bluuebunny/crossref_metadata_2025 huggingface dataset:
The perception of /v̥/, x, ʕ ħ/ and /š, s/
Authors: May Janet
Published: October 2005

The perception of the voiced and voiceless velar and pharyngeal fricatives/v̥, x, ʕ, ħ/ and of /š, s/ in Colloquial Egyptian Arabic was examined to determine if the presence of the first two or three formants in /v̥, x, ʕ, ħ/ results in continuous perception, in contrast to an expected categorical perception of /š, s/ which lack these formants. Three 12-step continua containing /ə/-c-/ə/ nonsense words were synthesized. For the/š-s/ continuum, the center of a high-frequency resonance was varied in equal steps. For the /x-ħ/ and /v̥-ʕ/ continua F1 was varied. Eight native speakers were asked to identify 16 tokens of each stimulus and discriminate each two-step stimulus pair 24 times in a 41AX discrimination task. While /v̥-ʕ/ showed continuous or less categorical perception than /š-s/, /x-ħ/ was perceived somewhat categorically. This may be explained by the fact that since /x/ and /ħ/are voiceless, they may contain less information about the lower formants than do their voiced counterparts /v̥/ and /ʕ/. [This work was supported by NICHD grant HD01994 to Haskins Laboratories.]
Speechwave properties influencing segmental integration
Authors: Dechovitz D. R.
Published: October 2005

The fricative-affricate contrast is signaled by a set of diverse acoustic features. The present research proposed to identify properties of the speechwave constraining the stretch of signal over which these features are integrated. In addition, the possibility was investigated that these properties may also define the constraints which close off processing units for perceivers. To these ends, the role of silence in distinguishing fricative from affricate was assessed at various syntactic boundaries and in speech samples produced with various degrees of articulatory continuity. Previous results suggested that information specifying the temporal period of an utterance delimits coherent units and may even define units over multiple talkers [D. R. Dechovitz and B. Rakerd, J. Acoust. Soc. Am. 64, S18(A) (1978)]. The present data suggest further that this information is not necessarily correlated with the acoustic structure signalling major constituent boundaries. [Work supported by NIH, BRS Grant RR05596.]
The use of duplex perception to study silence as a cue for stop consonants
Authors: Isenberg D. , Liberman A. M.
Published: October 2005

Removal of the silent closure interval from /spa/ or /sta/ typically results in the perception of /sa/. To determine whether this phenomenon is an instance of phonetic (as distinct from auditory) perception, we used the method of duplex perception. This has the advantage that a single stimulus pattern yields speech and nonspeech percepts simultaneously [D. Isenberg and A. M. Liberman, J. Acoust. Soc. Am. 64, S20(A) (1978)]. Applying this method to the synthetic syllables /spa/ and /sta/, we separated the F2-F3 transitions (which alone distinguished the syllables} from the base (the pattern common to the two syllables). When the base is presented in isolation it sounds like (s-a/ or /as/ depending on whether or not a silent interval is present. The transitions alone sound like nonspeech chirps. When the base and the transitions are presented dichotically, listeners simultaneously hear a syllable and a nonspeech chirp. In the ear which receives the base, they hear /spa/ or /sta/ when a silent interval is present, contingent on the transition in the other ear; when the silent interval is absent, /sa/ is heard with either transition. In contrast, the nonspeech chirps, heard in the ear which receives the transitions, do not change with the presence or absence of the silent interval. Given that the speech changes while the chirp does not, the effect of silence in cueing the stops can hardly be interpreted as an instance of auditory interaction: it can more plausibly be seen as a result of distinctively phonetic processes. [Work supported by NINCDS and NICHD.]
Some perceptual dependencies between vowel color and pitch
Authors: Carrell T. D. , Smith L. B.
Published: October 2005

How to acoustic dimensions combine in speech perception? Wood [C. C. Wood, J.E.P.: HP & P, 104, 3–20 (1975)] suggested that information specifying consonants is dependent on the earlier processing of pitch because pitch judgments are unaffected by consonant variation whereas consonant judgments are slower when pitch varies. Is vowel information also dependent on the prior processing of pitch? In contrast to the results obtained with consonants, Kuhl [P. K. Kuhl and J. D. Miller, J. Acoust. Soc. Am. Suppl. 1, 58 (1975) and P. K. Kuhl, J. Acoust. Soc. Am. Suppl. 1, 60 (1976)] reported that infants respond selectively to vowel color when pitch varies but not to pitch when vowel varies. In this study we examined adults' judgments of vowel color and pitch in a reaction time task. Subjects classified stimuli as /i/ or /ɛ/, or as high or low pitch. Consistent with Kuhl's results, vowel judgments were unaffected by pitch variation whereas pitch judgments were slower when the vowel varied. However, this result was obtained only when the pitch difference was small (15 Hz). With a larger pitch difference (75 Hz), no interference between pitch and vowel was observed. The asymetric interference found in the first case, then, was likely due to the greater discriminability of vowel color over pitch. Thus, conclusions about perceptual dependencies in speech perception must be made cautiously as the effects may be due to the discriminability of the specific values on the dimensions under study. [Supported by NIMH.]
Context-determined effects of varying closure duration
Authors: Lisker L. , Price P.
Published: October 2005

Much evidence exists to show that /p/ is produced with longer closure than /b/, when they occur in words like rabid and rapid. If /b/ closures are silenced and lengthened, listeners tend to report /p/. There is the temptation to draw from this the generalization that closure duration serves to distinguish /ptk/ from /bdg/, i.e., that it is a cue to voicing. There is a context, however, in which the manipulation of closure duration has a rather different phonetic outcome; where in fact a longer duration is reported as /d/ and a shorter as /t/. The word pair center-sender, where the medial consonants are described for many varieties of American English as a nasalized flap in the one case and as a sequence of nasal plus stop in the other, is such a context: shortening the oral voiced closure of sender yields center when the closure is reduced to 40 ms or less. [The support of the National Institute of Child Health and Human Development is gratefully acknowledged.]
The perceptual equivalence of trading-relation cues
Authors: Fitch H. L. , Halwes T. , Erickson D. , Liberman A. M.
Published: October 2005

At an earlier meeting, we presented results of a study of the effects on phonetic identification of orthogonal variation in a temporal cue and a spectral cue that are the common acoustic products of a single phonetically significant act. Within limits, contrasting phonetic identifications could be obtained by varying either one, and the presence of an extra amount of one could compensate for the absence of the other (thus a trading relation was established). We suggested ways of pairing the cues in syllables for discrimination judgements to test whether the implied perceptual equivalence was genuine. This paper reports the results of such a test. The appropriate pairs did prove hard to discriminate. We propose that the equivalence thus demonstrated is due to a perceptual system specialized to take account of the common origin of the two cues. [Work supported by NICHD.]
Physiological and psychophysical studies of amplitude modulation detection by the goldfish
Authors: Fay R. R.
Published: October 2005

Goldfish were classically conditioned to suppress respiration during a brief period of sinusoidal amplitude modulation (SAM) impressed upon a continuous 800 Hz, 35 dB SL carrier signal. The just-detectable depth of modulation (m) was measured as a function of modulation frequency (fm) between 2.5 and 400 Hz, using a modified method of limits. The sensitivity of modulation detection grows with frequency at about 3 dB/octave up to about 200 Hz where fishes could detect modulation at m = 0.004. This corresponds to a peak-to-trough intensity difference of about 0.07 dB. Similar experiments were performed on single saccular neurons of the goldfish. Modulation period histograms were obtained, and the degree of phase locking and the phase angle of the response were measured as functions of m and fm. Neurons generally showed bandpass frequency response characteristics with best modulation frequencies occurring between 20–300 Hz, and at sensitivities (based on phase-locking criteria) comparable to those measured behaviorally. Each neuron exhibited a characteristic delay between corresponding points on the stimulus envelope and the period histogram. This delay ranges between 2.5–10 ms, and is inversely proportional to the neuron's best modulalion frequency. The extremely high behavioral sensitivity to amplitude modulation appears to depend upon mechanisms leading to temporal contour enhancement in the neural response, and not to spectral processing. [Work supported by the NSF.]
Recovery from short-term adaptation in auditory nerve fibers of the leopard frog
Authors: Megela A. L. , Capranica R. R.
Published: October 2005

The effects of an adapting tone (750 ms duration) on subsequent responses to a brief (200 ms) test tone were examined in single auditory nerve fibers of the leopard frog, Rana pipiens. Both tones were set at each fiber's best excitatory frequency, with intensities from 10 to 30 dB above threshold. Response magnitude to the test tone decreased as the interval between the adapting and test tones was shortened. Furthermore, the degree of response decrement and recovery was related to the firing pattern of each unit as determined from PST histograms. “Tonic” units exhibited greater relative decrement and longer time course of recovery than did “phasic” units. High-frequency-sensitive fibers from the basilar papilla all showed similar degrees of adaptation. Within the amphibian papilla, the degree of adaptation seemed to be related to best excitatory frequency: mid-frequency-sensitive fibers tended to show greater adaptation than did low-frequency-sensitive fibers. [Supported by NSF and NIH.]
Forward masking of click responses in auditory nerve fiber as a function of CF
Authors: Dolan D. F. , Teas D. C. , Hill R. C. , Walton J. P.
Published: October 2005

Discharges of auditory nerve fibers to broadband clicks were masked with tone bursts (rise time, 1 ms; duration, 30 ms) of 4,8, or 13 kHz. The tone burst preceded the click by 10 ms, thus the click response was subjected to “forward masking.” Click intensity was set 30 dB above the intensity which produced a just detectable N1 averaged response (256 epochs). After determining CF for each fiber, a PST histogram of the unit's response to the click at the standard intensity was taken. Tone burst frequency was then set at 4, 8, or 13 kHz and PST histograms to the click were recorded as the intensity of the tone bursts was increased in 10 dB steps. The reduction in click responses by each forward masker was measured for units distributed over a range of CF for constant masker intensities. The discharges of units with CFs near the masker frequency are reduced by the greatest amount, those from units with CFs below masker frequency may show an increase in discharges to the click. [Supported by NSF, No. BNS-77-16907.]
Effects of time on decremental responses of single auditory-nerve fibers
Authors: Brachman M. L. , Smith R. L. , Frisina R. D.
Published: October 2005

Stimuli consisted of CF tone bursts with superimposed increments or decrements in sound intensity. The intensity changes were applied at various time delays from tone onset and the resulting changes in response firing rate were computed from PST histograms. Consistent with previous results [R. L. Smith, J. Acoust. Soc. Am. 65, 166–178 (1979)], the change in response was independent of the time delay to the change in intensity, as long as firing rates were averaged over time windows exceeding 10 ms. When the same data was analyzed using windows of less than 2 ms, the initial increment in response caused by an increment in intensity remained independent of time delay. In contrast, the initial decrement in response caused by a decrement in intensity decreased with increasing time delay and appeared to be closely related to the amount of adaptation preceding the decrement. Similar decreases were observed in the response modulation produced by amplitude-modulated stimuli. Thus, while incremental and decremental responses are basically additive, the initial portion of the decremental response appears to reflect a qualitatively different process.
Discharge synchronization in auditory nerve and AVCN neurons
Authors: McGee JoAnn , Walsh Edward J. , Javel Eric
Published: October 2005

At suprathreshold intensities, all auditory nerve fibers and many anteroventral cochlear nucleus (AVCN) neurons exhibit discharge synchronization or phase locking to signal frequencies less than 4–5 kHz. However, the relationships between synchronization and discharge rate have not been fully described. In the present study, discharges of single auditory nerve and AVCN neurons were recorded in anesthetized cats. Signals consisted of low- and moderate-frequency pure tones. Neuronal response patterns were analyzed by techniques employing discharge rate and by Fourier transforms of period histograms synchronized to the signal frequency. A criterion number of discharges (usually in excess of 1000 spikes) was collected at each intensity in order to reduce sampling biases. In both spontaneously active and inactive neurons, the threshold for detectable phase locking is 12–18 dB below the threshold for increases in discharging rate. Once the synchronization threshold is exceeded, phase locking continues to increase with increasing signal intensity. Asymptotic phase locking is achieved prior to maximal discharge rate, but the range over which phase locking increases is somewhat greater than the range over which discharge rate increases. Mean discharge phase does not vary appreciably at intensities above the phase-locking threshold. Auditory nerve and AVCN neurons behave similarly.
Responses of cat inferior collicular neurons to interaural delays and binaural beats: A comparison of techniques
Authors: Kuwada S. , Yin T. C. T. , Wickesberg R. , Buunen Theo
Published: October 2005

Many low-frequency inferior collicular neurons respond cyclically as a function of interaural delay. Since the interval between peaks of this cyclic function equals the period of the stimulating frequency, then these neurons must be sensitive to phase differences created by varying the interaural delay. Binaural beat stimuli also create a changing phase difference and thus should yield similar response patterns to those found to varying interaural delay. This is in fact the case. Almost all neurons which respond cyclically to interaural delays will also respond similarly to the beat frequency stimulus. Furthermore, the maximal discharge for both types of stimuli occurs at the same phase difference. We have studied neurons which can faithfully follow beat frequencies as high as 70 Hz. The use of binaural beats has the added advantage over interaural delay stimuli in that it provides the opportunity to study the dynamic aspects of a simulated sound source in space, i.e., the responses of neurons to moving sound in different directions and different velocities. In fact, we have studied neurons that respond only when the simulated sound source (via beat frequency) is moving in a particular direction and others that respond maximally to a particular velocity.
Psychophysical tuning functions: Influence of probe duration
Authors: Durrant J. D. , Walter M.
Published: October 2005

Recent research has demonstrated that a great deal of frequency specific information is available in evoked responses from the eighth nerve and the brain stem. In electrocochleography and brain-stem evoked response audiometry very short tone bursts or pips (i.e., 2 ms duration with 1 ms rise/fall) are used to avoid artifacts. We questioned the extent to which frequency selectivity might be degraded by the use of such short and transient stimuli since physically they have substantially broader spectra than pure tones and subjectively they lack tonality. An automatic tracking procedure was used to obtain tuning functions from human subjects via a tone-on-tone masking paradigm. The results suggest that there is little loss in the apparent frequency selectivity with decreasing duration of the probe stimuli as long as the intensity of the tone pip is kept relatively low. Due to the threshold power integration phenomenon this means that sharp tuning may be seen only at sensation levels less than 10 dB for a pip of, say, 2 ms. The tips of the tuning functions seem to disappear at a set sound pressure level of the probe, regardless of duration. The implications for evoked response audiometry will be discussed. At this juncture it appears that, at least under certain conditions, responses elicited by even very brief tone bursts reflect an impressive degree of frequency specificity.
Click-evoked brainstem responses recorded nearfield and farfield in waking guinea pigs
Authors: Mikaelian D. , Wilpizeski C. , Balshi J. , Doghramji K.
Published: October 2005

Hartley strain guinea pigs (500–700 g in body weight) were provided with permanent unilateral recording depth electrodes having tips localized in the region of the auditory tubercle and with screw-type electrodes in contact with the dural surface of the posterior pole of the cerebrum. Under waking conditions, nearfield and farfield click-evoked responses (early components of BSER) were processed by a summing computer, and waveforms were analyzed in terms of peak amplitudes and latencies. Farfield evoked responses were recorded from a subsidiary group of guinea pigs having surface and needle scalp electrodes. Waveform characteristics of the farfield response differed from those of the human, Jewett-type response as expected on the basis of differences in anatomical scale. Although basic characteristics of waveforms recorded from different electrode locations were similar, absolute and relative amplitudes, phase and latencies of some peaks varied with recording site. Early components of the nearfield responses exhibited considerable intersubject variability and often did not resemble farfield waveforms.
Interpretation of features of radiation from locally excited, periodically supported plates
Authors: Berkman E. F. , Smith P. W. , Haberman R.
Published: October 2005

A precise closed form analysis is now available for calculating the radiation into a fluid from a periodically supported infinite plate excited at a point or on a line. This technique fully includes the effects of fluid loading and all mutual interactions between supports. Characteristics of the radiation field are examined by example, and some physical interpretations of significant features are offered. Specifically, prominent peaks in the frequency response, which have been attributed to structural resonances, are shown rather to be caused by coherent radiation from the regular array of supports.
Flow-induced noise in merchant ship broadband source levels
Authors: Wright Evan B.
Published: October 2005

Source level spectra for 14 large merchant ships have been measured with hydrophones at about 400 m from the ships' tracks. The measured broadband levels tend to be fairly constant from 20 or 30 Hz down to 4 or 5 Hz, instead of decreasing. A possible cause of these high measured low-frequency levels is flow-induced noise radiated from the turbulent boundary layer on the ship's hull [E. A. Vecchio and C. A. Wiley, J. Acoust. Soc. Am. 53, 596–601(1975)]. This paper presents results of calculating the radiated flow-induced noise, as received at the experimental ranges. The smooth-plate expressions for boundary layer thickness and source spectral density have been modified to conform to typical hull roughness. The computed levels, above 5 Hz, are generally less than 10 dB from the measured received levels, suggesting that flow-induced noise is an important component of merchant ship radiated noise from about 5 to 20 Hz.
Hearing levels of adults 25–74 years of age in the general population by sex and race: United States, 1971–1975 and 1960–1962
Authors: Roberts Jean
Published: October 2005

Nationally representative hearing level data for the United States adult population have been obtained in two recent surveys—the Health and Nutrition Examination Survey of 1971–1975 and the Health Examination Survey of 1960–1962. In each of these cross-sectional national surveys, a probability sample was selected for examination. The carefully controlled pure-tone audiometric testing, done in an acoustically treated environment and with testing equipment somewhat improved in the more recent survey, was part of the standardized examination given in each. Hearing level data for the general adult population from the National Health and Nutrition Examination Survey of 1971–1975 are analyzed with respect to presently existing (at that time) age, sex, and racial differences in air-conduction levels. Comparisons are made with hearing levels for the general population from the National Health Examination Survey of 1960–1962 for possible implications that these findings may have for noise abatement and control and other hearing conservation programs. While broad regional comparisons are also possible, the survey samples are too small and the sample frame designed so that only broadly based changes in hearing sensitivity within the general population would generally be detected.
Nonlinear propagation effects in aircraft noise
Authors: Crighton D. G.
Published: October 2005

Nonlinear effects have recently been shown to play an important role in the propagation of jet noise over the large distances involved in the noise certification process provided the acoustic field at moderate distances contains a sufficient level of low-frequency energy. These effects invalidate model to engine scaling laws, may cause misinterpretations of source mechanisms and may have contaminated some of the real-engine data used in standard prediction schemes. This paper presents a simple analytical description of the nonlinear evolution of broadband noise signals and the consequent enrichment of high frequencies. The model is sufficiently simple to permit incorporation of atmospheric attenuation, spherical spreading, and nonuniformity of the directivity at moderate distances, and can be used also in inverse fashion to obtain the moderate distance spectrum from that found at large distances.
Finite amplitude two-dimensional waves in a rectangular duct induced by arbitrary periodic excitation
Authors: Ginsberg J. H.
Published: October 2005

The nonlinear two-dimensional acoustic waves that occur within a rectangular duct of semi-infinite length as the result of periodic excitation are determined by an asymptotic method. A regular perturbation expansion is employed to obtain the velocity potential as a solution of a nonlinear wave equation. Uniformly valid expressions for the particle velocity components and pressure are then derived with the aid of a coordinate straining transformation that features both spatial coordinates. The response is found to be formed from the linear superposition of nondispersive groups of propagating nonlinear waves, each of which corresponds in linear theory to a fundamental wave and all overtones having the same phase speed, together with exponentially decaying standing waves resulting from excitations below the cutoff frequency. The distortion of each nondispersive group is found to be the result of self-refraction, wherein the rays and wavefronts are deviated in the direction of the particle velocity. Typical spatial profiles and temporal responses for one nondispersive group are discussed in an example.
Standardization of a test of speech perception in noise (SPIN)
Authors: Bilger R. C. , Rzcezkowski C. , Nuetzel I. , Rabinowitz W. M.
Published: October 2005

All ten forms of the SPIN test [D. N. Kalikow, K. N. Stevens, and L. L. Elliott, J. Acoust. Soc. Am. 61, 1337–1351 (1977)] were presented to 128 listeners who had some sensorineural hearing loss. Speech materials were presented at a level calculated to correspond, approximately, to the loudness equivalent to 60 dB SPL for a normal-hearing listener, and the babble noise was set 8 dB lower (S/B = +8 dB). Half of the subjects heard the test through earphones and half via loudspeaker; half were tested in a single session and half in two sessions. Statistical analysis of these results indicated that (a) transducer, (b) visits, and (c) order of testing had no influence on test scores. The average reliability coefficient was 0.906 for the high-probability items in a form and 0.848 for the low-probability items. The ten forms tested, however, do not constitute a set of equivalent forms; and it is difficult to identify a subset of equivalent forms, because of the large differences in difficulty among forms with respect to the low-probability sentences. [Work done under contract to NINCDS.]
Observations with a method of acoustic stimulus monitoring
Authors: Boston J. R. , Ainslie P. J.
Published: October 2005

The purpose of this study was to evaluate the utility of an electret microphone mounted on an carphone muff [R. H. Domnitz, “Headphone monitoring system for binaural experiments below 1 kHz,” J. Acoust. Soc. Am. 58, 510–511 (1975)1 to monitor stimulus waveform in auditory evoked potential studies. Click stimuli were used to provide a broadband stimulus, and intrasubject and intersubject variability in the stimulus waveform was examined. Stimulus waveforms obtained in a given subject are repeatable from session to session, although some care must be taken in placement of the earphone on the ear. Amplitude measurements are not as repeatable. Significant intersubject variability in the recorded stimulus waveform is observed, and it is concluded that this variability is due to differences in transducer output on different ears rather than to differences related to the monitoring technique. The monitoring microphone can provide a reasonably reliable record of the acoustic waveform produced by the transducer, but amplitude measurements are not reliable. It is also noted that the microphone gives the stimulus waveform in the outer ear, not at the eardrum. [Work supported in part by a grant from NSF.]
Developmental changes in displacements of the malleus measured in neonatal hamsters by a capacitive probe
Authors: Relkin E. M. , Saunders J. C. , Bock G. R.
Published: October 2005

Displacements of the malleus were measured with a capacitive probe in neonatal hamsters between 16 and 75 days postpartum. After anesthesia, the tympanic ring and the auditory bulla were exposed. Small bore nylon tubing was used to ventilate the bulla to equalize middle-ear pressure to ambient pressure. The capacitive probe was positioned over the tip of the manubrium and calibrated in-vivo with an electromechanical vibrator. Tones between 0.5 and 30.0 kHz were applied in the free field. Sound level measurements were made on-line with a probe tube microphone. Displacement, extrapolated for 100 dB SPL, versus frequency curves show a low pass characteristic with a cutoff frequency near 9.0 kHz. The amplitude of displacement increased with age to a plateau at all frequencies. The slope of the high frequency rolloff was found to decrease with age. Comparisons of inverse velocity curves with cochlear nucleus evoked response threshold curves were made to determine the effects of middle-ear ontogeny on the development of auditory thresholds. [Supported in part by the NSF and the Deafness Research Foundation.]
Versatile High-Speed One-Third-Octave Band Analyzer
Authors: Kundert W. R. , Partridge G. R.
Published: October 2005

When large numbers of data must be processed or when an analysis must be completed rapidly or “on line,” parallel operation is essential. An additional gain in speed is realized by handling and/or reducing the spectral information digitally. A new high-speed analyzer has been developed. Using a digital rms detection scheme and calibrated gain controls in the filter channels, the accuracy and dynamic range limitations inherent in conventional analyzers are overcome. A 70-dB basic dynamic range capability can be extended to an effective dynamic range of 95 dB by “prewhitening” with the calibrated gain controls. The detector has ideal characteristics in that it is totally insensitive to signal waveform. The digital approach also makes practical a wide range of integration periods. The analyzer has been designed to allow great flexibility in operation with accessory equipment. It is fully programmable and intended for use in computer-controlled systems. In addition to its control function, a computer can serve to rapidly store data from the analyzer, determine ratings, and make comparisons.
Dynamical Theory of String Excitation by Bowing
Authors: Lazarus Hans
Published: October 2005

The kinematics of the bowed string have already been observed and mathematically described by H. von Helmholtz. For the present investigation we need to know the energy supply at the location of bowing and the energy loss in the vibrating system. A self-excited mechanism is used to create the energy supply between bow and string. To analyze string excitation at that point investigations were made of: characteristic of friction between bow and string; influence of the normal force between string and bow on the steady vibration; longitudinal impedance of the bow hair; influence of the eccentric excitation on the string, which also introduces torsional waves. The steady state of the bowed string was calculated with regard to the characteristic of the friction force and a complex impedance at the end of the string corresponding to the bridge, taking into account the modes of the body and all energy losses. Results explain the influence of the normal force between bow and string on the steady vibration. Results were confirmed by an electromechanical model of a bowed string.
Thermoelastic waves generated by laser beams of low power
Authors: Kohanzadeh Y. , Whinnery J. R. , Carroll M. M.
Published: October 2005

A modulated or chopped beam from an argon ion laser, with CW power at the 1−W level, is used to generate thermoelastic waves in several liquids. The ceramic cylinder surrounding the liquids is the transducer for the acoustic waves. Output signal is measured as a function of frequency, with different laser powers and different amounts of absorption in the liquids. The analysis makes use of thermoelastic potentials in the liquid and in the ceramic cylinder, with appropriate continuity conditions between the two regions, and predicts results in good agreement with those measured. Conversion efficiency from laser power to acoustic power is extremely low at this power level, but increases directly with the laser power. Thus it is concluded that the acoustic wave generated by a modulated laser beam at the 1−W level propagating through sea water would only be detectable near the beam, but for a pulsed beam at the megawatt level, acoustic power might be detectable for several kilometers.

Subject Classification: 35.65.
A discrete−continuum theory for periodically layered composite materials
Authors: Chao T. , Lee P. C. Y.
Published: October 2005

A discrete−continuum theory for periodically layered composite materials is presented. Based on a two−term truncated power series expansion of the displacement field about the middle plane of each layer, two−dimensional equations of motion are obtained for the individual layers. After introducing appropriate continuity conditions at the interfaces between neighboring layers, the governing field equations for periodically layered media are derived in the form of a system of differential−difference equations. The accuracy of the theory is examined by applying it to the propagation of plane harmonic waves in an unbounded layered medium and comparing the results with those obtained from theory of elasticity. To illustrate the application of the theory, thickness−twist vibrations of laminated plates are studied. Numerical examples are included and comparison is made with exact solutions.

Subject Classification :40.24.
Asymptotic frequency spread in surface−scatter channels at large Rayleigh numbers
Authors: McDonald J. F. , Schultheiss P. M.
Published: October 2005

When monochromatic radiation is scattered by a randomly time−varying boundary, frequency spreading occurs. If the source is essentially onmidirectional a simple expression can be obtained for the spectrum of this frequency spread. For Rayleigh numbers above a relatively small minimum one generally finds that the bandwidth of this spreading spectrum varies with the first power of the Rayleigh number. It is, however, possible to devise not entirely unrealistic conditions under which the spread appears to vary with the square of the Rayleigh number.

Subject Classification: 60.20.
Some influences of subjective tones in monaural tone−on−tone masking
Authors: Clack T. Dean
Published: October 2005

The influences of subjective phenomena upon measurements of monaural tone−on−tone masking not only effects interpretations of sensitivity changes but may yield information about the underlying distortion mechanisms. The paradigm analyzed here involves simultaneous presentation of two pure tones: the masker (ωr) at fixed amplitude (α) and an interrupted maskee (ωe) at levels (β) adjusted to threshold by the listener, i.e., the input amplitude A = α sinωrt + β sin(ωet + ϑ). With ωr:ωe = 2:3, one observer heard a low−pitched subjective signal as separately audible when ωr = 1000 Hz at 80 dB SPL. This subjective difference signal could be maintained at its own threshold by compensating β as the phase angle (ϑ) of ωe was successively incremented through 360°. Variations in β contain two increases and/or decreases with a 21−dB range. With ωr = 500 Hz at 80 dB SPL, similar phase dependencies ranging to 11 dB are obtainable even among listeners who disregard the pitch of the cueing signal. Such variations are not evident at α < 60 dB SPL. They can also be made to disappear if the difference frequency is masked by inclusion of an appropriately centered narrow−band noise. These observations seem best explained by postulating four auditory processes: polynomial nonlinearity, vector summation of equal frequencies, phase independence of perceptual thresholds, and asymmetric loss of sensitivity. While the quantitative predictions derived from these assumptions fit both the ranges and patterns of phase effects obtained from select listeners quite well, other aspects of the results suggest that the basic explanatory approach may need still further elaborations.

Subject Classifications: 65.56, 65.58.
Comparison of critical ratios and critical bands in the monaural chinchilla
Authors: Seaton William H. , Trahiotis Constantine
Published: October 2005

The major purpose of this study was to compare measures of critical ratios and critical bands in monaural chinchillas. Critical ratios were obtained from two groups of chinchillas tested at 0.5, 1, 2, and 4 kHz in each of three levels of broad−band noise. Critical bands were obtained by assessing the values of masked threshold in various narrow−bands of noise centered on each test frequency. The measures of critical ratios and critical bands were found not to be parallel as a function of frequency, as is the case for human subjects. The present data were compared to those reported for the monkey and were found to be in essential agreement.

Subject Classification: 65.58, 65.75; 80.50.
Free flexural vibrations of an elliptical ring in its plane
Authors: Sato Kenzo
Published: October 2005

The paper studies free flexural vibrations in the plane of an elliptical ring of constant cross sections. The present vibrations are considered in the elliptical coordinate system and the vibration displacements are expressed in terms of the series of Mathieu functions. The nondimensional eigenfrequencies calculate numerically are tabulated for various aspect ratios. The experimental results are obtained and are found to be in good agreement with the theoretical results.

Subject Classification: 40.26.
Sound−absorptive materials to meet special requirements
Authors: Wirt L. S.
Published: October 2005

Bulk sound−absorbing materials are not suitable for many applications involving liquids, air flow, elevated temperature, vibration, and severe space limitations. In aircraft, all of these design constraints can occur together. The simplest alternative to the bulk absorber is the single−layer absorber, comprising a permeable facing sheet over a closed compartmented air space. Single−layer absorbers meet some of the above design requirements but their impedance versus frequency characteristic is inherently inferior to that of a good bulk absorber. A wide variety of improved absorption characteristics may be attained by utilizing more acoustical elements and parallel as well as series connections among the elements. The use of resistance paralleled by lumped inertance and resistance provides a facing sheet whose resistance increases with frequency while the positive reactance decreases. Dissimilar air cavities arranged compactly in parallel provide airspace reactance that remains near zero over a broad range of frequency. The cutoff characteristics of miniature acoustic horn arrays may be exploited to provide a duel−frequency range of absorption. The upper−frequency range resembles that of a single−layer absorber, whereas the low−frequency absorption occurs in a controllable region of considerable bandwidth. These novel sound−absorbing structures may provide practical solutions to such diverse problems as fan−jet engine buzzsaw noise, combustion noise, and noise due to cooling towers and car−wash installations.
Diffuse sound reflection by maximum−length sequences
Authors: Schroeder M. R.
Published: October 2005

Low−correlation sequences, such as ’’maximum−length’’ and Barker sequences and certain complex (magnitude one) sequences having flat power spectra, are ideally suited for designing surfaces of hard walls with highly diffuse reflections. Recent subjective−preference evaluations [M. R. Schroeder, D. Gottlob, and K. F. Siebrasse ’’Comparative Study of European Concert Halls’’, J. Acoust. Soc. Am. 56, XXX−XXX (1974)] indicate that low−loss, high−scatter surfaces may be required for better concert−hall acoustics. Surfaces shaped to give reflection coefficients according to such sequences show the expected high scatter in model experiments with microwaves.

Subject Classification: 55.20, 55.40.
Acoustical correlates of flute performance technique
Authors: Fletcher N. H.
Published: October 2005

Measurements of physical parameters of performance technique for a group of experienced flute players are reported. Blowing pressure is found to be consistent among the players and intermediate between previous measurements by Bouhuys [J. Acoust. Soc. Am. 37, 453−456 (1965)] and by Coltman [J. Acoust. Soc. Am. 40, 99−107 (1966); 44, 983−992 (1968)]. Jet−length measurements agree with those of Coltman. Blowing pressure and jet length come near to satisfying the expected relationship but with some discrepancy which may be significant. Harmonic analysis of flute tone shows that amplitude variations from piano to forte are largely confined to the upper partials, particularly for notes in the low octave. A study of vibrato shows that this normally consists of an amplitude modulation of the upper partials of the tone with little change in the fundamental. The vibrato frequency is consistently about 5 Hz and is associated with a 10% variation in blowing pressure at that frequency. Physiological vibrato mechanisms are discussed and the acoustical nature of the vibrato is shown to be determined by the nonlinear jet excitation mechanism and the stabilizing effect of the narrow fundamental pipe resonance.

Subject Clasification: 75.35.
Anomaly in pitch perception
Authors: Schelleng John C.
Published: October 2005

While listening to a violinist, the author noticed that as an accompaniment of hearing loss his perception of the higher pitches deviates from normal by a large musical interval. Pitch is perceived as of separate overlapping components, each with its own dependence of frequency. Over most of the range of the main component, pitch in semitones is proportional to logarithm of frequency as normally expected, but the range (for the left ear) ends at 1.4 kHz, fully exposing a second component about half an octave too high. This in turn ends at 1.8 kHz, exposing a third component higher still. In the lowest octave of the first component, pitch deviates continuously above normal and a fourth component appears below normal. The higher components are damaging to music and of unknown value for speech.

Subject Classification: 65.54.
Dichotic forward and backward ’’masking’’ between CV syllables
Authors: Repp Bruno H.
Published: October 2005

Dichotic CV syllables were presented at stimulus onset asynchronies (SOAs) between 0 and 480 msec in two ear−monitoring tasks (’’forward’’ and ’’backward masking’’). The design included indentical pairs and orthogonally varied stimulus intensities. A ’’similarity effect’’ (higher recognition scores when the target syllable contrasted on fewer features with the ’’masking’’ syllable) was found over the whole masking range (ca. 300 msec). Other findings included strong effects of both target and mask intensities, a ’’lag effect’’ but no right−ear advantage, and generally opposite effects on identical and nonidentical pairs. Identical pairs showed no masking at all. A model is suggested to account for the pattern of errors in dichotic listening: confusions are assumed to arise from nonspecific capacity limitations (’’perceptual noise’’), separately for each stimulus (hemisphere), and, at short SOAs, responses are assumed to be frequently assigned to the wrong channel. In addition, fusion may occur at very short SOAs. It is further argued that little direct interaction between dichotic inputs may take place; that central convergence occurs at a late stage in processing; that the assumption of a feature processing stage as distinct from a phoneme recognition stage may be unnecessary; and that the backward ’’masking’’ range cannot be equated with absolute processing time.

Subject Classification: 70.30.
Bulk modulus of a fluid−filled spherical shell
Authors: Hall Marshall
Published: October 2005

The zeroth mode of vibration of a fluid−filled elastic spherical shell is examined, and a simple expression is obtained for the bulk modulus of the shell. The expression obtained is a function of the bulk moduli of the fluid and the solid, the shear modulus of the solid, and the ratio of the external and internal radii of the shell. This formula approaches the correct asymptotic values when the internal radius approaches the external radius, and also when the internal radius approaches zero. If the shell is placed in an incompressible medium, it will have a resonance frequency which is determined by the bulk modulus of the shell and the density of the medium.

Subject Classification: 40.26.
Intensity discrimination for noise bursts in the presence of a continuous, bandstop background: effects of level, width of the bandstop, and duration
Authors: Moore Brian C. J. , Raab David H.
Published: October 2005

Weber functions for broad−band noise bursts were determined using a 2IFC procedure. Noise bursts were presented either alone or in the presence of a continuous, bandstop−filtered background whose spectrum level in the passband was 10 dB above that of the standard burst. The width of the bandstop was varied from 100 to 3160 Hz in half−log−unit steps. The center frequency of the bandstop was always 1800 Hz. Burst duration was either 10 or 250 msec, and levels ranged from 31 to 81 dB SPL. Weber fractions tended to increase with increasing level for all conditions using a bandstop background, but the effects were small. The form of the Weber function was similar for the long and the short duration bursts. Performance improved with increasing width of the bandstop, but the magnitude of the effect (on average, 2.5 dB per decade of bandwidth) was about half what would be predicted by stimulus−oriented models of discrimination (5 dB per decade).

Subject Classification: 65.35, 65.50.
Underwater localization of click and pulsed pure−tone signals by the California sea lion (Z
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Authors: Moore Patrick W. B.
Published: October 2005

The objective of this study was to measure the ability of the sea lion (Zalophus californianus) to localize click and pulsed pure−tone signals presented in the horizontal plane. In the first experiment the Minimum Audible Angle (MAA) was determined for a click signal consisting of one cycle of a 1.0−kHz signal presented with a repetition rate of 30 Hz. Thresholds at 63% and 75% correct responses were 6° and 9°, respectively. A second experiment examined the sea lion’s ability to localize pulsed pure tones ranging in frequency from 0.25 to 4.0 kHz at only one angular displacement. The pure tones were presented in the form of a pulse train, each pulse having a duration of 20 msec, rise−fall time of 5 msec, and a repetition rate of 30 Hz. The pulsed pure−tone localization function showed that as signal frequency was increased from 250 Hz to 1.0 kHz, the sea lion’s ability to localize the signal remained relatively constant, while above 1.0 kHz there was a sharp decrement in localization ability.

Subject Classification: 65.62; 80.60.
Extended modified ray theory field in bounded and unbounded inhomogeneous media
Authors: Davis James A.
Published: October 2005

Use of the generalized WKB procedure in place of the WKB procedure to obtain solutions to the separated wave equation leads to modified ray theory. The quantitative consequences of this frequency−dependent theory are investigated and compared with ordinary ray theory and normal−mode theory for both bounded and unbounded media under conditions for the formation of a shadow region in ordinary ray theory. The behavior of the modified ray theory field, which always contains a caustic in the types of problems which are examined, depends on whether the ray theory shadow boundary is a limiting ray or a caustic. In the former case the modified ray theory field, suitably extended to take the caustic into account, approaches the normal−mode field far into the shadow region. In the latter case the modified ray theory field in the shadow region agrees with the ordinary ray theory field, also suitably extended.

Subject Classification: 30.20.
Propagation of normal mode in the parabolic approximation
Authors: McDaniel Suzanne T.
Published: October 2005

The parabolic approximation to the acoustic wave equation is examined within the framework of normal−mode theory. For the case where sOund speed and water de pth are independent of range, three types of errors are found to occur. Discrete modes are shown to propagate with the correct amplitude and mode shape but with errors in phase and group velocities. In addition to these errors, which are inherent in the method, two other sources of error are present. The effect of these other errors may be made negligible in one case by limiting the sound−speed gradients and range considered and, in the other case, by introducing a highly absorptive layer deep in the ocean bottom.

Subject Classification: 30.20,30.50;20.40,20.15.