bluuebunny/crossref_metadata_2025 huggingface dataset:
Active acoustic receivers
Authors: Westervelt P. J. , Thompson L. A. , Muir T. G.
Published: October 2005

The acoustic power P radiated by a simple source of strength Q immersed in an external sound field of pressure p is P = P0 + pQ, in accordance with energy conservation. Here, P0 represents the power radiated by the simple source operating along, that is, with p = 0. If p and Q oscillate at frequencies f1 and f2, respectively, and if Δf = |f2 − f1| ≪f2, the power supplied to the simple source will be modulated at the frequency Δf with a fractional amplitude equal to pQ0/2P0. The power supplied to the oscillator or amplifier driving the simple source will likewise be modulated at Δf, with a fractional amplitude related to pQ0/2P0 through the characteristics of the amplifier. Experiments were conducted with an external sound field produced by a piston projector and a simple source radiating in water at ultrasonic frequencies. The dc current supplied to a class AB power amplifier driving the simple source was monitored for the Δf component. Measured data on the amplitude response obtained by varying p and Q0, and beam pattern data obtained by varying the orientation of the piston beam, support this formulation of the active receiver.
Effects of three activities on annoyance responses to recorded aircraft flyovers
Authors: Gunn Walter J. , Shepherd William T. , Fletcher J. L.
Published: October 2005

Subjects participated in an experiment in which they were engaged in TV viewing, telephone listening, or reverie (no activity) for a one-half-hour session. During the session, they were exposed to a series of recorded aircraft sounds at the rate of one flight every two minutes. Within each session, four levels of flyover noise, separated by 5-dB increments, were presented several times in a Latin-square balanced sequence. The peak level of the noisiest flyover in any session was fixed at 95, 90, 85, 80, 75 or 70 dBA. At the end of the test session, subjects recorded their responses to the aircraft sounds, using a bipolar scale which covered the range from “very pleasant” to “extremely annoying” Responses to aircraft noises were found to be significantly affected by the particular activity in which the subjects were engaged. Furthermore, not all subjects found the aircraft sounds to be annoying.
Community noise measurements at 100 sites throughout the United States
Authors: Simpson Myles A.
Published: October 2005

In an attempt to develop and test a model of outdoor noise exposure in residential urban and suburban areas (not primarily exposed to the noise from airports or highways), noise measurements for 24-hour periods were acquired at each of 100 sites located throughout the continental United States. The measurement sites were spread among 14 cities, and were selected to span a wide range of population densities (1000 to 90 000 people per square mile). The data were acquired with portable unmanned monitoring systems which sampled the noise environment eight times per second for a full 24-hour period. The day/night sound levels observed among the locations ranged from 50 to 75 dB. L1, L10, and L50 were found to be highly correlated with the equivalent level (correlation coefficient 0.9 or higher). L10, L50, L90, and Ldn were all correlated at coefficients greater than 0.7 with the logarithm of population density, while the noise pollution level showed a much lower correlation coefficient (order of 0.5). [This work was supported by the Environmental Protection Agency.]
Practical aspects of exterior mechanical equipment for compliance with the New York City Building Code—Noise Control Section
Authors: Morlock Henry M. , Peppin Richard J.
Published: October 2005

The Noise Control Section of the New York City Building Code is presented from a consultant's point of view. The code, as written, is briefly explained, and problems associated with determining exterior mechanical equipment noise compliance are presented, Recommendations for code interpretation as well as suggested methods for equipment compliance, not specifically spelled out in the code, are presented to provide a workable and less ambiguous method for equipment qualifications. A flow chart indicating possible testing methodology is also included.
Noise prediction in ships
Authors: Kihlman Tor , Plunt Juha
Published: October 2005

A research program has been organized by the Swedish Ship Research Foundation. One of the objectives of the program has been to develop a noise prediction method. In its first form this prediction method is of empirical type, based on extensive noise level and vibration measurements in three reference ships. It has the form of a computer program. Depending on ship type, somewhat different propagation models can be chosen. The vibration measurements in the reference ships reveal some of the fundamental difficulties in getting an accurate calculation method. The different stops in the calculation also have rather different accuracy. The radiation of sound from the linings can be accurately predicted; however, predicting the structure-borne transmission in the steel hull and from the steel construction to the linings involve greater uncertainties. One of the reasons for this is the unexpectedly high level of inplane waves in the steel structure (longitudinal and transverse waves). [Compare to T. Kihlman and J. Plunt, “Structure-borne sound in ships: Study of different waveforms,” ICA 8 (1974).]
Effect of behavioral measure sensitivity on the prediction of speech understanding through low-fidelity circuitry
Authors: Smaldino J. J.
Published: October 2005

There is disagreement in the literature as to which hearing-aid performance characteristics are most predictive of speech understanding. Among the reasons suggested for the disagreement is the absence of a standard measure of intelligibility in these studies. Presumably scores obtained on different behavioral measures are selectively influenced by separate electroacoustic interactions. Results of analyses relating several behavioral measures to performance indices might be expected to inconsistently rank order the relative influence of the indices as predictors of intelligibility because of the selective potency of the interactions. The present study reports factor and multiple regression analyses conducted between 42 discrete hearing-aid performance indices and eight measures of speech understanding. Factor groupings were harmonic distortion, maximum power output, bandwidth, gain, and regularity of frequency response. Prediction of speech understanding based upon these five factors ranged from moderate [R = 0.69] to strong [R = 0.98] across the behavioral measures. Normalized beta weights indicated that harmonic distortion had the highest relative influence on seven measures of intelligibility. The other four factors showed no consistent pattern of influence and lend support to the presumption that comparison of predictive potential of performance indices based upon different behavioral measures can be misleading.
Intelligibility of 1/3-octave-band filtered speech
Authors: Chari N. C. A. , Herman G. , Danhauer J. L.
Published: October 2005

Seventeen English consonants were paired with the vowels /i a u/, and presented in three contexts—CV syllables, CVC words, and CVC words in sentences. Stimuli were presented in five 1/3-octave-, one critical-, and one wide-band filtered conditions. Twelve paid, normally hearing college freshmen listened monaurally at a comfortable level and provided written responses to the stimuli. Statistical analysis showed (1) sentences were perceived significantly more correctly than CV and CVC stimuli regardless of filter condition, and (2) there was no difference between the CV and CVC data. A maximum intelligibility score of 50, 5% was obtained for CV and CVCs in the 1/3-octave band centered at 2000 Hz. Additionally, scores for 1/3-octave bands centered beyond 2000 Hz were higher than those centered below 2000 Hz. Results were compared to earlier studies [K. D. Kryter, J. Acoust. Soc. Am. 32, 547–556 (1960); W. E. Castle, J. Acoust. Soc. Am. 36, 1047(A) (1964)] with respect to variations in intelligibility scores as a function of center frequency and bandwidth. Consonantal perceptual parameters derived from an analysis of the subjects' error data will be discussed in a separate paper.
Normal-hearing subjects' perceptual parameters for 17 English consonants perceived in conditions of 1/3-octave-band filtering
Authors: Danhauer J. L. , Chari N. C. A. , Herman G.
Published: October 2005

Perceptual parameters were derived from confusion data based on 12 normal-hearing subjects' responses to 17 English consonants and three vowels presented in a CV syllable context, and perceived through five 1/3-octave- and one critical-band filter conditions. Two INDSCAL analyses were performed on the pooled data of the 12 subjects treating the six filter conditions as separate groups. For the first analysis, consonantal confusion errors were analyzed separately for each of the three vowels. In order to find common perceptual parameters, a second analysis was performed by pooling consonantal errors for the three vowels. In both analyses, subjects' weightings of the perceptual parameters were found. The INDSCAL procedure was conducted in two- through seven-dimensional spaces. Primary perceptual features for the consonants included nasality, which was retrieved in both analyses, and voicing, which was retrieved in both analyses, with the exception of /a/ in the first analysis. For both analyses, other less prominent features were retrieved showing interactions of more than one feature, for example voiced-front.
Vowel perception in the absence of formants
Authors: Yilmaz Huseyin
Published: October 2005

Various vowels of a person were recorded and inverse filters for these vowels were constructed. An inverse filter destroys the formant structure of the corresponding vowel by reducing the output to a flat spectrum. Sets of experiments were performed with the help of a listening jury for (1) vowels in isolation through a given inverse filter—vowels for which the inverse filters were designed became unrecognizable; (2) vowels at normal rate through a given inverse filter—all vowels were recognizable; and (3) vowels at normal rate through randomly changed inverse filters-design vowels again became unrecognizable. The second set of experiments shows that (a) the formant plot concept is not adequate for vowel perception and (b) large vowel adaptations take place at normal speech rates. Details of the experiments are presented, and a new concept in which these experiments are easily explainable is indicated.
Experimental evaluation of information conveyed through voiced, unvoiced, and transition segments of speech
Authors: Ganesan K. , Lin Wen C.
Published: October 2005

Studies in the perception of speech have so far been only of a qualitative nature using psychoacoustic experiments. In this paper a quantitative method of making statistical measures is described. The technique uses the concepts of Shannon's information theory and a measure of information content is formulated. An algorithm based on statistical pattern recognition techniques is used to segment speech into four different segment classes [K. Ganesan and W. C. Lin, “Statistical pattern recognition approach to speech segmentation,” J. Acoust. Soc. Am. 56, S31 (A) (1974)]. Spectrograms of each type of segment are then obtained through which the corresponding probability density functions are estimated. Let Cv, Ct, and Cu be the voiced, transition, and unvoiced segment classes respectively. Information conveyed through Cv is given by I(X|Cv) =  ∑ x1,x2,x3 p(X) log p(X) −  ∑ x1,x2,x3 p(X,Cv) log p(X|Cv), where X = {x1,x2,x3}, a vector point in the spectral space. Applying this formulation to all the three classes, we found that the information conveyed through Cv is significantly lower than that through Ct and Cu, which are approximately equal.
Cocktail party acoustics
Authors: Crum Lawrence A.
Published: October 2005

This presentation for a lay audience first discusses certain rotations applicable to random noise sources in a rectangular enclosure, develops the concepts of masking noise, and the source-masking noise interaction, and then provides a calculation of the number of people that could be invited to a cocktail party in which comfortable source-source interactions are required. Finally, via a tape recording of some actual parties, the relations which have been developed are demonstrated.
Input impedance curves for the brass instruments and the behavior of mutes
Authors: Backus John
Published: October 2005

The equipment already described [J. Backus, J. Acoust. Sec. Am. 56, 1266 (1974)] has been used to obtain input impedance curves for the brass instruments. By plotting such curves for a piece of plain tubing, tubing plus trumpet bell, tubing plus mouthpiece, and tubing plus bell plus mouthpiece, the transition from the odd-multipled resonance frequencies of a closed tube to those characteristic of a trumpet is clearly shown. For a good trumpet “open”—no valves down—the resonances from the second up fit the harmonic series very closely; with all the valves down and the instrument correspondingly lengthened, the fit is considerably worse, This behavior is characteristic of the trombone and French horn also. Mutes as commonly used are hollow enclosures that behave like Helmholz resonators; impedance curves of a trumpet with mute show an additional peak due to the resonance frequency of the mute, and it is essential that this peak be below the playing range of the instrument so as not to distort its intonation. The primary function of a mute is to act as an acoustic filter which reduces the radiated output of the instrument at low frequencies relative to the higher frequencies and so produces a pronounced formant in the tone. [This work was supported by the National Science Foundation.]
Walsh functions in signal processing and electronic music
Authors: Lay J. E.
Published: October 2005

The class of functions, wal(k,t), of index k ⩾ 0 and argument t represents a complete set of orthogonal functions of the Hilbert space L2(−12,12). A signal function f εL2(−12,12) can consequently be represented by a generalized Walsh-Fourier series, with coefficients obtained from the usual criterion of minimum mean-square error. The theory of Walsh-Fourier series has a long tradition in mathematics, but it is the advance of semiconductor technology that has produced the first really new, useful set of orthogonal functions. Their importance is now being recognized in many applications, including the generation of periodic waveforms and envelope shapes for additive synthesis in electronic music. Walsh functions have many interesting properties. Seen mathematically, they represent in the main the characters of a specific locally compact Abelian group. However, from a pedagogical point of view, they can very simply be introduced through a discussion of orthogonal functions. For use in waveform synthesis, Walsh functions may easily be generated by means of bistable dividers and exclusive-or gates. For a given f(t), the series coefficients are obtainable from a fast Walsh transform algorithm.
Masked intelligibility threshold test: sensitivity and reliability
Authors: Chial M. R.
Published: October 2005

A new psychophysical technique, the Masked Intelligibility Threshold (MIT) test, was developed for assessment of speech transmission systems such as hearing aids. The test employs continuous discourse as a primary signal, and a competing noise whose spectrum approximates long-time average speech and whose amplitude envelope follows the associated speech signal. Subjects track the level of the primary signal to a subjective 50% intelligibility criterion. The dependent variable is a signal-to-noise ratio (S/N) which should increase as transmission system degradation increases. In preliminary experiments, untrained normal listeners were tested twice under conditions of (1) frequency distortion (low-pass filtering) and (2) amplitude distortion (linear rectification). Significant S/N differences were found in predicted directions as low-pass cutoff frequency varied from 10 kHz and 1 kHz to 700 Hz to 500 Hz. Similarly, S/N's differed significantly as total harmonic distortion varied from 15% to 1% and 40% to 63%. Within-trial reliability was high in beth experiments (r = 0.94 to 0.97). A significant learning effect was noted between trials (r = 0.51 to 0. 65).
Voicing and juncture in stop-lateral clusters
Authors: Darwin C. J. , Brady Susan
Published: October 2005

A study using synthetic speech was made of the acoustic cues underlying voicing and word boundary decisions in stop-lateral clusters. It was found that a longer voicing lag is necessary for a stop to be perceived as voiceless in a /tr/ cluster than when the /r/ is absent. The question of whether this change in the voicing boundary is due to differences in the acoustic elements cuing voicing (such as the F1 transition) or to a recalibration of the criterion for voicelessness after identification of the /r/ segment is examined. Some cues to the distinction between /♯tr/ and /t ♯ r/ and between /♯ dr/ and /d ♯ r/ are also discussed.
Automatic assessment of speech timing accuracy
Authors: Allen George D.
Published: October 2005

Our previous studies of speech timing accuracy have used measurements derived from oscillographic tracings of speech, a laborious and error-prone procedure. Hence we have designed a system, based on a laboratory minicomputer (PDP8/e), which automatically estimates the same temporal parameter (variance-per-unit-time). The heart of this system is a FOCAL program, modified by the addition of real-time subroutines to give instructions to the subject, monitor the temporal characteristics of his vocal behavior, and give him feedback related to either the rate or variability of that behavior. The program is slightly adaptive, in that, as the subject's performance improves, the standard of variability against which he is judged also improves, forcing him toward greater accuracy. Estimates so far obtained with this system are comparable with those of our earlier studies, suggesting that the variance-per-unit-time statistic is more characteristic of the speaker's ability than the experimental task.
Identification of vowels excerpted from context
Authors: Bond Z. S.
Published: October 2005

Subjects have been shown to have some difficulty in identifying vowels presented in isolation [Fairbanks and Grubb, J. Speech Hearing Res. 4, 203–219 (1961); Strange et al., J. Acoust. Soc. Am. 55, S53(A) (1974); Moore and Mundie, AMRL-TR-70-109 (Aug. 71)]. In all these studies, the speakers have produced the vowels in question with considerable precision. However, equivalent precision of utterance can not be assumed in more ordinary speech situations. In the present study, the effect of context on the identifiability of vowels was investigated. Six speakers produced ten monophthongal English vowels in two different phonetic contexts, h—d and nasal—nasal. The vowels were then excerpted from context and presented to subjects for identification. Subjects found the identification of these excerpted vowels to be quite difficult. The phonetic context, the abilities of the various speakers to produce vowels that could be readily identified as the intended vowel, and the vowels themselves, were all found to be significant factors in affecting subject performance.
Rhythmic factors in the determination of perceived stress
Authors: Cutler Anne
Published: October 2005

Previous work has shown that when subjects are required to comprehend sentences and press a button on hearing a word beginning with a particular sound, they react faster to targets on stressed words than on unstressed words. This experiment investigated the role of rhythm in determining perceived stress. Twenty-four sentences were recorded in a strict rhythm (one stress every 500 msec). In each sentence, two monosyllabic words occurred together (e.g., “The children were frigthened when they saw a black dog in the garden”); the second of these was stressed. A silent interval of 250 msec (half a beat) was spliced into a copy of each sentence immediately before the first of the two monosyllables. The target could be the sound beginning either the first or the second monosyllable. Thus, each sentence occurred in four versions—twice, with, twice without silent interval, and twice with first, twice with second target. Each subject heard only one version of each sentence. If rhythm is sufficient to determine perceived stress, reaction time to the first target (/b/ above) should be faster when the silent interval is present than without it, since the interval will cause the next accent to be expected half a beat early; reaction time to the second target (/d/ above), however, should be faster when the silent interval is absent. Exactly this interaction was found.
Use of conditional probabilities for stress-level prediction
Authors: Sargent Douglas C.
Published: October 2005

Several of the improvements made in the past year on a stress contour extraction algorithm capable of producing a three-level stress contour from continuous speech (stressed, unstressed, and reduced) are discussed. Emphasis is placed on the application of conditional probability decisions as a means of using adjacent syllables of known stress to determine the most likely stress level for those syllables whose stress could not be assigned from their acoustic correlates. Comparisons are made between the results obtained from the conditional probability decisions and the results obtained from application of other linguistic considerations, such as the proximity to other stressed syllables or the Alternating-Stress Rule. Stress extraction results from a 700-syllable test passage are presented, and a number of additional improvements in the routine's decision procedures are proposed.
Describing linguistic stress contours of different sentence structures
Authors: Cheung J. Y. , Minifie F. D.
Published: October 2005

Changes in the semantic or syntactic structures of sentences often result in corresponding changes in the linguistic stress contours. In the present study, two sentences were systematically varied from their declarative form to the three following forms: the command form, the YES/NO question form, and the WH-question form. These sentences were read when imbedded in a paragraph context. The recorded sentences were presented to listeners who perceptually rated the amount of linguistic stress on each syllable. These perceptual judgments were then modeled via an analysis of the general linguistic stress pattern. In spite of the different sentence structures, the results showed that all four forms of linguistic stress can be described by a general model composed of anticipatory and recency effects centered around local apexes. These local apexes are primarily the verbs in command sentences, the last content words in YES/NO questions, and the WH-word in WH-questions. In all forms except the YES/NO questions, the apexes appeared always at the position of their associated words even under semantic or syntactic changes. For the YES/NO question forms, the last content words were always stressed.
Asymmetrical analysis of stimuli with dichotically split formants
Authors: Haggard M. P.
Published: October 2005

Six split-formant /ba/—/da/ stimuli were constructed, differentiated by opposed or reduced F2 and F3 transition cues to place. These were synthesized with common F0 but F1F2 and F1F3 fed to different ears. F2 alone differentiated three of the possible stimulus pairings, and F3 differentiated three, enabling the ear underlying the response distribution to be specified. There were more “b” than “d” responses, and more pairings were off phoneme boundary when the critical cue stimulated the left ear. Bias-free measures on pairings close to boundary showed no greater differentiation of F2 or F3 pairings by the right ear, suggesting no asymmetry of primary auditory analysis. However, in individual stimuli with conflicting F2 and F3 cues, the cue presented to the right ear tended to control the response. This result, plus the asymmetrical bias, suggests that dichotic components of a speech pattern take different (presumably contralateral) paths to the speech processor even when spectral compatability and common voice source predispose subjective fusion.
Critical bandwidths measured by the pulsation threshold technique
Authors: Aldrich W. M. , Barry S. J.
Published: October 2005

The critical bandwidth centered at 1000 Hz was measured at 40 and 80 dB SPL in normal listeners by adapting the pulsation threshold technique of T. Houtgast to a masking experiment performed by D. M. Green [J. Acoust. Soc. Am. 37, 802 (1965)]. Masker and probe signals were alternated continuously in time; the duration of each was 150 msec. The probe signal was a 1000-Hz sinusoid arithmetically centered between two sinusoidal masker components whose frequency separation, Δf, ranged from 0 to 1000 Hz. At each of 12 Δf's, the subject adjusted the probe intensity for the highest level at which the probe was perceived as continuous. Pulsation thresholds obtained in this manner were plotted as a function of Δf. For Δf's within the critical band, the pulsation threshold remained near the SPL of the masker. For Δf's greater than the critical bandwidth, the pulsation thresholds decreased in a linear fashion with log frequency. Values of the critical bandwidth obtained were in good agreement with other direct measurements.
Pulse-width tracking procedure for determination of auditory threshold of brief tones
Authors: Yonovitz A. , Mitchell C. W.
Published: October 2005

Duration as a parameter was used to determine the temporal summation characteristics of normal ears. An apparatus was constructed that permitted a subject to track threshold by modulating pulse width. The apparatus permitted experimenter control of rate of pulse-width modulation and interpulse interval. The pulse width could be continuously varied by the subject from 10 to 500 msec. The rate of temporal summation was determined in 10 normal ears at octave frequencies between 0.125 and 8.0 kHz. Absolute thresholds were determined using a rate of change in pulse width from 4.5 and 30 msec per second. Subjects tracked threshold at a given intensity level for a time sufficient for the tracing to become stabilized. A constant off-time of 500 msec was used between pulses. The temporal summation patterns were found to be reliable and indicate potential clinical usefulness in the pathological ear.
Comparison of method-of-adjustment and forced-choice procedures in frequency discrimination
Authors: Wier C. C. , Jesteadt W. , Green David M.
Published: October 2005

Reported estimates of the difference limen for discrimination of a change in frequency of a pure tone show considerable variability. Studies using frequency modulation tend to estimate larger limens than do studies employing noncontinuous fixed-frequency stimuli. Even among the latter studies large differences are obtained when different methods are employed [J. D. Harris, J. Acoust. Soc. Am. 24, 750–755 (1952); J. O. Nordmark, J. Acoust. Soc. Am. 44, 1533–1540 (1968)]. Three estimates of a frequency difference limen were obtained from (1) the standard deviation of final settings in the method of adjustment; (2) the average of several reversals in an adaptive two-interval forced-choice procedure (two-up, one-down); and (3) the 76% point of a two-interval forced-choice procedure using constant stimuli. The 1000-Hz difference limen was estimated for the same subjects using each of the three procedures. The two forced-choice procedures yielded very similar limens. The limen estimated from the adjustment method correlated poorly with either of the others estimates and was lower by about a factor of two for five of the six subjects. [This research was supported by the National Institutes of Health.]
Fundamental pitch discrimination for monotic and dichotic two-tone complexes
Authors: Cudahy E.
Published: October 2005

Pitch discrimination for the fundamental frequency of a harmonic two-tone complex was investigated. The stimuli were either monotic, with both tones presented to a single ear, or dichotic, with one tone presented to each ear. An up—down two-alternative forced-choice procedure was employed. In each block of trials, seven differences in fundamental frequency around a fundamental frequency of 275 Hz were tested. The procedure was designed to minimize the pitch discrimination cue arising from the partials. The difference in fundamental frequency necessary for 75% correct discrimination (defined as Δf0) was measured as a function of the harmonic number (5–9) and duration (15–250 msec) of the complexes. Two general trends emerged from these data. First, as the duration of the complex tone decreased below 250 msec, performance deteriorated. The rank order of the Δf0's correlated well with duration, but the data were not characterized by a simple reciprocal relationship between Δf0 and stimulus duration. Second, except at the shortest duration tested, discriminability in the dichotic condition was less sensitive than that for the monotic condition. These results are in qualitative agreement with expectations of the pitch saliency of complex tones. [This research was supported by a National Institutes of Health research grant awarded to ASU.]
Note on periodicity pitch
Authors: Goldstein Moise H.
Published: October 2005

Pitch matching experiments were designed to test a recent theory for the pitch of complex tones [J. L. Goldstein, J. Acoust. Soc. Am. 54, 1496–1516 (1973); A. J. M. Houtsma and J. L. Goldstein, J. Acoust. Soc. Am. 51, 520–529 (1972)]. All subjects had at least eight years of musical training. One-half-second presentations of two pulse-train signals of moderate intensity were alternated. The experimenter set the pulse rate of signal “A” before each trial. The subject adjusted the pulse rate of signal “B,” ending the trial by indicating a pitch match. Acoustic stimulation was by earphones. The “B” signs was binaural; the “A” signal was dichotic. Two types of pulse trains were used: (i) periodic condensation pulses, and (ii) alternating condensation and rarefaction pulses. Signal “B” ha type i trains; their rate was rB pulses/sec. Signal “A” had type i trains to the right ear and type ii trains to the left ear. Pulses in the two ears were synchronous and had rate rA pulses/sec. Values of rA of 150, 200, 300, 400, 600, and 800 pps were used. For the rates of 200 pps and 150 pps, over 80 of the judgments yielded rB/rA ≃ 1. For rates of 400 pps and higher over 80% of the judgments yielded rB/rA ≃ 1/2. The theory of J. L. Goldstein predicts rB/rA ≃ 1/2 at all rates.
Composite acoustic media—alias fluid-saturated rocks
Authors: White J. E.
Published: October 2005

Geoacoustics, the application of acoustical theory and techniques to wave propagation in the earth, is centrally involved in two current developments in earthquake seismology and geophysical prospecting. The same theory which describes sound absorption by acoustical panels also describes wave propagation in fluid-saturated rocks. The effect of fluid on the speeds of shear and compressional waves in rocks may soon provide reliable forecasts of imminent earthquakes. Because of the profound effects of gas saturation, compared to liquid saturation, gas reservoirs can be mapped directly by seismic reflection profiling. Both of these significant developments are covered by a theory which shows how speeds and density depend on static stresses as well as on the intrinsic properties of the fluid and of the skeleton. When gas saturation occurs in discrete pockets or in thin layers, substantial dispersion of compressional waves is indicated by the theory, with attenuation coefficients 10 to 30 times larger than normal. Shear waves are not so strongly affected by fluid saturation. This aspect of geoacoustics applies also to evaluation of water resources and to engineering properties of soils.
Acoustic correlates of /ə/, /ɪ/, and /smcapi-/, in reduced stress position
Authors: Oshika B. T.
Published: October 2005

A transcription of four minutes of continuous speech from one male speaker included conventions for marking, in reduced stress position, the vowels /ə/, /ɪ/, or /smcapi-/, or choices between any two of these vowels when transcribers did not agree on vowel quality. The speech was digitized bandlimited at 5000 Hz and sampled at 10 000 Hz. Each of the (transcribed) reduced vowels was located manually by inspection of a time-synchronized plot of the waveform, spectral peaks, and rms. Formant parameters, derived from the inverse filter method of linear prediction, were extracted from four consecutive spectral samples representing 29.6 msec of the steady state of each vowel. Formant values for the reduced vowels were then plotted in the F1−F2 space, and distributions within that space were compared with perceived vowel choices. Some acoustic cues related to transcription choices are presented. [This research was supported by the Office of Naval Research under contract N00014-73-C-0221 and by the Air Force Office of Scientific Research under contract F44620-74-C-0034.]
Another look at the problem of the energy redistribution of a Gaussian ultrasonic beam at a liquid-solid interface
Authors: Adler Laszlo , Breazeale M. A. , Scott Gerald W.
Published: October 2005

The experimental observation that a Gaussian ultrasonic beam incident at the Rayleigh angle onto a liquid-solid interface distributes itself into two or more beams after reflection was reported earlier [Breazeale, Adler, and Flax, J. Acoust. Sec. Am. 56, 866 (1974)]. A theoretical analysis of the problem based on a modified version of Brekhovskikh's theory gave fair agreement between theory and experiment for the nonspecularly reflected beam. Another theoretical approach to this problem by Bertoni and Tamir [Appl. Phys. 2, 157 {1973)] gives expressions for both the specularly and the nonspecularly reflected amplitudes which have been observed experimentally by Neubauer. With the assumption that both transmitter and receiver are at the interface, this theory describes the reflected beams in terms of complementary error functions with real arguments. Including the appropriate distance between the transmitter and receiver and the interface causes the argument of the complementary error function to become complex. With this modification, the amplitude distribution of the nonspecularly reflected beam shows such structures as we have observed experimentally, including secondary beams beyond the principal “displaced” beam. [Research supported by U. S. Office of Naval Research.]
Vowel quality discrimination with dichotic and asynchronous formant excitation
Authors: Paul D. J. , Haggard M. P.
Published: October 2005

Human perception of vowel sounds and transitions may depend not solely upon picking peaks out of a time-averaged fine spectrum but also upon gross spectral slopes and formant interactions. Interactions could occur in the time domain as well. Discrimination of small changes in F1, F2, and F1 + F2 in a low back vowel was investigated to seek such formant interaction. Pairs of brief vowels were presented for same/different judgment with (1) normal series formant connection, binaurally, (2) F1 and F2 separated dichotically, and (3) F2 excitation delayed with respect to F1 by approximately a half fundamental period, then mixed and presented binaurally. Unbiased measures showed differences in levels of discrimination, with (1) better than (2) better than (3). Thus, at least for formants close in frequency and of low to mid-frequency, both spectral and waveform interactions of formants contribute to vowel quality in ways not covered by combination of parameters representing individual peak positions.
Vowel information conveyed by consonant transitions
Authors: Raphael Lawrence J. , Dorman M. F. , Liberman A. M.
Published: October 2005

It is well established that information specifying place and manner of articulation for stop consonants is conveyed by the transitions of the vocalic segment. The purpose of this study was to determine whether these transitions also convey information about vocalic duration. Accordingly, four series of synthetic stimuli were generated: three of the series consisted of CVC syllables in which the initial C transitions were set at durations of 30, 60, and 90 msec; a fourth series consisted of VC syllables. In all four series the duration of the steady-state portion of the vowel was varied from 10 to 190 msec in 10-msec steps. The final consonant was synthesized with transitions appropriate for an unreleased /d/. Listeners were asked to identify the final consonant as voiced or voiceless (/t/ or /d/). For vowel steady states of equal duration, the addition of initial consonant transitions caused a shift in the perceptual boundary between the voiced and voiceless categories. This outcome suggests how a portion of the initial “consonant” transition is used by the listener in computation of “vowel” duration, at least for the purpose of cueing the voicing distinction in final position.
On accounting for the poor recognition of isolated vowels
Authors: Shankweiler D. , Strange W. , Verbrugge R.
Published: October 2005

Earlier studies have shown that vowels spoken in isolation tend to be poorly perceived, even when they are produced by phonetically trained talkers. Listeners, however, generally make remarkably few errors in identification of vowels in CVC environment, even when each syllable is uttered by a different talker. Sets of nine American English vowels were spoken by a panel of talkers: in isolation and in a /p-p/ environment. Measurements of the first three formant frequencies were obtained from spectrograms. Listening tests were made up by randomizing talkers and tokens, and these were presented to phonetically naive listeners. Percent recognition of the intended vowel (average over vowels) was 83% for the /p-p/ condition and 58% for the isolated condition. When the formant frequencies of each talker's isolated and medial vowels are compared, the values are found to be highly similar. Another explanation must be sought for the perceptual difficulty of isolated steady-state vowels.
Speech perception by the chinchilla: phonetic boundaries for synthetic VOT stimuli
Authors: Kuhl Particia K. , Miller James D.
Published: October 2005

We recently reported that the phonetic boundary for the Lisker-Abramson synthetic /da-ta/ stimuli was identical for the chinchilla and English-speaking adults. We have now tested the same animals on VOT stimuli with labial, /ba-pa/, and velar, /ga-ka/, places of articulation. For each VOT series, the animals were trained to respond differently to synthetic stimuli with VOTs of 0 msec and + 80 msec. In subsequent sessions, these “endpoint” stimuli were presented on half of the trials. while the stimuli with VOTs between 0 and + 80 msec were presented on the other half of the trials. During “endpoint” trials, all relevant feedback was maintained, but when all other stimuli were presented, feedback was arranged to tell the animal he was always “right,” no matter what he did. The chinchilla shifts his boundary for labial, alveolar, and velar stimuli as does the English-speaking adult. These results suggest that the location of the phonetic boundary for these stimuli can be accounted for by their acoustic structure and general psychoacoustic processing. [Supported by NIH Grant NS 03856 to CID.]
On pushing the voice-onset-time (VOT) boundary about
Authors: Lisker Leig , Liberman Alvin M. , Dechowitz David , Erickson Donna M.
Published: October 2005

There is voluminous evidence that homorganic stop consonants are distinguishable on the basis of voice onset time relative to their supraglottal articulation. For initial stops a convenient acoustic reference point is the onset of the release burst, and VOT has been defined as the interval between this point and onset of glottal signal. VOT boundary values between voiced and voiceless initial stops of English have been established by spectrographic measurements of naturally produced isolated words and by perception testing of synthesized CV syllables. The close match between the two kinds of boundary values suggests that fairly natural values were chosen for the invariant features of the synthetic speech patterns tested. It is known, however, that certain of these affect voicing perception. New data from synthesis experiments show that VOT boundaries shift with changes in transition duration, that it is the first formant and not higher ones which are responsible, and that transition duration is constrained to values which differ for place of articulation. It is hypothesized that listeners evaluate VOT with respect to estimated rate of articulation.
Dichotic and diotic presentation of a click-on-sentence task
Authors: Onufrak J. A.
Published: October 2005

Twenty-four subjects were presented with 35 click-on-sentences both diotically (sentence and click both ears) and dichotically (sentence right ear and click left ear) and asked to locate the click in relation to the sentences. The click was always located in the middle steady-state portion of a vowel. The general categories of sentences recorded were syllabic stress variation in relation to click and click variation in relation to phrase boundaries. The results of this study indicated that (1) diotic presentation produced many more accurate responses than dichotic delivery, (2) the parameters stress and boundary each produced characteristic kinds of responses, (3) critical temporal measurements of individual sentences in immediate proximity with click placement were found to influence the kinds of responses, and (4) there is an overall tendency to estimate the click before its actual location. The accuracy of responses to the task is considered to reflect both the ability to rapidly change foci to the several aspects of the linguistic pattern and the resulting strategy an individual uses in accomplishing the task.
Categorical perception, auditory memory, and dichotic interference: a “same”—“different” reaction time study
Authors: Repp Bruno H.
Published: October 2005

A “same”—“different” reaction time study was conducted in which stimuli from a voice onset time continuum were presented dichotically at seven different stimulus onset asynchronies (0–3.3 sec). There were two kinds of instructions: “phonetic match” (same or different category?) and “acoustic match” (same or different stimulus?). The study was aimed at the following questions: (a) Can the effect of acoustic differences on reaction time [Pisoni and Tash, Percept. Psychophys. 15, 285 (1974)] be replicated? (b) Does this effect decrease with temporal separation of the stimuli? (c) Do pretraining and “acoustic match” instructions lead to improved discrimination in this paradigm [cf. Pisoni and Lazarus, J. Acoust. Soc. Am. 55, 328 (1974)]? (d) Do they increase the Pisoni-Tash effect? (e) Is within-category discrimination greatly improved and as good as between-category discrimination with simultaneous dichotic syllables? (f) Are incorrect “different” responses under dichotic interference (at short time lags) related to distance of the stimuli from the category boundary [cf. Repp, J. Acoust. Soc. Am. 56, S53 (1974)]. Preliminary analysis suggests these answers: (a) yes; (b) no; (c) no; (d) yes; (e) yes and no; (f) no? Final results and their implications are discussed.
Feature analyzers for the phonetic dimension stop vs continuant
Authors: Diehl Randy L.
Published: October 2005

Perception of the phonetic dimension stop vs continuant was studied by means of a selective adaptation procedure. Subjects first identified a series of synthetic consonant-vowel syllables which varied in duration of formant transitions: they were perceived as either /ba/ or /wa/. After the initial identification test, an adapting stimulus was presented repeatedly, and then the subjects again identified the original test series. Adapting with a stop (either /ba/ or /da/) led to a decrease in the number of test stimuli identified as /ba/, whereas adapting with the continuant sound /wa/ led to an increase in the number of /ba/ identifications. A reduction in the number of /ba/ identifications occurred even when a nonspeech stop sound (string pluck) was used as the adapting stimulus. Because the acoustic information specifying stop quality for this nonspeech stimulus was entirely different from that specifying stop quality for the test stimuli, it was concluded that the “stop detector” operates at a more abstract level than that of either a simple acoustic or phonetic analysis.
Development of single-cell binaural interaction in the inferior colliculus of the rat
Authors: Silverman M. S. , Clopton B. M. , Flammino F.
Published: October 2005

The importance of early binaural stimulation for the expression of binaural interaction in the rat inferior colliculus was investigated following monaural or binaural sound deprivation. Stimulus deprivation was achieved by unilateral or bilateral ligation of the external auditory meatuses of rats at ten days or one month of age. At three months of age the ligatures were removed, and responses of single units in the inferior colliculus were recorded while click stimuli were presented binaurally. Interaural intensity differences were varied over a range of 40 dB in 10-dB steps. Those rats monaurally deprived from ten days of age showed a marked loss of binaural interaction as manifested in an absence of ipsilateral inhibition of unit activity. Animals monaurally deprived from one month of age, or those binaurally deprived from ten days or one month, exhibited normal binaural interaction. The results indicate that the development of binaural interaction at the inferior colliculus of the rat is dependent on symmetrical binaural stimulation during the first postnatal month in the rat.
Low-frequency (1 kHz) sound absorption in sea water as measured in the laboratory using a spherical resonator
Authors: Simmons V. P. , Fisher F. H.
Published: October 2005

Laboratory measurements using a 200-liter spherical glass resonator generally confirm the existence of increased sound absorption below 1 kHz as previously reported from at sea data. The increased absorption is slightly less than the ten times increase that the at-sea data would indicate, and the absorption is due to the presence of boric acid in sea water. The dependence of the absorption on pH and boric acid concentration indicate a bimolecular chemical relaxation as the primary cause. Data related to temperature, concentration, and pH dependence of the absorption are presented. The measured effects on the reaction of all the other chemical constituents in Lyman and Fleming sea water are discussed. [This paper represents results of research sponsored by the Office of Naval Research.]
Reaction kinetics of the apparent boric-acid-related low-frequency (1 kHz) relaxation in sea water
Authors: Simmons V. P. , Fisher F. H. , Levison Stuart A.
Published: October 2005

Previous studies using the temperature-jump equipment have confirmed the existence of a chemical relaxation in a boric acid solution of sea water concentration in a NaCl medium. The chemical relaxation time is generally consistent with the 1-kHz relaxation hypothesized from the open ocean data previously presented by several authors. New data indicate the importance of the concentration of B, Mg, Ca, and HCO3 on the boric acid relaxation time, bimolecular reaction process, and concentration consistent with the observed data. [This paper represents results of research sponsored by the Office of Naval Research.]