bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial and temporal fluctuations using the parabolic profile
Authors: Ramsdale D. J.
Published: October 2005

Calculations have been performed using the normal-mode solutions to the parabolic sound-speed profile to estimate the fluctuations in a low-frequency CW acoustic signal transmitted over large distances in the deep ocean. Temporal fluctuations are estimated by fixing the source and receiver and allowing the profile to vary in such a manner as to approximate the effect of the first mode 12.42-h internal tide propagating in a direction perpendicular to the source/receiver line. Spatial fluctuations are estimated by allowing the source to move at constant speed through a frozen ocean at approximately the same range as that used for temporal fluctuations. Preliminary results indicate that although both spatial and temporal fluctuations may be of approximately the same magnitude, the spatial fluctuations even at a moderate source speed of 7 knots occur at a much more rapid rate than do the temporal fluctuations.
Long-range, low-frequency acoustic amplitude and phase fluctuations at two frequencies
Authors: Spindel R. C. , Porter R. P.
Published: October 2005

Fluctuations of underwater sound at two transmission frequencies an octave apart (220 and 406 Hz) have been observed simultaneously for periods up to eight hours. Transmission was from moored sources to free-drifting hydrophones 260 km distant. The drifting receivers were tracked to within a fraction of a wavelength of the transmission frequency. In this way, synthetic spatial apertures up to 8 km in length were created. The 220- and 406-Hz phase variations are highly correlated for periods greater than about 1 h. For shorter periods there is a decline in correlation attributed to the slightly different paths traversed by the two transmissions due to a 4-km spacing between sources. The magnitude of the phase fluctuations at 406 Hz was twice that at 220 Hz over the experimental limits of 0.225 to 30 cycles/h. The phase-fluctuation power spectrum does not cut off the local buoyancy frequency in keeping with previous observations, but in disagreement with internal-wave models of acoustic fluctuation. The amplitude-fluctuation spectrum level constantly decreases with increasing frequency in contrast with data taken over longer ranges (1400 km), which is generally fiat to about 4 cycles/h and then falls off abruptly. Correlation times of the data are discussed.
Chemical aspects of optoacoustic spectroscopy
Authors: Robin M. B.
Published: October 2005

Molecular spectroscopists have studied the absorption of optical radiation for over 100 years, but only in the last five years have experiments come forth on the subsequent relaxation of the molecular excitation to produce heat. By detecting this heat as an acoustic pulse using sensitive microphones and bolometers, the eventual fate of absorbed photons can be followed, both energetically and kinetically. Several examples of the unique information derived from this acoustic method of molecular spectroscopy will be presented.
Theory of the photoacoustic effect with solids
Authors: Rosencwaig Allan , Gersho Allen
Published: October 2005

Chopped light impinging on a solid sample in an enclosed cell produces an acoustic signal within the cell, A theoretical explanation for this effect is presented, providing a quantitative foundation for photoacoustic spectroscopy. Nonradiative de-excitation of the absorbed light within the solid sample produces a periodically varying heat flow from the sample to the surrounding gas and backing material. The solution to the thermal diffusion equations shows that only a thin boundary layer of gas adjacent to the surface of the sample responds thermally to this periodic heat flow. The boundary layer can then be thought of as acting as an acoustic piston creating the acoustic signal detected in the cell. An explicit formula gives the. magnitude and phase of the acoustic pressure in terms of the optical, thermal, and geometric parameters of the system. Simple approximations for the pressure are given according to the relative magnitudes of the optical absorption length, thermal diffusion length, and thickness of the sample. The results imply, in particular, that absorption data may be obtained by photoacoustic spectroscopy, even from samples that are completely opaque to conventional techniques.
Partial imaging of sound fields
Authors: Clark J. A.
Published: October 2005

Partial images of sound fields are obtained by illuminating acoustic tonebursts with short pulses of coherent light. The acoustically modulated light produces a diffraction pattern at the focus of a condensing lens. All but selected portions of the diffraction pattern are spatially filtered out of the light beam. The region of the sound field is then photographed with the beam of spatially filtered light. Two new acoustooptic effects have been observed by this method of partial imaging. One effect is a set of different acousto-optic grating images associated with the same sound field, which are obtained by filtering out but selected combinations of diffraction orders. The second effect is a set of amplitude-dependent acousto-optic fringes which can be observed in the partial images of sound fields where only a single diffraction order is permitted to pass through the spatial filter. The two effects appear to have significant potential as a means for obtaining whole-field optical measurements of the phase and amplitude of arbitrary sound fields.
Signal detectability as a function of interaural signal-frequency disparity and signal duration
Authors: Grantham D. Wesley , Karpicke John A. , Robinson Donald E.
Published: October 2005

The relationship between interaural signal-frequency disparity (Δf) and signal duration (t) was investigated using a two-alternative temporal forced-choice procedure. The signals consisted of a tone (400 Hz) in one ear and a tone of a different frequency (400 + Δf Hz) in the other ear, where Δf = 4, 8, or 16 Hz. As a reference condition a diotic signal (Δf = 0 Hz) was also employed. Signal duration was either 256, 512, 1024, or 2048 msec. All signals were presented in a background of wide-band, diotic Gaussian noise. In the diotic condition performance improved as t increased. In the dichotic conditions, for a constant signal duration, performance deteriorated (average of 1 dB) as Δf increased; for a constant Δf, performance improved (average of 2.5 dB) as t increased. The results are discussed in terms of the number of alternating diotic (SO) and phase-reversed (Sπ) “looks” available in a signal interval.
Lateralization of partials of complex tones with pure tones
Authors: Deutsch Werner A.
Published: October 2005

The ability to detect lateralization images of individual partials of harmonic tone complexes with pure tones was measured in a yes/no task. It is supposed that partials of complex tones build up lateralization images with pure tones of equal frequency and amplitude. It has been found that the upper limit of lateralization produced by introducing interaural time differences is slightly reduced from that in pure-tone-pure-tone cases. No difference in correlation has been found between lateralization obtained with partials resolved or unresolved by the ear or with those partials covering the “dominance region.” The results are in good agreement with data reporting of fusion at higher frequencies between dichotically presented signals with gross interaural frequency differences. [This work was supported by the AKG, Vienna, Austria.]
Binaural intensity JNDs for transients
Authors: Hafter E. , Aronow H. , Dye R. , Nuetzel J.
Published: October 2005

Difference thresholds for interaural intensity (ΔI) were measured as a function of overall interaural intensity disparity (I) using a same-different lateralization paradigm. The signals tested were high (3–4 kHz) or low (0.1–2 kHz) frequency bandpass clicks. Values of I ranged from 0 to 32 dB, while the average overall level for each binaural click was maintained at 48 dB SPL by symmetrically dividing the values of I and ΔI between the two ears. Controls were included to account for information contained in monaural loudness increments, and differences between binaural and monaural thresholds were taken as measures of subjects' intensity-based lateralization abilities. Hafter and DeMaio [J. Acoust. Soc. Am. 57, 181–186 (1975)], also using clicks, reported that sensitivity to interaural time (Δt) falls off gradually as the overall difference (t) increases. Within the framework of a model which equates intensity differences to time differences, use of these earlier data may permit extraction of “true” intensity-based lateralization, independent of both monaural and temporal cues. Our results verify that, at least for the high-frequency range, such interaural intensity differences are indeed useable cues for lateralization. Acuity for the interaural intensity cue declines slowly for images lateralized away from the midline; use of the cue deteriorates completely as I reaches values near 24 dB. [Supported in part by grants from the NIH and HIMH.]
Determination of masking-level differences in a reverberant environment
Authors: Koenig A. H. , Allen J. B. , Berkley D. A. , Curtis T. H.
Published: October 2005

A masking-level difference paradigm was used to measure release from masking in a reverberant environment. Microphones were placed in the ears of a mannequin which was situated in a reverberant chamber. A single white-noise source was fed into loudspeaker also situated in the chamber with the loudspeaker facing one corner of the chamber to minimize the direct sound reaching the mannequin. The output of each microphone served as the masker, while the signal (250-Hz pulsed tone or speech) was electrically inserted at the subject's earphones. For the diotic case, the output of one of the microphones was fed to both ears of the subject. For both signals, the MLD was found to be approximately 3 dB. Results will be discussed in terms of a decorrelating effect produced by longterm reverberation.
Vowel perception in consonantal context
Authors: Mermelstein Paul
Published: October 2005

Consonant-vowel-consonant syllables manifest formant frequencies in the center of the vowel region that differ from those of the vowels spoken in isolation [K.N. Stevens and A.S. House, J. Speech Hear. Res. 6, 111–128 (1963)]. It has been reported that subjects adjust their categorization of the [U]-[I] vowel continuum in consonantal contexts in a way that compensates for the undershoot of vowel target frequencies [B.E.F. Lindblom and M. Studdert-Kennedy, J. Acoust. Soc. Am. 42, 830–843 (1967)]. Do subjects hear the context-embedded vowel as having formant frequencies that are not in fact reached or do they merely adjust their categorization criteria? Listeners were asked to adjust the first two formant frequencies of a synthesized steady vowel to match the color of the vowel heard in the syllabic context. The results do not in general support the undershoot hypothesis. Some significant shifts from the nuclear-vowel formant frequency values to the perceived formant-frequency values are noted in the opposite direction. The result suggest that instead of indicating extrapolated target values, the matched formant values correspond to some appropriate time-average of the time-varying formant frequencies. [Work supported by ARPA, D. of Defense, and NIH.]
Question of asymmetries in auditory evoked potentials to speech stimuli
Authors: Smith Timothy S. , Neilson Brooke , Thistle Anne B.
Published: October 2005

It has been claimed that the auditory evoked potentials (EPs) to CV syllables differ by task (phoneme vs pitch discrimination) at left, but not right, hemisphere electrode sites [C.C. Wood, W.R. Goff, and R.S. Day, Science 173, 1248–1251 (1971); C.C. Wood, J. Exp. Psychol. 104, 3–20 (1975)]. In the present experiment, ten subjects heard synthetic CV syllables identical to those used in the Wood, Goff, and Day (1971) study. The tasks were also identical. Subjects performed a speeded choice reaction time task discriminating between the syllables /ba/ and /da/ or /ba/ (low pitch) and /ba/ (high pitch). EEG recordings (DC-48 Hz) were made from the international 10–20 system electrode sites C3 and C4 during these tasks, and EPs were averated only to the /ba/ (low-pitch) stimuli in either condition. Preliminary analysis of the results from eight of the subjects shows no significant differences between tasks at either electrode site. These preliminary results are not in agreement with the published findings cited above. [Work supported by the NIH.]
Occupational experience with a specific phraseology: Group differences in intelligibility for synthesized and human speech
Authors: Simpson Carol A.
Published: October 2005

Assuming a model of speech perception in which the listener's linguistic and pragmatic expectations reduce the uncertainty in the decoding process, it was hypothesized that listener-familiarity with a particular type of phraseology would affect intelligibility of novel utterances in that phraseology. Two groups listened to sentences of two types—common phraseology and specialized phraseology appropriate for air traffice communications and cockpit annunciator messages. Subjects in the experimental group were commercial airline pilots. Those in the control group were police officers. Requirements for the two groups were equivalent regarding age, sex, education, and experience with two-way communications using radios with poor frequency response and low S/N ratios. Half the subjects in each group heard the sentences as spoken by an air traffic controller. The other half heard the same sentences as produced by a VOTRAX speech synthesizer. Articulation scores for the common phraseology for the two occupational groups showed no significant difference. In contrast, the data showed a strong effect resulting from familiarity with the specialized phraseology. This suggests group differences in the “linguistic competence” utilized by the analysis-by-expectation speech perception process.
Perceptual characterization of fundamental frequency contours of disyllabic words
Authors: Campbell H. W.
Published: October 2005

Similarity judgments have been obtained for a number of pitch contours of the same word by using a triadic comparison method. Naturally spoken disyllabic words were analyzed by linear predictive coding, the fundamental frequency of the stressed syllable of each word was modified, and the words were then resynthesized. The slope and/or the maximum of the fundamental frequency contour for each stressed syllable was systematically varied. The data indicate that each of these factors contributes independently to the judgment of the similarity between two pitch contours.
Discriminability, response bias, and phoneme categories in voice-onset-time discrimination
Authors: Wood Charles C.
Published: October 2005

Considerable theoretical importance has been attached to the “phoneme boundary effect,” in which discrimination across a boundary between phoneme categories is superior to discrimination of comparable stimulus differences with a phoneme category. In order to asses the relative contribution of increases in discriminability and changes in response bias to the phoneme boundary effect, a “same-different” task compared discrimination of 300-msec synthetic syllables varying in voice-onset time (VOT) from −50 to 70 msec. Both a marked increase in discriminability and an equally marked shift in response bias toward “different” responses occurred at VOT values near the phoneme boundary. A second experiment investigated the role of phonetic categorization per se in the phoneme boundary effect. Variations in VOT were isolated from syllable context by eliminating the final 180 msec of steady-state vowel information from each stimulus. An increase in discriminability comparable to that of the first experiment was obtained for isolated VOT values corresponding to the phoneme boundary. Together with the recent data of Miller et al. [J. Acoust. Soc. Am. 55, 390 (1974)], these results suggest that the phoneme boundary effect for VOT does not depend exclusively upon phonetic categorization but may reflect a more general property of auditory temporal sensitivity.
Phonetic adaptation measured on two continua between the same syllables
Authors: Ganong W. F.
Published: October 2005

Two phonetic continua, ranging from /bow/ to /gow/ were synthesized. One coatinuum's stimuli varied. only in the frequencies of the burst and second formant transitions, while the other continuum's stimuli differed in the duration and spectral shape of the burst, and the duration (but not frequency) of the formant transitions. The boundary shifts induced by adaptation with each of the extreme /bow/'s and /gow/'s were measured. Each continuum's boundary was shifted more by adaptation with its /gow/ than with the other /gow/, as an acoustic account of adaptation would predict. The two /bow/'s, however, each moved both boundaries approximately the same amount, as a phonetic account would predict, This apparently paradoxical result can be explained by the assumption (which is supported by discrimination test data) that the two /bow/'s are perceptually more similar than the two /gow/'s.
Perceptual basis of vowel-duration differences
Authors: Javkin Hector
Published: October 2005

Lisker [Glossa, 8(2), 233–246 (1974)] has shown that there existed no viable explanation of vowel duration differences associated with the voicing state of the following consonant. Lisker's conclusion, that such differences are due to constraints of English, does not adequately explain such differences in other languages. Scully [Stockholm Speech Commun. Sem. 327–234 (1974)] suggests that such differences are due to the different aerodynamic conditions that occur depending on the voicing state of the following consonant. Scully's aerodynamic model does not provide resulting entirely consistent with speech data, however, and is therefore open to question. A different kind of explanation may be needed. Experimental evidence from 12 English speakers suggests that voiced (voiceless) consonants make the preceding vowel appear to be longer (shorter). Although these results have yet to be tested with speakers of other languages, they support an interesting hypothesis: the voicing of the following consonant, by continuing the voicing cue present in the vowel, may create the illusion of greater length. Such an illusion, acting as an input to phonological acquisition, may explain the observed vowel duration differences. [Work supported by NSF.]
Simple and contingent adaptation effects in speech perception
Authors: Pisoni D. B. , Sawusch J. R. , Adams F. T.
Published: October 2005

We report three experiments that employed a contingent adaptation procedure to study the interactions between auditory and phonetic processes. In this procedure, two alternating stimuli are presented as adaptors and their combined effects on perception can be studied. Experiment I examined the voicing feature in stop consonants and replicated previous findings indicating that adaptation of voicing takes place in a vowel-dependent manner. Two other experiments extended the contingent procedure to an analysis of the place feature. In one experiment simple and contingent adaptation were studied in order to show that the effects obtained with single adaptors can be canceled by the presentation of a contingent sequence containing identical vowels. Finally, in another experiment, the vowel context of the contingent adaptors and test series was manipulated. Differential adaptation effects were observed for two separate place series. The direction of the shifts in each series was governed by the vowel context of the adapting syllables indicating that selective adaptation of the place feature is also carried out in a vowel dependent manner. The results of these contingent adaptation experiments suggest that a large component of the selective adaptation effect takes place at an auditory stage of perceptual processing prior to phonetic analysis. [Research supported by NINCDS Grant NS-12179.]
Identification of vowels in CV and VC syllables
Authors: Strange W. , Jenkins J. J. , Edman T.
Published: October 2005

Previous research [W. Strange, R. Verbrugge, and D. Shankweiler, “Consonant environment specifies vowel identity,” Status Rep. Speech Res. Haskins Lab. SR 37/38, 209–216, (1974}] showed that isolated steady-state vowels were misidentified far more often than were vowels produced by the same talkers in a fixed consonant frame, /p-p/. Phenological and acoustic hypotheses suggest opposite differential contributions of the initial and final consonants in aiding vowel identification. In the present study, we compared the identification of nine American English vowels spoken by six adult talkers in four conditions: /p/-vowel, vowel-/p/, /p/-vowel-/p/, and isolated vowels. Isolated vowels and vowels in /p/-vowel syllables yielded approximately twice as many errors as vowels in the /p/-vowel-/p/ condition; vowels in vowel-/p/ context were identified almost as well as in the /p/-vowel-/p/ syllables. Errors for individual vowels in each of the conditions were analyzed to determine whether phonological constraints could accounts for the results. [Work supported by NIMH, NICHD.]
Another look at the acoustics of open plan schools
Authors: Walsh David P.
Published: October 2005

The open plan school has been with us now for over ten years, and the number of these schools being built per year is still on the increase. However, the acoustical environment of these spaces has received criticism with regard to high noise levels which result in annoyance, distraction, and speech interference. Even though the usage of open plan school spaces is quite different from that of open plan offices, the acoustical design recommendations for schools have generally been based on requirements for open plan offices. It appears that other considerations should be investigated for defining an acoustical environment acceptable for educational purposes. Our work has concentrated primarily on noise levels and annoyance in open plan classrooms. Direct relationships between noise levels, class size, student age level, and room finish treatments have been developed from extensive measured data. The subjective factor of annoyance has also been investigated and is related to background noise level and peak level fluctuations. Further investigations on the effects of room shaping are discussed as are statistical distributions of class noise.
On the design of structures to achieve a low-vibration level environment
Authors: Porter Michael A.
Published: October 2005

Recent trends in the design and production of micro scale precision devices, especially in the electronics industry, have severely taxed the ability of standard design structures to provide a suitably low-vibration level environment. The sensitivity of many research and production devices is such that both the traditionally considered sources (such as nearby highway or railway traffic and building mechanical equipment) and the sources not often considered before (such as pedestrian foot traffic in the building and low-frequency wind and acoustic excitation) are becoming problematic. The approach taken to anticipate and alleviate such problems in a recently constructed facility is discussed. The sources of vibration included most of these already outlined above, as well as the presence of a nearby artillery practice range. Specific examples of the steps taken to minimize potential problem areas are given as well as an analysis of the degree of success achieved.
Voiced-unvoiced decision without pitch detection
Authors: Atal B. S. , Rabiner L. R.
Published: October 2005

In speech analysis, the voiced-unvoiced decision is usually performed in conjunction with pitch analysis. The linking of voiced-unvoiced decision to pitch analysis not only results in unnecessary complexity but makes it difficult to classify short speech segments. We present a method of classifying a short speech segment, typically 10 msec in duration, into three classes: voiced, unvoiced, and silence. For each of the three classes, a nonEuclidean distance is computed from the measurements made on the speech segment to be classified and the segment is assigned to the class with the minimum distance. The distance metric used is given by (x − μi)t Wi−1(x − μi) where x is the vector representing the speech measurements, μi is the mean vector, and Wi is the covariance matrix for the ith class. The speech parameters are the zero-crossing rate, the speech energy, the correlation between adjacent speech samples, the first predictor coefficient, and the prediction-error energy. A training set of data is used to obtain the mean vectors and the covariance matrices for the three classes. A simple median-smoothing algorithm is used to eliminate isolated errors. The method has been found to provide reliable performance for both speech synthesis and speech-recognition applications.
A fast frequency domain pitch algorithm
Authors: Gillmann Richard A.
Published: October 2005

An algorithm for the extraction of fundamental frequency (pitch) from digitized speech is described. The computer algorithm operates in the frequency domain using autocorrelation spectra and is optimized for computational efficiency. Three basic operations are performed: (1) the digitized speech is low-pass filtered and down-sampled to a rate of 2000 samples per second, thereby eliminating frequencies outside the range of possible fundamentals and reducing the quantity of data to be processed. (2) Autocorrelation spectra are computed every 10 msec and pitch values are extracted. (3) The values of fundamental frequency obtained above are edited to eliminate anomalies. Reliability in terms of making the correct voiced/unvoiced decision exceeds 99%, and the program runs in about 14 times real time on a 16-bit minicomputer.
Analysis of 1500 phonetic errors in spontaneous speech
Authors: Shattuck-Hufnagel S. R. , Klatt D. H.
Published: October 2005

Fifteen hundred phonetic substitution errors were collected from spontaneous conversations of adult native speakers of English and formed into a confusion matrix of target versus intrusion phonemes. The matrix was analyzed using several methods for evidence of distinctive feature constraints on substitution patterns. Results are compared with evidence from studies of phoneme confusions in perception and in short-term memory. For many features, a substitution in the consonant matrix is significantly more likely to preserve the feature value of the target than would be expected by chance, suggesting that at some point in the production process, segments are represented psychologically in terms of features. The matrix formed by vowel substitutions, although smaller, also supports a traditional feature analysis, but the distinction between front and back vowels is often lost in substitutions. Other constraints which emerge from the error matrix include a sharp distinction between consonants and vowels, and little support for a strictly binary feature system.
Another consistency in phoneme duration
Authors: Umeda N.
Published: October 2005

With natural speech data for vowels and voiceless fricatives, we have shown that the durational behavior of phonemes in fluent speech is very regular when they are classified according to detailed phonological conditions, and that it can be approximated by simple rules [Umeda, J. Acoust. Soc. Am. 58, 434–445 (1975); J. Acoust. Soc. Am. 53, 378(A) (1973)]. Here we report further evidence of consistency in phoneme duration using three groups of consonants that have a closure along the vocal tract—voiceless stops, voiced stops, and nasals—taken from a 20-min reading by one speaker. Each group has three members: bilabial, dental, and velar. The durational relation between the members, when they do not form clusters with other consonants and when they are classified by stress and boundary conditions, shows a striking similarity across the three groups. The influence of adjacent consonants on the duration of the member is considerable. The variation depends on the relative “consonantalness” of both consonants, and on their manner of excitation and articulation.
Some acoustic properties of boundary signals
Authors: Forrest K. , Umeda N.
Published: October 2005

In a previous study, listeners' perception was used as an indicator of boundary signals in continuous speech [J. Acoust. Soc. Am. 56, Suppl. S33(A) (1974)]. While each subject had his own definition of the term “boundary,” there was high agreement among listeners about boundary locations. On the basis of those results, we investigated some acoustic parameters (relating to speaker's production) associated with boundary placement. The change in fundamental frequency was measured, in the word preceding the boundary, from the last stressed vowel to the end of the word. For comparison, measurements were also made in content words that were not followed by a boundary. Preliminary results show a greater fundamental frequency change (downward, upward, or both) at points where boundaries were perceived. Most of the perceived boundaries have a typical fall-rise pattern, i.e., from a maximum, occurring at the stressed vowel, the pitch decreases to a minimum level and then begins to rise again. However, at a small number of boundaries very little change in pitch was observed. Measurements were also made to determine the duration of the fundamental frequency excursion. It was found that the excursion was two to three times longer for a word preceding a boundary than when no boundary was present. The data suggest specific cues, both within and across words, that are relevant to boundary perception.
Intracellular study of synaptic events related to phase-locking responses of cat cochlear nucleus cells to low-frequency tones
Authors: Britt R.
Published: October 2005

Intracellular recording techniques were used to record from 55 cochlear nucleus cells in 46 pentobarbital anesthetized cats. Computer-generated peristimulus-time histograms, stimulus phase-locked histograms, and interspike interval histograms were used to study each unit. For units which show phase locking of discharges an excitatory postsynaptic potential (EPSP) is generated in response to each period of the sine wave. With lower-frequency stimulation, the probability of a unit discharge occurring with each EPSP was high but never exceeded 0.8. As the frequency of the stimulus increased, the probability of firing to a given period dropped, even though the period of the stimulus was much longer than the refractory period of the neuron. Units showed variable degrees of phase locking. Primary-like units of the same low characteristic frequency might or might not phase lock to the characteristic frequency. Units which showed phase locking at lower frequencies but not at higher frequencies often also changed response configuration from primary to onset, built-up or pause. A decrease in stimulus intensity caused a decrease in the amplitude of the EPSD and a lowered probability of firing. Both the EPSP and the phase-locked unit discharge can contribute to the frequency-following response recorded with macroelectrodes in the cochlear nucleus. [Work supported by Bank of America—Gianinni postdoctoral fellowship.]
Effects of intensity on responses of anteroventral cochlear nucleus (AVCN) neurons to clicks and noise
Authors: Dickson J. W. , Ruggero M. A. , Wickesberg R. E.
Published: October 2005

Using clicks and noise at various intensities, we studied impulse responses of phase-locking AVCN neurons in barbiturate-anesthetized cats. AVCN click responses are similar to responses of the cochlear nerve: near threshold post-stimulus time (PST) histograms show multiple peaks separated by the period of the unit's best frequency. With increasing click intensity, both earlier and later peaks appear. At high intensity, the initial peaks are much larger than the later peaks. The linear impulse response of the system may be calculated by cross-correlating a Gaussian white-noise input with the output. The cross correlations, determined by calculating the average stimulus waveform preceding a spike, appear as oscillatory transients with spindle-shaped envelopes. At low noise intensity the maxima and minima correspond in time, and generally in shape, to the peaks of low-intensity rarefraction and condensation click PST histograms. As the noise intensity increases, earlier oscillations appear, but the early peaks are not as exaggerated as in the PST histograms and additional late oscillations are not apparent. [Supported by NIH.]
Response properties of single neurons in anteroventral (AVCN) of the newborn cat: Frequency selectivity and temporal ordering of discharges
Authors: Javel Eric , Brugge John E. , Kitzes Leonard M.
Published: October 2005

In the cat, anatomic development of the peripheral auditory system, including the cochlear nuclei, proceeds for weeks after birth. We describe here some properties of functional maturation of responses to pure tones of AVCN neurons in kittens ranging in age from 4 to 30 days. In kittens less then one week old, AVCN units possessing best frequencies below 2000 Hz are somewhat more broadly tuned than are units found in the adult. Furthermore, thresholds at best frequency are greatly elevated (typically greater than 100 dB SPL), saturation discharge rates are relatively low, and the average latent periods to the first spike are relatively long. By the end of the third postnatal week these response properties are similar to those obtained in the adult AVCN. In kittens less than two weeks of age, the discharges of units resposive to low-frequency tones are securely locked in phase for frequencies below 300 Hz; however, phase locking declines rapidly at higher frequencies and is generally absent above 1000 Hz, even though units may still be responding vigorously to the tone. The range of frequencies to which phase locking may be observed increases with the age of the animal, but, during the first 30 days postpartum, the degree of phase locking is, with few exceptions, poorer than that obtained in adult animals.
Effects of sectioning the dorsal stria on responses of cells in inferior colliculus to binaural clicks
Authors: Bengry M. F. , Silverman M. S. , Clopton B. M.
Published: October 2005

In order to estimate the relative contribution of brain-stem pathways to binaural interaction at the inferior colliculus, we severed the dorsal stria in anesthetized rats and examined binaural interaction at the inferior colliculus. Extracellular recording was contralateral to the lesion using monaural and binaural clicks of varying intensity as stimuli in order to access the suppression of firing usually caused by ipsilateral stimulation. Both averaging and categorization of cell responses indicated that they underwent a greater reduction of firing when stimulation of the ear ipsilateral to the recording site was added to contralateral stimulation than did unlesioned controls. Since cells from lesioned animals also had click thresholds that were higher than controls, and since this pathway has only minor, if any, projections to the region of binaural interaction in the superior olivary complex, our results suggest that binaural interaction seen at the inferior colliculus does not entirely mirror binaural integration performed at the superior olivary complex. The dorsal stria contributes to this interaction. [Work supported by NIH.]
Effects of behavior performance on single-unit firing patterns in the inferior colliculus of the Rhesus monkey: additional observations
Authors: Ryan Allen
Published: October 2005

In a previous report [J. Acoust. Soc. Am. 55, 468 (1974)], it was noted that performance in an auditory reaction-time task tended to increase both the evoked firing rate and initial latency of single-unit responses to acoustic stimuli in the inferior colliculus and medial geniculate nucleus of rhesus monkeys, while the spontaneous rates of these units were unaffected. Our sample of chronically recorded collicular units has been expanded and our earlier findings were in general confirmed. However, more specific effects of performance were noted. “Off” responses were consistently, and sometimes strikingly, suppressed in the performance condition when compared to responses to identical stimuli delivered while the animal sat passively. Moreover, in some units increases in evoked firing rate were confined to specific temporal portions of the response pattern, and might be offset by suppression of firing in other portions. Also, the timing of some neural events could be related to specific aspects of reaction time performance. [Work supported by NIH grant NS-08181.]
Hemispheric asymmetry of auditory function in monkeys
Authors: Dewson J. H. , Burlingame A. , Kizer K. , Dewson S. , Kenney P. , Pribram K. H.
Published: October 2005

On a test of recent auditory memory [J.H. Dewson and A. Burlingame, Science 187, 267–268 (1975)], some monkeys show a severe and enduring deficit following unilateral cortical ablation of the superior temporal gyrus (“auditory association cortex”). Six such operations have been performed, and the deficit exists in only those four instances in which the left cortical area has been removed. In two cases of unilateral ablation of the superior temporal gyrus of the right hemisphere, no performance decrements have been noted. Discrimination between very brief (2–3 msec) acoustic stimuli remains at normal (preoperative) levels for all animals regardless of the cerebral hemisphere damaged and, in general, at very short delays (less than 1 sec) on the auditory memory task, performance is maintained even by the deficient animals at their preoperative criterion levels. The deficit does not appear to depend upon the disruption specifically of either the crossed or the uncrossed ascending auditory pathway as determined by results obtained from unilaterally deafened monkeys. Preliminary investigations of the nature of the deficient recent auditory memory suggest that interference at the time of retrieval is a major element. [Work supported by NSF.]
Acoustic scattering in the ocean
Authors: Hurdle B. G. , Flowers K. D. , DeSanto J. A.
Published: October 2005

A review of acoustic scattering from the surface, bottom, and volume of the ocean is given. Scattering problems in underwater acoustics are delineated and discussed relative to present scientific capabilities. Areas of deficiency are cited.
Multiple scattering from a random interface
Authors: DeSanto John A.
Published: October 2005

The problem of scattering sound from a random interface separating two fluids with different densities and sound speeds is considered. The interface height is Gaussian distributed. The mathematical approach is the construction of the Green's function G for the problem by applying Green's theorem in both fluids to G and a single free space Green's function. Mixed surface-volume integral equations are derived in coordinate space using continuity conditions on G and its normal derivative. In Fourier transform space, these equations can be combined to yield a single three-dimensional integral equation for a singularity-free function Γ linearly related to G. Using cluster decomposition techniques yields the Dyson integral equation for the coherent part (mean, first moment) of Γ and the Bethe-Salpeter integral equation for its second moment. The Born terms and kernels of both these equations can be represented as infinite series of Feynman-like diagrams. The first diagram corresponds to a Kirchhoff approximation. Using it in the Dyson equation yields a one-dimensional integral equation which can be solved numerically. This multiple-scattering-Kirchhoff solution, in the case of a Neumann boundary, yields more coherent specular intensity for large values of the Rayleigh roughness parameter than the single-scattering-Kirchhoff approximation, and can be used to account for diverse experimental data. This as well as further results are discussed, the main point being the necessity of taking multiple scattering into account for problems of this type.
Backscatter of an impulsive wave at a rough surface
Authors: Clay C. S.
Published: October 2005

An extension of Eckart's scattering theory that includes sphericity of the wave front (Fresnel approximation) shows agreement with experimental data within a few percent. These laboratory experiments are made with long ping and approximately meet the continuous wave condition of the theory. In applying the theory to the interpretation of side scan sonor data, I decided that the c.w. assumption didn't apply because the insonified area is not insonified at the same time. Solutions for an impulsive point source and receiver at the same location are a good approximation to the problem. Trorey [Geophys. 25, 762 (1970)] and Hilterman [Geophys. 25, 1020 (1970)] give expressions for the boundary wave scattered at a segment of a plane. We use these expressions in two ways: We calculate the spectra of signals scattered from different sizes of planes. We use segments of planes to model rough surfaces. The theoretical signal wave forms and amplitudes agree with experimental measurements. [Research supported in part by NSF grant GA 39889.]
Scattering of acoustic waves by randomly rough surfaces
Authors: Welton P. J.
Published: October 2005

The scattering of acoustic waves by randomly rough surfaces has been investigated using an integral equation approach similar to the Helmholtz integral formula. For the calculation of the mean scattered intensity to remain analytically tractable, numerous approximations must be introduced. The five important quantities most often approximated in the scattering integrals are (1) the surface slopes, (2) the phase function, (3) the source directivity function, (4) the probability density function of surface heights, and (5) the surface autocorrelation function. The results to be discussed in this paper are based on an exact representation of the surface slopes, a Fresnel phase approximation valid for specular, forward, and backward scattering, a Gaussian source directivity approximation, both Gaussian and non-Gaussian surface statistics, and a general representation of the autocorrelation function. Several new results have been obtained and these provide considerable insight into the significance and consequences of the various approximations used in scattering calculations.
Broad-band pulse techniques in model scattering research
Authors: Zornig J. G.
Published: October 2005

A number of statistical properties of sound scattered from wind driven water surfaces have been studied using a broad-band preemphasized probing pulse technique. These studies, conducted in a small scale model tank, have shed light on cross frequency and spatial correlations of the scattered field and on the fading behavior of received signals. The pulse-forming technique [Zornig and McDonald, J. Acoust. Soc. Am. 55, 1205–1211 (1974)] has been refined and applied to additional measurements of forward scattered fields. Using surface data obtained with a high-resolution waveheight probe comparison has been made with theoretical predictions [McDonald and Tuteur, J. Acoust. Soc. Am. 57, 1025–1029 (1975)] showing good agreement. Construction of a large computer controlled acoustic goniometer has made it possible to conduct high-resolution spatial surveys of scattered field statistics as a means of validating theory. [Work supported by ONR.]
Theory of reflection and transmission at rough boundaries with application to sound propagation in the ocean
Authors: Kuperman W. A.
Published: October 2005

The interaction of an acoustic field with a randomly rough two-fluid interface is studied. A perturbation method is used to replace the flat interface boundary conditions with a new set of boundary conditions on the mean interface. These new conditions are valid for surfaces characterized by arbitrary correlation functions and are therefore not restricted to the Kirchhoff regime. Using these boundary conditions plane wave reflection and transmission coefficients are derived. The pressure release case is extracted by letting the density of the second medium vanish. It is shown that in the Kirchhoff approximation the reflection and transmission coefficients reduce to those obtained earlier by Eckhart, Clay, Medwin, and Hagy. These same boundary conditions are also used to solve the wave equation for a point source placed in an ocean duct with rough boundaries. Using a normal-mode solution, the effect is to add an imaginary part to the modal wavenumbers which can be interpreted as a modal attenuation coefficient. Calculated results are presented for the single interface and for realistic ocean ducts where attenuation in the bottom sediment is also included.
Community-aircraft noise exposure modeling with the NOISEMAP computer program
Authors: Reddingius Nicolaas H.
Published: October 2005

The NOISEMAP computer program is one of the tools of a comprehensive U.S. Air Force program for assessing the noise exposure in the vicinity of air bases. NOISEMAP provides a state-of-the-art mathematical model for describing community noise exposure in terms of Ldn or NEF contours. Shortcomings of earlier computer programs in handling of ground runups, airport traffic patterns, parallel runways, and dispersion of flights were specifically addressed. The program allows for the input of IFR clearances and standard instrument departures (SIDs) directly, in addition to the more usual descriptions of flight paths. To aid land-planning studies, such features as limited area calculations, dumps of noise exposures at any time during the calculation, and the ability to save the output in machine readable form for further processing are included. These features also enable one to assess the effectiveness of operational changes for a particular aircraft without having to recompute the noise contribution of aircraft unaffected by the changes. [Work supported by the Aerospace Medical Research Laboratory, Wright-Patterson AFB.]
Subjective ratings of the annoyance of helicopter flyby noise
Authors: Patterson J. H. , Mozo B. T.
Published: October 2005

Basic data was collected to be used in the prediction of annoyance associated with helicopter flyby noise. A C-47 (DC-3) was flown over a fixed course to generate a reference sound for rating the helicopter noises. Five different types of military aircraft were flown in a set of controlled flight patterns to generate the helicopter noises. A relative scale of annoyance was used for listener responses. Twenty-five listeners rated each approximately 200 helicopter flybys over a 30-day period. Each flyby was tape recorded during these listening sessions for later analysis, The tape recordings were analyzed and a variety of predictors of annoyance was calculated for comparison to the subjective ratings. Data showing how the various predictors compared with listener ratings will be presented. [This project was conducted in cooperation with the Construction Engineering Research Laboratory, Champaign, IL at Ft. Rucker, AL.]
Noise work due to single automotive vehicles driving by and aircraft flying overhead
Authors: Lane S. R.
Published: October 2005

In California, the level of integrated noise intensity-time function (noisework), called Single Event Noise Exposure Level (SENEL), is used as an indicator of the noise impact due to individual noise sources (air and ground vehicles) passing by. For the simple case, SENEL = SPLA MAX + 10 logπR/V, where R and V are the distance to and speed of the vehicle. A previously published expression for SENEL is incorrect. Analyses of recorded samples of autos, trucks, and light aircraft show that the correct analytical expression predicts SENEL values within ±1 dB of measured values. For commercial jet aircraft landing noise samples recorded at LAX, the theoretical SENEL values were 1–2 dB greater than the experimental values, whereas similar data reported by the FAA indicated theoretical SENEL values 2–4 dB greater than the corresponding experimental values.