterances. The results of this investigation indicate a slight preference for listeners to identify CVC syllables on the basis of the noise burst rather than on the basis of the transitional information.
Free and Prompted Recall of Connected Speech
Authors: Jarvella R. J.
Published: October 2005

Spoken connected discourse was interrupted for testing immediate recall at points where the speech just presented contained an identical sequence of words in one of two syntactic configurations. The clause unit previous to the one interrupted belonged in one condition to the immediate sentence, while in the other condition it was part of the previous sentence (e.g., “Before Donahue could finish, the members charged. Gaining access to the speaker's platform, they knocked down the local president twice.” vs. “Donahue was helpless to prevent members from gaining access to the speaker's platform. They knocked down the local president twice.”). Subjects were asked to listen normally to the speech and to write down as much as they could remember from just before the test pauses, or they were given the first word from the identical sequences as prompts (“gaining” in the example), and instructed to write down the speech from there up until the pauses. Results obtained from various verbatim measures of free and prompted recall support only the immediately heard clause and the immediate sentence as retrievable units in memory.
Study of the Perception of Pathologic Voices
Authors: Takahashi Hiroaki
Published: October 2005

A study was made of the perceptual dimensionality of hoarse voice in order to derive a limited number of perceptive criteria for classifying pathologic voices. Using 12 seven-point scales, eight listeners rated their auditory impressions of six recorded samples of the vowel [a] recorded from five patients with various kinds of laryngeal diseases and from one normal subject. The rating scores showed sufficient interlistener reliability. Four dominant dimensions were extracted from the data by D factorization. One of the four extracted dimensions was characterized mainly by evaluative scales, and this dimension appeared to be not as pertinent to the classification of quality of pathologic voice as it was to the distinction between normal and abnormal voice. The remaining three dimensions were considered to be relevant to the qualitative classification of pathologic voices. [This study was supported by USPHS grant.]
Characterization of Materials for Use in Surface Wave Applications
Authors: de Klerk J.
Published: October 2005

A theoretical method of determining the suitability of a material for use in elastic surface wave applications as well as the most suitable crystallographic directions for such uses will be described using the elastic, piezoelectric, and dielectric matrices of the crystal class to which the material belongs. The behavior of the more frequently used materials such as SiO3, LiNbO3, and Cds will be discussed. Directions of energy flow for different orientations in these materials will be derived.
A Review of Cavitation in Liquid Helium
Authors: Finch R. D.
Published: October 2005

Although the variety of possible cavitation nuclei in liquid helium is much restricted owing to its superfluid and thermal superconductive properties, it cavitates more readily than any other liquid. The threshold for ultrasonic cavitation in He II is lowered in the presence of quantized vortices induced either by rotation or alpha particle irradiation. Thermal superconductivity greatly influences the dynamics of incipient cavities and is believed to be responsible for the difference between the thresholds for audible and visible effects found to occur in He II. A theory proporting that bubbles evolve from molecular-sized holes by rectified heat transport will be advanced. According to this theory, the role of the quantized vortices in nucleation in He II is to provide thermal insulation for bubbles evolving in normal fluid at the vortex core. Further developments will be discussed in the light of this theory.
The Effect of Rotating Vanes on the Sound Field in Reverberation Chambers at Single Frequencies
Authors: Tichy Jiri
Published: October 2005

Results of the experimental investigation of the effect of rotating vanes on the sound field in reverberation chambers are presented. When the sound field is excited at single frequencies, the rotating vane splits the single-line spectrum into a multiple-line spectrum with the amplitude of the lines decreasing exponentially from the center frequency. Cumulative distributions of the sound pressure squared are presented and discussed at both the particular frequencies of the lines of the spectra and at the entire frequency band of the sound. The effect of the various shapes, positions, and speeds of the vane on the variance of the sound pressure squared, averaging: over different microphone travel paths, and autocorrelation relations of the sound field were also investigated. Practical conclusions for the sound power measurements in reverberation chambers are presented and discussed. The applicability of the existing formulas for the calculation of the variance of the sound pressure of the multitonal sound field was checked and the results discussed. Some results of the effect of the modal density on the various quantities mentioned are presented.
The Effect of Room Absorption on the Sound Power Output of the Ilg Reference Sound Source in a Reverberant Room
Authors: Ingalls Douglas J.
Published: October 2005

Previous work by others indicated differences in the sound power output of the Ilg depending upon the measurement techniques used. An experiment was performed in which the sound power output of the Ilg reference sound source (RSS) was determined from measurements of the space-time average of the pressure and the reverberation time as the room absorption was progressively increased by adding up to 14 panels (2ft×4ft×3 in.) of Owens Corning type 703 fiberglass. The results compared favorably with free-field measurements over a reflecting plane for low values of absorption and high frequencies but diverged for high values of absorption and low frequencies. Differences due to absorption were traced to using the Norris-Eyring equation for calculating absorption from the reverberation time. It is shown that use of a modified Sabine equation will yield the correct relationship between the absorption and reverberation time. Differences at low frequency disappear if the spatial pressure in the center of the room is corrected to the spatial pressure throughout the room as suggested by Waterhouse [J. Acoust. Soc. Amer. 27, 247 (1955)]. It is concluded that the sound power output of the RSS is independent of room absorption.
Transducer Design for a Sound Scattering Study
Authors: Hurwitz M. J. , Skinner D. D.
Published: October 2005

A set of transducers for studying the deep scattering layer has been designed. The transducers are designed to operate at 3, 12, 20, 40, 60, and 150 kHz. The four lower-frequency transducers were designed for this study and differ from conventional array design. The 3-kHz transducer is a combination of a piezoelectric ring transducer and a paraboloid reflector, designed to operate over the frequency range of 3–6 kHz. The transducer is constructed of staves of lead-zirconate-titanate circumferentially poled and mounted in a pressure equalized metal housing. The reflector consists of pressure-equalized air-filled compliant tubing made of thin-wall stainless-steel tubing, conformed to a paraboloid shape. Low side- and back-lobes resulted from this transducer. The 12-, 20-, and 40-kHz transducers are a combination of an acoustic lens and a tonpilz transducer. The lenses are planoconvex fluid-filled lenses about 4 wavelengths diam. The ontpilz transducers are contained in oil-filled pressure-equalized housings mounted at the foci of the lenses. The focal length is about 7/10 of the diameter. Beam patterns of the transducers are presented. The side lobes were reduced significantly by wooden baffles. Beam patterns with the baffles are presented.
Experimental Underwater Acoustic Imaging System
Authors: Knollman G. C. , Bellin J. L. S. , Brown A. E. , Weaver J.
Published: October 2005

A hydroacoustic imaging system is described which has been developed especially for close-range high-resolution (of the order of 1 mm) viewing in very turbid water. The system operates at nominal 2.5-MHz frequency and has a range up to 10 m in water of suspended ocean-sediment concentration as high as several thousand parts per million. Larger range capability is manifest for lower sediment concentration. Realtime kinescope displays are presented by the system of the acoustic field of view, which is that insonified by a high-intensity sound transmitter of total beamwidth variable up to 30° in 10° increments. Brief discussion is given of the sensitive (better than 10−10W/cm2) piezoelectric image converter which, with an accompanying mechanical scanning system, provides in effect a 10 000-element pickup matrix. Both a solid lens and a liquid lens are available; for focusing, the former lens is moved by remote-control drive, whereas the lens radii of curvature are varied hydraulically in the latter system. [Supported by the Naval Ship Systems Command.]
Reduction of Permanent Threshold Shifts through Intermittency (Chinchilla)
Authors: Ward W. Dixon , Nelson David A.
Published: October 2005

Two groups of four monaural chinchillas were exposed for 2 h to a 700–3000 Hz noise at 117 dB SPL. In one group the exposure was continuous; in the other, eight 15-min exposures were separated by 45 min of quiet. Both exposures produced initial CTSs so large as to be essentially unmeasurable. However, by 150-min post-exposure, the CTS had to be dropped to about 70 dB for the intermittent group, but was still 100 dB for the continuous group. Finally, although the intermittent group showed full audiometric recovery two weeks after exposure, the continuous group had 40 dB of PTS after three months. Clearly, damage-risk criteria that ignore the temporal pattern of the noise exposure (such as the present proposal before the International Standards Organization) are grossly incorrect, just as one would infer from TTS-alone studies on humans and from the relatively low actual incidence of hearing losses among workers in which exposures to high levels are intermittent, such as in miners, foresters, and rock musicians. [Supported by the National Institutes of Health, Public Health Service, and Department of Health, Education, and Welfare.]
Temporary Threshold Shifts Produced by Prolonged Exposure to High-Frequency Noise
Authors: Mills John H.
Published: October 2005

Four trained chinchillas were exposed for 24 days to an octave-band noise centered at 4 kHz. The SPL of the noise was 57 dB for days 1–6; 65 dB for days 7–12; 72 dB for days 13–18; and 80 dB for days 19–24. The results are similar to those described previously by Carder and Miller for a low-frequency noise: (1) TTS reaches an asymptote in about 24 h; (2) in the region of maximum TTS, the relation between TTS at asymptote and the level of the noise is given by the equation TTS = 1.55 (SPL-A), where A is about 45 for the high-frequency noise and about 64 for the low-frequency noise. This 19 dB may be accountable in terms of the acoustics of the chinchillas' external and inner ears. In a second experiment, four trained chinchillas were exposed for 24 days to the same noise. The SPL was 57 dB for days 1–3; 72 dB for days 4–6; and 57 dB for days 7–27. The major finding is that when the level of noise is reduced from 72 to 57 dB, recovery to the asymptote predicted for the 57-dB exposure required 16 days.
Acoustic Behavior of Three Sympatric Species of 17-Yr Cicadas
Authors: Simmons J. A. , Wever E. G. , Strother W. F. , Pylka J. M. , Long G. R.
Published: October 2005

Adults of three species of the 17-yr cicada, Magicicada septendecim, M. cassini, and M. septendecula, emerge from the ground together over a three-week period to mate and lay eggs. The males produce sounds (bursts of 1.0–1.5 kHz for septendecim and 4.0–6.0 kHz for cassini and septendecula) when congregating and when disturbed. Neural responses from within the chitinous capsule of the auditory receptors showed greatest sensitivity between 1.0 and 3.0 kHz in male and female septendedim and between 3.5 and 7.0 kHz in both sexes of cassini and septendecula. The tympanic membrances of the males are partially collapsed by muscles which contract during sound emission, reducing auditory sensitivity by 5–15 dB. Behavioral audiograms of males indicate best hearing in septendecim at 1.2–1.8 kHz and 4.5–6.0 kHz in cassini. Each species is very insensitive to frequencies used by the other. The sound level (80–95 dB SPL) around infested trees probably discouraged predation by driving away birds.
Development of a Dictionary for Speech Synthesis
Authors: Allen J.
Published: October 2005

In order to synthesize any given English text, it is necessary to convert the text to a phonemic representation. In the procedure discribed, function words, prefixes, suffixes, “functional roots” (as “pel” in “impel, propel, repel”), and exceptions form a base dictionary. A large corpus of words is then processed, shortest words first, by attempting to decompose each word into prefixes, roots, and suffixes which are in the base lexicon. If the decomposition fails, or is judged to be incorrect, then the word may be added to the lexicon. There is a tendency, however, for the short high-frequency words of English to be more irregular from the letter-to-sound point of view than words of lower frequency. Hence content words are examined for possible conversion directly by a letter (s)-to-sound algorithm. In this way, the conversion of text to phonemes uses a dictionary that takes advantage of the morphemic structure of English words, and yet does not include those words that can be converted directly without the need for lexical entries.
Computer Application to Dynamic Palatography
Authors: Paterson Robert L. , Proffit William R. , McGlone Robert E.
Published: October 2005

This paper describes the use of a time-shared IBM 1800 system to obtain dynamic palatographic information during speech. Linguopalatal contact was recorded by miniature pressure transducers embedded in a thin appliance that covers the maxilla. These transducers are positioned around the alveolar ridge from left to right molar. Analog pressure signal processing by the computer permits the collection of considerable data for each subject and also the study of many more subjects. The basic operation is divided into acquisition and recovery. The signals are simultaneously recorded graphically and stored in the buffer memory. If the analog signals are satisfactory, they are saved; if not, the stimulus is again presented. Each speech item is automatically identified for the computer as the subject stimulus is generated. Recovery consists of same-day subject data and long-term group data. Peak pressures, integrated pressure-time values, and time sequences between transducer contacts and the acoustic signal are recorded. Examples of speech and swallow patterns will be presented.
Influence of Center Frequency on Preference Evaluation of Bandpass Filtered Speech
Authors: Sessler G. M. , West J. E.
Published: October 2005

The subjective influence of the center frequency of bandpass filtered speech samples on preference was investigated. Test stimuli were derived from a single speech sample (male voice). The signal bandwidth was varied utilizing all possible combinations of the lower cutoff frequencies 250, 350, 500 Hz, and the upper cutoff frequencies 3, 4.2, and 6 kHz. The signal was also reverberated with reverberation times of 0.1, 0.2, and 0.3 sec. Listening experiments were conducted with 11 subjects employing a forced-choice paired-comparison method [G. M. Sessler and J. E. West, Proc. Int. Congr. Acoust., 6th, 1968, Paper C-5-8]. A factor analytic technique was used for analyzing the data. It was found that for constant bandwidth (in octaves) and constant reverberation time, the subjective preference was higher for stimuli with low center frequency. For example, stimuli filtered with a 250-Hz to 3-kHz bandpass (bandwith 2.75 kHz) are generally preferred to stimuli with equal reverberation time filtered with a 500-Hz to 6-kHz bandpass (bandwidth 5.5 kHz). The present study thus indicates that, within the above limits, use of low center frequencies results in higher preference and a substantial reduction in absolute bandwidth.
Contextual Relativity of Speech Recognition Cues
Authors: Schultz M. C.
Published: October 2005

The use of distinctive features as cues to speech recognition should result in performances for signals that differ as a function of response alternatives. Recognition of a speech unit that shares many features of alternative responses must rely upon reception of the one or few uniquely held features. Recognition of a speech unit that shares few, if any, features will occur with reception of (almost) any of its features. A four-person talker-listener round robin generated nonsense syllables of a CV type using the consonant /t/ and two others, and the vowel /a/ and two others. Each of the nine syllables was delivered 100 times in random order in each set. Each listener responded with a choice for each signal plus a confidence rating on his decision. Additional sets were generated by retaining the consonants and the /a/ but using two different vowels, or by retaining the vowels and /t/ and using two different consonants. Other sets used the original elements but always placed an /r/ for a CrV syllable, and still others added a final /k/ for a CrVk syllable. Utilities of response choices were systematically varied and response confusions generated for each talker-listener dyad. Results on stability of recognition performance pertinent to the influence of context are discussed.
There's Many a Slip Twixt the Brain and the Lip
Authors: Fromkin Victoria A.
Published: October 2005

The difficulties inherent in modeling a speech-production system stem from its great complexities and from the fact that the only direct information available to us concerns the output characteristics of the system. Thus, the input units and the properties of the mechanism itself must be inferred primarily from output data. An analysis of over 700 speech errors reveals that these data are an invaluable source of information regarding both the units processed and the sequencing of events in the production of an utterance. The kinds of errors which occur show that, whereas the articulators move in an analog fashion producing a semicontinuous acoustic signal, discrete units, similar to the abstract units posited by linguists, underlie the speech-production process. Distinctive features, segments, syllables, lexical and grammatical morphemes, and “labeled” syntactic phases must all be posited as performance units to account for the errors which occur. Furthermore, there are language-specific rules, analogous to grammatical rules, which constrain the production process. These rules must be strictly sequenced in the model to insure valid predictions. Evidence is presented in this paper for the reality of certain highly abstract representations of formatives which are actualized phonetically only in speech errors, and for specific morphophonemic rules which must be ordered before phonological-phonetic rules. A sequential ordering of events in the generation of an utterance is proposed.
A Distinctive Feature Analysis of Misarticulated Consonants of Speech-Defective Children and Adults
Authors: Asp C. W. , Williams M. L.
Published: October 2005

Data on consonant misarticulations were obtained from the clinical records of 1373 subjects who were diagnosed as functional articulation cases at the University of Tennessee Hearing and Speech Center over a 12-yr period. Twenty-two consonants were tested in the initial position, 24 in the medial, and 21 in the final position. These data were analyzed by an IBM 7040 computer to tabulate the frequency of the errors and to compute chi-square values and Spearman Rank Order Correlations. Singh's (1968) distinctive feature system was utilized for the distinctive feature classification. The results indicated that the frequency of the substitutions usually decreased as the number of distinctive feature differences increased. When the number of distinctive feature differences was identical, the errors did not occur with equal frequency. Alveolar consonants were the most frequent substitutions. Friction plus and nasality plus “improved” with age. The rank order of the correct use of the features was voicing, nasality, friction, duration, glide, and liquid. Distinctive feature “rules” may be useful as clinical guidelines for diagnosis, prognosis, and therapy of misarticulations.
Perception of Stop Consonants and Vowels in Temporally Staggered Dichotic CV Syllables
Authors: Kirstein Emily
Published: October 2005

Dichotic stop-vowel syllables differing only in the stop are more accurately recalled from the right ear than the left. When the onset of one syllable is delayed by 20–120 msec, the delayed stop is more accurately identified than the leading one. Neither the ear advantage nor the lag advantage occurs reliably with dichotic steady-state vowels. The present research investigated the perception of vowels and stops in CV syllables differing between ears in both vowel and consonant. Delays between ears were 0, 50, or 70 msec. In any session, subjects identified only vowels or only consonants. They also judged which was the clearer stimulus on each trial. Although listeners usually identified both stimuli correctly on each trial, they judged vowels as well as consonants as clearer when they lagged or were at the right ear. Thus, when both vowels and consonants differ between ears, lag effects and laterality effects are maintained for consonants and are induced for vowels. Mode of perception—speech versus nonspeech—appears more important than acoustic factors to account for the previously reported differences between dichotic vowels and stops. [Supported in part by a grant to Haskins Laboratories from NICHD.]
Intelligibility Cues in Normal and Distorted Speech Forms
Authors: Stewart J. L.
Published: October 2005

Normal and distorted but high-intelligibility speech forms are compared using a millisecond-resolution analog ear display. Pattern details which convey intelligibility are identified separately from those which relate to matters of quality. Distorted speech forms include high-pass filtered normal speech, whispered speech, whistled speech, helium speech, and infinitely clipped speech. The concept of a single principal formant is partly justified. In addition, there exist brief periods when activity penetrates into the ear further than the position of the formant, these events being periodic or random for voiced or whispered sounds, respectively.
Sequential Testing of Speech Discrimination
Authors: Bode D. L. , Carhart R.
Published: October 2005

Levitt and Rabiner recently described the use of sequential strategies for the measurement of speech intelligibility [J. Acoust. Soc. Amer. 42, 609–612 (1967)]. We employed the best-of-five strategy to measure the S/N ratios required for 30%, 50%, and 70% discrimination of CNC words in white noise. Twelve normal hearers listened monaurally during test-retest sessions to Northwestern University Auditory Test No. 6. The stimulus level was varied depending on subject performance on successive blocks of five words or less. The resulting discrimination functions were generally in close agreement with findings obtained by other investigators who used conventional test procedures. Test-retest effects showed approximately 2, 1.5, and 1 dB improvement in S/N ratio at 30%, 50%, and 70% target discrimination, respectively. Speech reception threshold (SRT) in noise with spondee material also was measured. Mean SRT-in-noise scores closely approximated the S/N ratios at which 30% discrimination was obtained. Estimating discrimination functions on the basis of the S/N ratios yielding SRT and 70% CNC discrimination gave reasonably accurate replications of the measured functions. [Research supported by National Institute of Neurological Diseases and Stroke.]
Effects of Oral-Muzzle Pressure upon Underwater Speech Intelligibility
Authors: Coleman Robert F. , Krasik Wilma
Published: October 2005

The design of most SCUBA communication equipment requires that the diver/talker speak into a slightly raised air pressure to prevent back flooding at the exhaust port of the system. This study sought to determine the effect on intelligibility of speaking into such an elevated pressure. Three male and two female speakers read standard intelligibility word lists as they wore an oral muzzle adjusted to exhaust release at 0, 1, 2, 4, and 6 cm/H2O re atmospheric pressure. Each talker also read one list into the same microphone and recording system without the constraints of the oral muzzle. Recorded stimuli were played to 20 listeners who identified each word as one of five choices in a closed response set. Results indicated a systematic trend for intelligibility scores to decrease with increases in muzzle release pressures. The effect of donning the oral muzzle itself was to decrease intelligibility by 20%, while scores over all pressures ranged from 14% to 20% for individual talkers. Phoneme substitution error analyses were also determined.
Measurement of Spectrum Levels for Shallow Explosive Sources
Authors: Parkins B. E. , Worley R. D.
Published: October 2005

The measurement of transmission loss in the ocean using explosive sources requires knowledge of the spectrum level of the energy released in a given frequency band as it would be measured as in a boundary-free medium. For the case of shallow charges the measurement of these spectrum levels is often complicated by the fact that the refracted and surface-reflected arrivals, each containing an initial impulse followed by a series of bubble pulses, cannot be separated by the usual technique of receiver gating. In recent measurements of the spectrum level of 1.8-lb charges detonated at 60 ft, this difficulty has been obviated by separation of the two arrivals in the frequency domain rather than in the time domain. This was done by smoothing the spectrum of the recorded waveform to reduce the wide variation caused by oscillations of the gas bubble and then adjusting the smoothed spectrum by the amounts necessary to account for the Lloyd's Mirror interaction. The results obtained in this way agree well with values for deeper explosions reported by Christian [E. A. Christian, J. Acoust. Soc. Amer. 42, 905–907 (1967)] at the upper end of the spectrum where the levels are nearly depth independent. [Work supported by the U. S. Navy Electronic Systems Command.]
The Propagation of Sound in a Wedge-Shaped Shallow-Water Duct
Authors: Bradley D. L. , Hudimac A. A.
Published: October 2005

The acoustic field in a wedge-shaped shallow-water duct is described. Beginning with the inhomogeneous Helmholtz equation, integral transform techniques are used to obtain the field of a point source (the Green's function) extended Riemann surface. Image theory is applied to obtain the generalized geometric acoustic solution in a bounded medium, which is a sum of these point sources. The behavior in a wedge-shaped duct and in a duct with parallel boundaries is compared. The geometric acoustic solutions are then transformed to normal-mode or wave-acoustic solutions. Calculation of the normal-mode field of the wedge requires evaluation of an integral appearing in the solution by the method of steepest descents or saddle-point integration. Further comparison is then made between the normal-mode acoustic fields of the parallel duct and of the wedge-shaped duct.
Statistical Analysis of Reverberation Data Obtained from the Surface of a Fresh Water Lake
Authors: Plemons T. D. , Shooter J. A. , Middleton D.
Published: October 2005

A statistical analysis using ensemble averaging was made of reverberation data obtained from a wind-driven fresh water lake surface. A gated pulse was used to insonify the lake surface to produce the reverberation data. FM and CW signals having a center frequency of 110 kHz and varying pulse lengths were transmitted. The Kolmogorov-Smirnoff test was applied to the data to determine homogeneity. If the data proved to be homogeneous, then second-order statistics and some first-order probability density functions were estimated. In particular, the ensemble covariance was measured and from this the intensity spectrum was calculated. Each of these quantities was compared to theoretical predictions. The first-order distributions of the amplitude and envelope are shown to be Gaussian and Rayleigh distributions, respectively. Some data proved to be inhomogeneous and possible physical reasons for the inhomogeneity are discussed. [This work was performed under contract with Naval Ship Systems Command.]
Correlation Coefficients for Sound Propagation through a Random Medium
Authors: Hadden W. James
Published: October 2005

Two-point correlation coefficients are presented for the fluctuations in the time-averaged amplitudes of pulses, with angular frequency, propagated from a point source through a medium whose index of refraction varies randomly about the average value, unity. The fundamental analysis has been set forth by Mintzer and Hadden [“Two-Point Correlations for Random-Medium Acoustic Propagation,” in In Honor of Philip M. Morse (MIT Press, Cambridge, 1969), pp. 106–115]. It is assumed that the autocorrelation function for the index-of-refraction fluctuations has a Gaussian form. Results are presented for arbitrarily oriented observation points in the farfield of the source for two types of refractive index autocorrelation functions: (a) spherical—with the same correlation length in all directions; (b) spheroidal—e.g., with one correlation length in the horizontal plane and a different correlation length in the vertical direction.
Reflection of a Sound Ray Bundle from a Sloping Ocean Bottom
Authors: Proni J. R.
Published: October 2005

The theory for calculating the intensity of sound in a refracting medium after reflection from a sloping bottom was first formulated by Einstein and Eby [L. T. Einstein and E. S. Eby, USL Tech. Memo. No. 1210-103-60 (1960)]. However, they did not pursue their development to the point of evaluating certain angle derivatives which are necessary to obtain quantitative results. The present paper describes such a computation for the particular case of up- and down-slope reflection from a flat inclined bottom bounding a medium in which the sound speed gradient is constant. The results have an important bearing on the sound intensities obtained with most ray tracing programs, since these usually trace rays from receiver to source, and a correction must be applied to obtain the intensity for the reverse path. For the flat bottom or for RSR or refracted transmission, this correction factor is the well-known ratio Cs2/Cr2, where Cs and Cr are the sound speeds at the source and receiver, respectively. This factor is not modified in the presence of reflection from a sloping bottom. [This work was supported by the U. S. Navy Electronic Systems Command.]
A Ray-Theoretic Perturbation Solution for Propagation in Inhomogeneous Fluids
Authors: Hudimac A. A.
Published: October 2005

The conventional ray-theory solution of the Helmholtz equation with a nonconstant wavenumber is the exact solution of an auxiliary equation. The exact field is obtained in terms of a perturbation of the wavefield which satisfies an inhomogeneous form of the original Helmholtz equation. The Green's function for this is obtained in terms of the ray-theory solution and a perturbation. The process is repeated leading to a succession of multiple integral terms with each term having one more space integral than the previous one. The same results are obtained by an integral equation approach. Some attempts at specifying sufficient conditions for convergence will be discussed.
Precise Measurements of Mean Horizontal Sound Velocities
Authors: Jaques A. T. , Kelley C. E.
Published: October 2005

Mean horizontal velocities of sound propagation in the ocean, defined as the ratio of the horizontal range to the one-way travel time, have been measured. Single-dimension RAYDIST equipment is used to measure the horizontal distance between source and receiver, and a radio link is used to determine the one-way travel time. Measured mean horizontal velocities are compared with values computed by ray-tracing methods for which the sound-velocity profile is obtained from in situ bathythermograms. Comparisons of mean horizontal velocities are presented out to ranges of 15 miles for combinations of source and receiver in and below the surface duct.
Sound Propagation Studies of some Implosive Sources
Authors: Vent R. J. , Northrop J. , Morrison M. F.
Published: October 2005

A series of about 40 small (2-in. diam) inexpensive (approximately $70 per thousand) plastic spheres were sunk and thus imploded at sea near Westfall Seamount (30.5° N, 120.5° W). The implosive signals were monitored on both shallow (50-ft) and deep (1100-ft) hydrophones, suspended from the ship. Three types of spheres were tested and found to implode at 1800-, 2350-, and 2680-ft depths, respectively. Sink rates of 225–300 ft/min. were achieved using sections of pipe, or other hardware, as sinkers. Energy per unit area spectrum levels in the 0.5- to 5-kHz frequency band were, for one type of hydrosphere having an average implosion depth of 2680 ft, comparable to those for a 0.002-lb detonator (TNT). Use of such safe, inexpensive, and reliable implosive devices is recommended for acoustic work at sea when short pulses of relatively low signal strength are required.
Measured Dependence between Time and Frequency Spreading of One-Way Underwater Sound Propagation and Sea Surface Motion
Authors: Moldon J. C.
Published: October 2005

The randomly time-varying multipath introduced by scattering from the sea surface is often the dominant cause of time and frequency spreading of underwater sound propagation. Measurements are presented of such acoustic dispersion together with corresponding surface-wave statistics for transmitter frequencies of 4.7 and 9.4 kHz with grazing angles of 5° to 30° and Sea States 1 to 3. Time spreading of short pulse signals is compared with wave slope distributions that were obtained from surface glitter photographed at night with an airborne camera and flasher. Frequency spreading measurements are compared with surface motion recorded by a wavepole. Good agreement was found, particularly at higher grazing angles, for a simple model in which Doppler spread is proportional to sine of the grazing angle and standard deviation of the vertical velocity component of the surface motion.
Surface Reverberation by Oil-Polluted Oceans
Authors: Hayre H. S.
Published: October 2005

The surface reverberation from open-ocean surface polluted with either fresh oil films or a random oil globule layer near the top air interface poses a unique problem in underwater studies since a larger and larger portion of the high seas are progressively becoming polluted in this manner. Of course, the otherwise random water interface and the water motion underneath it cause sufficient complications. This paper describes some laboratory simulated data on such reverberation as well as projected theory to account for this oil pollution. The results show that there is significant reduction in signal strength due to the surface pollution at near vertical incidence, whereas the signal strength near grazing angle almost bears no relationship to that from the otherwise normal water/air interface. The paper further speculates on the effect of such a practical situation on operational capabilities of underwater systems.
Reflection Coefficient at a Fluid-Solid Interface
Authors: Mott G.
Published: October 2005

A sharp minimum in the reflection coefficient at a fluid-solid interface has been associated with surface wave generation. At this minimum, an unusual lateral displacement of the reflected beam occurs. These facts are expected to permit highly accurate measurements of certain groupings of the elastic constants of the two media.
The Velocity Dispersion of Rayleigh Waves Propagating along Rough Surfaces
Authors: Sinclair Rex
Published: October 2005

The frequency dependence of the velocity of Rayleigh waves propagating along rough surfaces is examined from the viewpoint of the mass loading of a smooth surface. Graphs of predicted values are given for examples of idealized surfaces on a solid of Poisson's ratio 0.3.
Forced Vibration of Internally Damped Circular and Annular Plates with Clamped Boundaries
Authors: Snowdon J. C.
Published: October 2005

Closed-form expressions have been derived for the driving-point impedance, transfer impedance, and force transmissibility of circular and annular plates with clamped boundaries. The plates are internally damped and are driven either by a sinusoidally varying central point force or by one or more concentric ring forces of variable radii. The circular plates are mass loaded or elastically restrained at their midpoints, or are loaded by an ideally rigid annular mass (rib) of arbitrary radius. Computed results illustrating the frequency dependence of impedance and transmissibility are described, and their physical significance is discussed. Added mass is very effective in increasing plate impedance levels and in blocking force transmission to the plate boundaries, particularly when it is positioned directly beneath the driving force. [Supported jointly by the U. S. Naval Ordnance Systems Command, the U. S. Naval Ship Systems Command, and the U. S. Office of Naval Research.]
Effects of Sonation an Vacuolate Plant Cells
Authors: Gershoy A.
Published: October 2005

Cinemicrophotography has been used to study deformations and motions produced in squash “hair” cells by ultrasound. Typically, part of a cell wall, say, at P is set into vibration at 85 kHz with the tip (about 20 μ in diam) of a Mason horn. At peak-to-peak amplitudes of the order of 0.1 μ viscoelastic reversible displacements of cytoplasmic particles and membranes are seen near P. The amplitude threshold for these reversible effects depends on effectiveness of the sonic “contact” at P and also on the sonication time. At higher amplitudes, fragments of the parietal cytoplasm near P are separated from the surrounding cytoplasm and ejected into the vacuolar water. These remain isolated thereafter and lose internal structure. After sonication of a few seconds resulting in moderate tearing, the cell usually recovers; there ensues a rapid reconstruction of a pattern of radially oriented channels. However, if sonication is continued for long periods even without visible effects, the cell may die. Some of the observations can be accounted for in terms of second-order acoustical theory, others in terms of biological responses. A film will be shown. [Supported in part by an NIH grant.]
Ultrasound Visualization of Excised Breast Tissue: An Experimental Approach to the Problem of Precise Identification of Structure from Echogram Data
Authors: Fry Elizabeth Kelly , Franklin T. A. , Gallager H. Stephen
Published: October 2005

The characterization of the female breast by ultrasonic visualization techniques presents unique problems in comparison to visualization of other body areas. Basic to this uniqueness is the fact that, not only does the breast contain a variety of types of tissues, but the amount of each type of tissue is a variable. Correct identification, from the echogram presentation, of abnormalities located within any of these tissue structures is partly dependent on the ability to correctly identify normal echogram patterns over the full range of this variability; such identification necessitates precise correlation of the normal echogram pattern with the specific tissues and with their orientation in the path of the sound beam. However, this type of correlation is difficult to obtain in the in vivo breast. This paper discusses possible source of errors in such attempts. The basic data required to prevent such errors of interpretation of breast echograms can be obtained by carrying out a detailed acoustic visualization study of excised whole breast tissue, followed by correlation of the echogram patterns with the gross and histological sections of the breast tissue. Data obtained to date, using this approach for both normal excised breast tissue and excised tissue containing malignant abnormalities, will be presented.
An Intensity Differential Equation in Ray Acoustics
Authors: Solomon L. P. , Armijo L.
Published: October 2005

The desired ultimate output of either ray acoustics or normal-mode analysis in underwater sound-propagation problems is the prediction of the intensity at some field point. In ray acoustics, a technique has been the ray-bundle approach. By formulating the ray-path problem in terms of a differential equation rather than in terms of a range integral, a second differential equation can be obtained which describes the continuous variation of intensity along the ray. An extension of the calculation of intensity to allow for variation of the speed of sound with range as well as depth is easily accomplished. It is shown that, for the intensity function to be continuous, a sufficient condition on the velocity function is that it be twice continuously differentiable.
Modified Ray Theory in the Presence of a Boundary
Authors: Davis J. A. , Murphy E. L.
Published: October 2005

The modified ray theory based on generalized WKB solutions to a two-turning-point problem for an unbounded medium having a maximum in sound velocity [E. L. Murphy, J. Acoust. Soc. Amer. 47, 899–908 (1970)] has been extended to include a pressure release surface and a rigid boundary at the maximum. This modified ray theory, unlike ordinary ray theory, predicts a frequency-dependent phase change which varies continuously for the transition from normal incidence rays to rays which reverse far from the boundary. The behavior of this phase, and in turn its derivative, gives rise to a frequency-dependent beam displacement for ray bundles. The results have the same form as for the unbounded problem but with an additional important contribution. These beam-displacement phenomena can have the consequence of introducing caustics or convergence zones where none exist according to ordinary ray representations and distorting caustics and shadow zones in a frequency-dependent way when they do exist in the ordinary ray picture. Results of analyses for simple velocity profiles characteristic of the ocean indicate that these frequency-dependent diffraction effects can be significant for frequencies on the order of 50 Hz.