bluuebunny/crossref_metadata_2025 huggingface dataset:
Is the left hemisphere specialized for speech, language and/or something else?
Authors: Papçun George , Krashen Stephen , Terbeek Dale , Remington Roger , Harshman Richard
Published: October 2005

Morse code signals were presented dichotically to Morse code operators and to subjects who did not know Morse code. Morse code operators showed right ear superiority, indicating left hemisphere dominance, for the perception of dichotically presented Morse code letters. Naive subjects (i.e., subjects who did not know Morse code) showed right ear superiority, indicating left hemisphere dominance, (n.b.: same as Morse code operators) when presented with a set of dot-dash patterns which was restricted to pairs including seven or fewer elements, counting dots and dashes each as elements. The list restricted to pairs with seven or fewer elements in all was presented to the naive subjects at two levels of intensity, but even though the overall accuracy changed, the direction and degree of asymmetry as measured by the left ear contribution to the total errors remained constant. When presented with a list that included longer stimuli, naive subjects showed left ear superiority, indicating right hemisphere dominance, the opposite of their result with the shorter stimuli. We hypothesize that pairs consisting of the Magical Number Seven or fewer elements are perceived with reference to the subparts of which they are composed, but that longer stimuli force naive subjects to adopt strategies involving the holistic qualifies of the stimuli. Therefore we speculate that the left hemisphere is specialized for processing the sequential parts of which a stimulus is composed. Analysis of the substitutions made by Morse code operators does not reveal a phonetic basis for the lateralization of the stimuli as perceived by them. Consideration of our findings in the light of other literature on lateralization suggests that language is lateralized to the left hemisphere because of its dependence on segmental subparts, and that this dependence characterizes language perception as distinct from most other human perception.
Categorical and noncategorical modes of speech perception along the voicing continuum
Authors: Pisoni David B. , Lazarus Joan House
Published: October 2005

Native speakers of English identified and then discriminated between stimuli which varied in voice onset time (VOT). One group of listeners identified a randomized sequence of stimuli; another group identified an ordered sequence of stimuli, in which stimuli from the VOT continuum were presented in a consecutive order. Half of the Ss in each group then received one of two discrimination formats: the ABX discrimination test in which X was identified with A or with B, or 4IAX test of paired similarity in which two pairs of stimuli—one pair always the same and one pair always different—were presented on each trial. Noncategorical perception of the voicing distinction, reflected by an improvement in discrimination within phonetic categories, was obtained for the group of listeners who experienced both the sequential identification procedure and the 4IAX discrimination test. The results are interpreted as providing evidence for separate auditory and phonetic levels of discrimination in speech perception.
An acoustic Doppler wind measuring system
Authors: Beran D. W. , Willmarth B. C. , Carsey F. C. , Hall F. F.
Published: October 2005

A system using the Doppler shift of audible sound waves to measure atmospheric winds to heights of 1 km above the surface is described. Planned application of the device at a commercial airport required extensive transducer and antenna shielding to reduce the effect of ambient noise. Comparisons of winds measured by both the acoustic Doppler system and standard radiosondes indicate that high accuracy and resolution can be achieved, and that the wind profiles can be continually monitored with relatively simple ground based equipment.
Relation between the critical bandwidth and the frequency-difference limen
Authors: Moore B. C. J.
Published: October 2005

It is generally assumed that the frequency-difference limen is a constant fraction of the critical band-width. This relationship is found not to hold for frequency-difference limens measured in a two-interval forced-choice task.
Farfield performance of parametric transmitters
Authors: Berktay H. O. , Leahy D. J.
Published: October 2005

Since Westervelt's original proposal [J. Acoust. Soc. Am. 35, 535–537(1963)] that nonlinear acoustic interactions may be used to produce relatively narrow beams of sound at relatively low frequencies, a great deal of effort has gone into the study of parametric transmitting arrays, both experimentally and theoretically. In this paper, the behavior of such arrays in their farfield is studied, neglecting higher-order interaction effects. Results are presented in the form of normalized curves and simplified equations which can be used for the preliminary design of such devices.
Eigenfrequencies of thin plates and layer potentials
Authors: Vivoli J. , Filippi P.
Published: October 2005

In this paper the authors represent a general solution of the homogeneous plate equation, valid on both the domain of the plate and its plane complement, in terms of potentials which are generated by source layers, located on the plate boundary, of two different orders. From the conditions that describe the physical properties of the plate boundary, system of integral equations for the layer densities is obtained. It may be shown, using layer potentials of order ⩽3, that this integral formulation of the problem is equivalent to the differential one: in particular, the integral system has the same eigenfrequencies as the differential one. Two examples are given which reveal that the numerically computed eigenfrequencies of the integral system are in good agreement with experimental results.
Tubular windscreen design for microphones for in-duct fan sound power measurements
Authors: Wang John S. , Crocker Malcolm J.
Published: October 2005

The design of tubular windscreens (sometimes called sampling tubes) for in-duct fan sound power measurements is described. Such sampling tubes might be used in the field, although the motive for the present study was the development of a windscreen (sampling tube) for use in an in-duct fan sound power measurement standard. The head-on frequency response, directivity, and turbulence rejection of several different designs of sampling tubes have been measured. A theory to predict head-on frequency response and directivity of the sampling tube has been developed. The basic governing equations were derived from the conservation of mass and conservation of momentum with the assumption that the particular thermodynamic process is an adiabatic one. The theoretical results are in good agreement with the experimental results.
Cochlear waves: interaction between theory and experiments
Authors: Zwislocki J. J.
Published: October 2005

Review of past experimental and theoretical research leads to a statement of the mechanism producing the vibration maximum in the cochlea. It is shown that theoretically calculated propagation times of cochlear waves agree with the empirical data. The waves have a frequency-independent propagation velocity between the stapes and the vicinity of the vibration maximum. This means that they must be considered as “long waves” in this part of the cochlea. On the basis of the theoretically derived and experimentally confirmed resistive input impedance of the cochlea, a sound pattern is devised for an analytical investigation of auditory nerve responses. Application of the pattern reveals that single units of the nerve respond to both velocity and displacement of the basilar membrane. Motion or displacement toward scala tympani produces excitation, motion, or displacement toward scala vestibuli, inhibition. These results indicate that both inner and outer hair cells excite the same nerve fibers.
Intracellular responses to acoustic clicks in the inner ear of the alligator lizard
Authors: Weiss Thomas F. , Mulroy Michael J. , Altmann David W.
Published: October 2005

Micropipets were used to record electric responses to acoustic clicks in single hair cells and supporting cells in the basilar papilla of the inner ear of the alligator lizard. Intracellular responses were less than 3-mV peak-to-peak and the relation between intracellular response and sound pressure at the tympanic membrane was nonlinear. Two types of intracellular responses to acoustic clicks were identified: type A has a dominant oscillatory component whose polarity is reversed when the polarity of the click is reversed. Type B has a dominant positive component that occurs at the time of the neural (N1) component. In a few cases, the technique of intracellular dye-marking was used to determine the cellular recording site of these waveforms. We tentatively conclude that type A responses are recorded in hair cells and type B in supporting cells. The initial polarity of the oscillatory component of the response appears to correlate with the morphological polarization of hair cells in the papilla. Fourier transforms of responses to acoustic clicks demonstrate that frequency-selectivity (tuning) occurs in the intracellular potential. A model of the papilla is proposed which is qualitatively consistent with response waveshapes and the morphology of the papilla.
Coding of sounds with rapidly varying spectrum in the cochlear nucleus
Authors: Møller Aage R.
Published: October 2005

The discharge pattern of a single unit in the cochlear nucleus in response to tones and noise bands of which the frequency was modulated trapezoidally over a large frequency range, including the response area of the unit, was studied. The distribution of nerve impulses was found to change in a characteristic way as a function of rate of change in frequency. The probability of firing within a narrow frequency range around the characteristic frequency (CF) of all units studied has a maximal value at a certain (high) rate of change in frequency. At that rate the peaks in the cycle histograms of the responses often became more than ten times higher than at low sweep rates. The effect was seen in the high-intensity range (more than 60 dB) but it was less pronounced near the threshold of the unit. The threshold did not become lowered at any rate of frequency change. A similar pattern was seen in response to bands of noise of which the frequency was varied in the same way as the tone. The magnitude of increase in height of the peaks in the histograms was usually somewhat less for noise than for tones.
Role of formant transitions in the voiced-voiceless distinction for stops
Authors: Stevens Kenneth N. , Klatt Dennis H.
Published: October 2005

Previous research on acoustic cues responsible for the voiced-voiceless distinction in prestressed English plosives has emphasized the importance of voicing onset time with respect to plosive release (VOT). Voiced plosives in English normally have a short VOT (less than 20–30 msec) and a significant formant transition is present following voice onset. Voiceless plosives in prestressed position, on the other hand, have relatively long VOT's (greater than about 50 msec) and the formant transitions are essentially completed prior to voice onset. Our experiments with synthetic speech compare the role of VOT and the presence or absence of a significant formant transition following voicing onset as cues for the voiced-voiceless distinction. The data indicate that there is a significant trading relationship between these two cues. The presence or absence of a rapid spectral change following voice onset produces up to 15-msec change in the location of the perceived phoneme boundary as measured in terms of absolute VOT. One can speculate that the auditory system may be predisposed to detect the presence or absence of a rapid spectrum change as a general property of acoustic inputs. If this is the case, then the acquisition of the voiced-voiceless distinction in infants may be conditioned initially by the presence or absence of this property at the onset of voicing rather than by absolute VOT.
Dichotic release from masking for speech
Authors: Rand Timothy C.
Published: October 2005

A dichotic method of listening to synthetic CV speech syllables was investigated, where the first formant (F1) is presented to one ear and the second and third formants (F2, F3) to the other ear. As a test parameter, the intensity of F2, F3 was varied. Compared to the binaural condition, dichotic presentation permits F2, F3 to remain effective as speech cues at significantly lower intensity levels. The results are given the following interpretation: peripheral masking, which occurs for ordinary binaural listening, is avoided when speech is heard dichotically. A similar release from masking was found in a second, related experiment where only the initial F2, F3 transitions were presented to one ear and the remainder of the syllable to the other.
Noise control versus shock and vibration engineering
Authors: Morrow Charles T.
Published: October 2005

Noise control and shock and vibration engineering have many fundamentals in common and many analogous practical constraints. Yet, in many respects they tend to be opposite in methodology, philosophy, and past history. The present discussion is an attempt to present the point of view of the practicing engineer, in either field, who has some perspective on the historical origins of his art. It focuses on aspects that epitomize the practical objectives of such engineers plus any administrators, lawyers, etc., who may also be involved in team efforts. For noise control, the aspects chosen are establishment of regulations, monitoring, and design or other actions intended to bring about compliance with regulations. For shock and vibration engineering, they are establishment of environmental specifications to ensure reliability, environmental testing in accordance with these, and design or redesign to bring about compliance with test requirements and also (we hope) to bring about reliability without severe penalties in weight, schedule, or cost. This is not to say that these aspects in their barest sense represent all the technology or methodology that is pertinent, or even that these limited aspects will be treated comprehensively. It is almost self-evident that the Acoustical Society of America should and does maintain beneficial relationship with medical, psychological, mechanical engineering, and other societies that report their particular developing lore of fundamentals and some practical information from their particular viewpoint. The Acoustical Society is an important part of this spectrum by virtue of its interdisciplinary coverage, extending through materials, dynamics, sound, instrumentation, and electronics to speech and hearing. But it is also worthwhile for the ASA, by whatever means are available, to sample the flavor of various disciplines as unified and value-weighted in accordance with typical practical objectives. For this reason, the developing beneficial relationships with the Institute of Noise Control (INCE) and the Shock and Vibration Information Center (SVIC) will become increasingly important.
Spatial variability of underwater ambient noise at the Arctic ice-water boundary
Authors: Diachok O. I. , Winokur R. S.
Published: October 2005

Quasisynoptic measurements were made to determine the spatial variability of ambient noise at the Arctic ice-water boundary over a frequency range from 100 to 1000 Hz. The results of this investigation show that the ice-water boundary acts as a spatially well-defined source of ambient noise with measured noise levels near a compact edge about 12 dB higher than open water levels and about 20 dB higher than levels far in the ice field. Measured noise levels near a diffuse ice edge were about 4 dB higher than open water levels, and about 10 dB higher than levels far in the ice field. The relatively high noise levels at the ice edge are probably generated by wave and swell interactions with individual ice floes.
Thresholds of audibility for very low-frequency pure tones
Authors: Yeowart Norman S. , Evans Margaret J.
Published: October 2005

This paper presents new binaural-hearing-threshold data obtained (a) by an earphone method over the frequency range 5–100 Hz and (b) by a whole body chamber method over the range 2–20 Hz. The results obtained are in excellent agreement with recent reported data. The binaural to monaural listening advantage appears to remain at 3 dB throughout the frequency range. A good approximation to the binaural threshold of hearing may be formed by lines from the point 92.0 dB SPL at 15.5 Hz with slopes of 12.3 dB/octave for frequencies below 15.5 Hz and 22.2 dB/octave above.
Talker differences as they appear in correlation matrices of continuous speech spectra
Authors: Li K.-P. , Hughes G. W.
Published: October 2005

The properties and measurement of intertalker and intratalker variability among correlation matrices derived from spectra of continuous speech are described. Measures of difference between two matrices are applied to quantify talker variability. These measures of difference are consistently less for intratalker data than for intertalker comparisons. For a population of 30 talkers, the distributions of these differences show about 1% overlap to confound absolute identification of a given talker. The effects of spectral shaping and sample size are discussed, and applications to talker identification and normalization schemes suggested.
Low false-alarm rates in signal detection by marine mammals
Authors: Schusterman Ronald J.
Published: October 2005

Psychophysicists attempting to obtain acoustic threshold estimates in marine mammals have been relatively unaware of setting up reinforcement contingencies which have resulted in their animals using a Neyman-Pearson objective as their response criterion. Low false-alarm rates strengthen the investigator's idea that he has acquired good stimulus control over the animal's behavior but may also lead to underestimates of sensitivity. Where possible, psychophysical procedures with animals should be amenable to analysis of response bias independent of sensitivity.
Forced vibrations of laminated composite plates in cylindrical bending
Authors: Sun Chang-Tsan , Whitney J. M.
Published: October 2005

In this paper the classical method of separation of variables combined with the Mindlin-Goodman procedure for treating time-dependent boundary conditions and/or dynamic external loadings is extended to investigate the dynamic response of laminated composite plates. The validity of this method applied to laminated composite plates under cylindrical bending is first established by showing that the principal modes of free vibration are orthogonal. The formal solution of the general forced vibration problem is then obtained. By means of the result, a specific example is worked out for a simply supported infinitely long laminated plate subjected to suddenly applied uniform dynamic pressure.
Pure-tone intensity discrimination: some experiments relating to the “near-miss” to Weber's law
Authors: Moore Brian C. J. , Raab David H.
Published: October 2005

Intensity DLs for pulsed tones (f = 1000 Hz) were determined at two sensation levels. As has previously been noted, discrimination was better at the higher level. The possibility that this effect reflects the subject's use of information from aural harmonics was tested using stimuli specifically designed to disrupt such information. These stimuli did affect discrimination, but only when they were at levels in excess of those which would be required by the usual estimates of aural harmonic magnitudes. Further experiments with interfering stimuli used three types of noise: wide-band, high-pass, and band-stop. The noises had equal energies in the critical band around 1000 Hz and had spectrum levels in their respective pass-bands of −60, −30, and −35 dB relative to the 1000-Hz test tone. The noises had no effect on performance at the lower sensation level. At the higher level, performance was impaired, the greatest impairment being produced by the band-stop noise, the least by the wide-band noise. This was interpreted as indicating that information on both the high- and low-frequency sides of the test tone affects intensity discrimination at high levels. Implications of these results for models of intensity discrimination are discussed.
Model for mechanical to neural transduction in the auditory receptor
Authors: Schroeder M. R. , Hall J. L.
Published: October 2005

We describe a model for transduction of displacement of the basilar membrane to activity of auditory nerve fibers. The model is physiologically oriented. Quanta (“vesicles”) are added to a population inside an urn (hair cell) at a fixed average rate. They are removed from the population with a probability proportional to the number of quanta in the population and related in a simple manner to the instantaneous amplitude of the input signal (displacement). The removal of a quantum results in an event (action potential) with a probability related to time elapsed since the preceding event (refractory period). Apart from refractoriness, the model is completely specified by three parameters which determine spontaneous and maximum firing rates and the time constant of recovery after intense stimulation. The model is more compatible with observed activity of the auditory nerve than threshold-crossing models. An important feature of auditory-nerve data reproduced by the model is the level normalization observed at moderate to high stimulus intensities. The model reproduces features of period, PST, and interval histograms in response to pure and complex tones, tone bursts, and noise. We present results both from analysis and from computer simulation of the model.
Model for wave propagation in a lossy vocal tract
Authors: Sondhi M. M.
Published: October 2005

Wave propagation in a lossy vocal tract with yielding walls is described in terms of an idealized, three-parameter model. It is shown how the parameters of the model may be determined from terminal acoustical measurements on the vocal tract. Evidence is presented for the adequacy of the model. Some applications are suggested.
Directional correlation functions of the sea surface
Authors: Mellen R. H.
Published: October 2005

The Roll-Fisher wave-height frequency spectrum of the fully developed sea yields closed-form spatial correlation functions for arbitrary wave directionality and asymmetry when separability of the wavenumber spectrum and the directionality function are assumed.
Bilateral hearing asymmetry in a large population
Authors: Kannan Phillip M. , Lipscomb David M.
Published: October 2005

A statistical study was undertaken to determine if there are statistically observable differences in left-right levels of studies reported by the Public Health Service. The results of nonparametric analysis indicate that the two ears are not significantly different in females. Males, both young and mature, demonstrated that the right ear is significantly more often the more sensitive ear to audiometric test tones.
Influence of gravity on wave propagation in an elastic layer
Authors: De S. N. , Sen-Gupta P. R.
Published: October 2005

In the present paper the influence of gravity on the propagation of waves in an elastic layer is studied. The classical equations of motion for the propagation of elastic waves in a homogeneous isotropic elastic solid medium are modified by Biot's theory of initial stress on the assumption that the force of gravity creates a type of initial stress hydrostatic in nature. It is shown that the gravity field has some effect on the wave velocity when the length of the wave is small compared with the thickness of the layer, while in the contrary case the effect of gravity is insignificant.
Condenser-microphone arrays in acoustical holography—a review
Authors: Nigam Anant K.
Published: October 2005

The primary difficulties in producing acoustical holograms have been associated with the recording technique. This paper presents some of the important recording techniques and highlights the desirability and advantages of using two-dimensional arrays of linear, electroacoustic transducers for detecting holographic data in real time. Recent developments of a class of such arrays, namely the condenser-microphone arrays, are reviewed. This is followed by an outline of the major considerations involved in the design of such arrays, the discussion of their characteristics, and their immediate and future prospects in acoustical holography.
Transverse vibrations of double-tapered cantilever beams with end support and with end mass
Authors: Mabie H. H. , Rogers C. B.
Published: October 2005

The free vibrations of a double-tapered cantilever beam with (1) end support and (2) end mass have been investigated using the Bernoulli-Euler equation. The beam was tapered linearly in the horizontal and in the vertical planes simultaneously with the taper ratio in the horizontal plane equal to that in the vertical plane. A table is presented for the first case from which the fundamental frequency, second, third, fourth, and fifth harmonic can easily be obtained for various taper ratios. A chart, plotted from this table, shows the effect of taper ratio on the various harmonics. For the second case, a table and resulting charts show the effect of taper ratio and ratio of end mass to beam mass on the fundamental frequency and higher harmonies. Although previously presented, the case of the beam with free end is also included for purposes of comparison.
Acoustic reflection from elastic spheres. I. Steady-state signals
Authors: Neubauer Werner G. , Vogt Richard H. , Dragonette Louis R.
Published: October 2005

Measurements are made of the acoustic reflected pressure from aluminum and tungsten-carbide spheres for ka values between 5 and 20. Only the farfield monostatic case is considered. Experimental values are compared to a harmonic-wave solution. Excellent agreement is observed when the wave speeds in the sphere material are adjusted by an amount smaller than the known uncertainty in the wave-speed values in the solids. The position of rapid changes in the reflection solution with ka is found to be very sensitive to shear-wave speed and insensitive to longitudinal-wave speed. The sensitivity to ambient temperature of the position of a selected minimum in the reflection solution is examined computationally for an aluminum sphere. A shift in the value of ka at which a minimum is calculated is also observed experimentally. Long pulses are used to approximate steady-state conditions and agreement with the steady-state theory shows that this approximation is adequate.
Multiple eigenvalues of sound-absorbing circular and annular ducts
Authors: Zorumski William E. , Mason Jean P.
Published: October 2005

Eigenvalue equations of the form D(λ)=0 are studied for acoustic modes in circular and annular ducts without flow. The ducts have locally reacting walls with arbitrary wall admittance. It is shown that circular duets may have double eigenvalues, or wall admittances where both D(λ) and D′(λ) are zero. These double eigenvalues are formed by the coalescence of the lowest-order eigenfunction with some higher-order eigenfunction. The eigenfunctions, or acoustic modes, associated with the double eigenvalues are found to be orthogonal to themselves so that the standard expansion formula for the acoustic field, which is obtained from a separation of variables analysis, is invalid. An alternate expansion formula for the acoustic field is derived. This alternate formula shows that the coalesced acoustic mode is linearly amplified by the transmission distance and exponentially attenuated at the expected rate. The expansion formula also reveals a new eigenfunction, or acoustic mode, which is exponentially attenuated the same rate as the coalesced eigenfunction. It is shown that annular ducts may have double eigenvalues for arbitrary values of one of the wall admittances. Annular ducts may also have triple eigenvalues, or selected values of the wall admittances, where D(λ), D′(λ), and D″(λ) are all zero. The associated triple eigenfunctions are shown to be self-orthogonal. The expansion formula for the sound field in an annular duct with a triple eigenvalue shows a quadratically amplified acoustic mode, a new linearly amplified mode, and another new mode, all of which are exponentially attenuated at the same rate. Methods of calculating single eigenvalues by means of numerically integrating ordinary differential eigenvalue equations are given and discussed with regard to multiple eigenvalues. Results are presented showing double eigenvalues of circular and annular ducts and triple eigenvalues of annular ducts.
Discrete tones of isolated airfoils
Authors: Tam Christopher K. W.
Published: October 2005

Recent experimental measurements reveal that discrete tones are emitted by isolated airfoils under certain operating conditions. Arguments are presented that these tones are unrelated to vortex shedding processes as has been suggested. It is proposed that the tones are generated by a self-excited feedback loop of aerodynamic origin. The loop consists of large-scale unstable disturbances in the boundary layer and wake flow and the feedback acoustic waves. Quantitative deductions based on the feedback loop model compare favorably with experimental measurements. It is also found that the proposed model is consistent with the observed characteristic features associated with the discrete tone phenomenon.
Natural vibrations of systems of elastically connected Timoshenko beams
Authors: Rao S.S.
Published: October 2005

The differential equations governing the flexural vibrations of systems of elastically connected parallel bars are derived considering the effects of rotary inertia and shear deformation. These equations are solved to find the natural frequencies and mode shapes of particular three- and two-beam systems. For the two-beam system, the present results are compared with the available experimental values.
Intensity and frequency discrimination in one- and two-interval paradigms
Authors: Jesteadt Walt , Bilger Robert C.
Published: October 2005

Both intensity and frequency discrimination data were collected for the same four subjects using several psychophysical paradigms. No differences were observed that would indicate that frequency discrimination involves fundamentally different decision-making processes than intensity discrimination. In both cases, performance in a two-interval forced-choice task exceeded performance in a yes-no task by a factor greater than the generally predicted √. Consistent individual differences were observed in frequency discrimination but not in intensity discrimination.
Effectiveness of linear prediction characteristics of the speech wave for automatic speaker identification and verification
Authors: Atal B. S.
Published: October 2005

Several different parametric representations of speech derived from the linear prediction model are examined for their effectiveness for automatic recognition of speakers from their voices. Twelve predictor coefficients were determined approximately once every 50 msec from speech sampled at 10 kHz. The predictor coefficients and other speech parameters derived from them, such as the impulse response function, the autocorrelation function, the area function, and the cepstrum function were used as input to an automatic speaker-recognition system. The speech data consisted of 60 utterances, consisting of six repetitions of the same sentence spoken by 10 speakers. The identification decision was based on the distance of the test sample vector from the reference vector for different speakers in the population; the speaker corresponding to the reference vector with the smallest distance was judged to be the unknown speaker. In verification, the speaker was verified if the distance between the test sample vector and the reference vector for the claimed speaker was less than a fixed threshold. Among all the parameters investigated, the cepstrum was found to be the most effective, providing an identification accuracy of 70% for speech 50 msec in duration, which increased to more than 98% for a duration of 0.5 sec. Using the same speech data, the verification accuracy was found to be approximately 83% for a duration of 50 msec, increasing to 98% for a duration of 1 sec. In a separate study to determine the feasibility of text-independent speaker identification, an identification accuracy of 93% was achieved for speech 2 sec in duration even though the texts of the test and reference samples were different.
Lecture demonstrations in acoustics
Authors: Pinkston E. R. , Crum L. A.
Published: October 2005

Lecture demonstrations are being used less and less in modern courses in acoustics. It is suggested that acoustics courses can be enriched and vitalized by demonstrations and that they should be used more often. Descriptions of some useful demonstrations are given and references to background material are listed.
Rayleigh-type surface wave on a linear viscoelastic half-space
Authors: Borcherdt Roger D.
Published: October 2005

The analytic solution for a Rayleigh-type surface wave on a linear viscoelastic half-space is obtained. The general viscoelastic solution predicts several properties of the surface wave distinct from those predicted by elasticity. The velocity, absorption coefficient, and displacement field are described theoretically.
Acoustic saturation of spherical waves in water
Authors: Shooter J. A. , Muir T. G. , Blackstock D. T.
Published: October 2005

The acoustic transmitting capacity of a medium is limited by nonlinear propagation effects. As the source amplitude is increased to very high levels, acoustic saturation sets in, a state in which the amplitude at a field point approaches a limiting value, independent of the source amplitude. A theoretical and experimental study of saturation of spherical waves is presented in this paper. Predicted saturation amplitudes for the fundamental component in an originally sinusoidal wave are obtained by matching the well known weak-shock solution to a linear-theory solution at the old-age distance rmax. The saturation formulas are verified by experiments done in fresh water with a 3-in.-diam piston projector operating at 454 kHz at source levels up to 135 dB re 1 μbar at 1 yd. Amplitude response curves were measured on the acoustic axis at six distances ranging from 0.76 yd to 111 yd. At the longer ranges the curves become isotonic, thereby demonstrating saturation. High-amplitude beam patterns show the effect of finite-amplitude attenuation in that the major lobe is broadened and minor lobe suppression is reduced. Finally, the saturation formulas are used to develop curves of maximum SPL as a function of range, with frequency a parameter, for both fresh and sea water.
On mechanisms of cavitational damage to biological tissues
Authors: Senapati N. , Lele P. P. , Caulfield J. B.
Published: October 2005

Experimental investigations have shown presence of cavitation in biological tissues during ultrasonic irradiation at low-megahertz frequencies. Most of the energy of acoustic emissions from the cavitating zone was found to be contained in the subharmonic portion of its spectrum. A mathematical model has been developed to describe the stress field associated with this cavitation power. The exact mechanism(s) of interactions of this stress and the tissue is essentially unknown. Therefore five possible “damage laws” based on threshold and cumulative damage criteria have been tested. The histologically observed diameter of the ultrasonic focal lesion in the central nervous system of cats was taken as the quantitative measure of the extent of damage. The functional nature of the theoretical correlation between the diameter of the lesion, irradiation power, and the duration of irradiation was compared with the empirical observations. The cumulative damage criterion based on fatigue failure due to random-stress was found to be the most likely mechanism of damage due to cavitation. However, this predicted damage was found to be smaller than the empirical value indicating effects of noncavitational mechanisms of tissue destruction. The possibility of the superimposition of cavitational and noncavitational damage in the core of the lesion is being investigated in ultrastructural studies. [This work was supported in part by USPHS Grant No. NIH-5-P01-HL14322.]
Statistical problems connected with the one-dimensional nonlinear diffusion equation
Authors: Burgers J. M.
Published: October 2005

The problem investigated refers to asymptotic solutions of the nonlinear equation ut + uux = νuxx in cases where “shocks” appear. Statistical probabilities are based upon the use of a collection (“ensemble”) of oscillating curves u0(x) as initial data. The ensemble is subjected to the condition that there shall exist a correlation function R(x2−xl) = u0(xl)u0(x2), with a prescribed magnitude J of its integral. A geometric method, based upon the Hopf-Cole solution of the nonlinear equation, is applied to find the positions of the shocks. The quantities to be evaluated are ensemble mean values of powers of the shock heights. The statistical problem is inverted so that it refers to contacts between oscillating curves deduced from the initial data, and a parabola. Some indications are given concerning the methods used in the extensive calculations needed for obtaining the desired mean values as exact expressions in terms of the time t and the value of J [see Proc. Symposium on Statistical Models and Turbulence, San Diego (15–21 July 1971), pp. 41–60]. [Work supported by AFOSR.]
Effects of middle-ear pressure on the auditory periphery
Authors: McPherson D. L. , Miller J. M.
Published: October 2005

A series of 52 young adult guinea pigs were used to study the effects of middle-ear pressure on the electrophysiological response of the cochlea. A round window electrode was used to record the cochlear microphonic (CM) and N1 action potential. Pure tones from 80 to 30 000 Hz were used to elicit the CM response; 0.1-msec clicks presented at ten clicks per second were used for N1 response studies. Middle-ear pressures ranging from −300 to +300 mm H20 were examined. Both pressure and frequency were examined in a pseudorandom order. CM response sensitivity (1 μV isopotential contour) and dynamic range of the CM were measured. Greater changes in the cochlear potentials were noted for negative pressures than for positive pressures. Also, it was found that there was a greater falloff of sensitivity of the CM as a function of pressure for small pressure variations than for greater pressure changes. The effects of middle-ear pressure were frequency dependent. Changes in the dynamic range of the CM were found to be consistent with predicted middle-ear transmission changes. [This research was supported by the Office of Naval Research N00014-67-A-0103-0031.]
Wide-band audible noise reduction using active compensation by secondary sources
Authors: Keller W. S. , Dunn W. R.
Published: October 2005

An alternate method to passive sound insulation is to employ active electronic control. In this approach, described earlier by Olson and others, one employs a microphone, amplifier, and loudspeaker connected in a feedback fashion to reduce noise. A fundamental limitation of these approaches is that the noise reduction is confined to fairly narrow range of frequencies. Tartakovsky's general principles of active compensation of vibrating systems are extended to realizing stable, active compensation of airborne sound fields having both finite wave propagation delay and finite transducer size. Design of an operative system is given along with other practical examples.
Nonlinear analysis of pressure field upstream of transonic rotors and generation of combination tones
Authors: Hanafi A. , Abdelhamid A. N.
Published: October 2005

Pressure field upstream of a transonic rotor with attached shock waves is determined using the rotational method of characteristic. In addition to the theoretical case of rotors with identical blades, the analysis includus the practical case of rotors with blade-to-blade variations due to manufacturing tolerances. The variations are produced in the analysis by assuming perturbations in the blade stagger angle and radius of curvature at the leading edge. Perturbation at one blade is shown to significantly modify the pressure field only at the following two blade channels. Investigations of static pressure waves upstream of the rotor with errors in neighboring blades indicate that the effects of manufacturing errors in the blades are linearly additive. Influence functions for errors in blade stagger angle have been deduced and the pressure pattern due to variety of error configurations has been obtained. Rotation of these pressure patterns results in noise spectra at blade passage frequency and multiples of the shaft rotation frequency, with the manufacturing errors inducing frequency and amplitude modulation effects. The relative intensity of the various harmonics is shown to be dependent on error configurations and the axial location upstream of the rotor. Correlated and uncorrelated error distributions are considered. Comparison with available experimental data, however, indicates that blade errors in actual rotors are essentially uncorrelated.
Two classes of abnormal responses recorded from auditory-nerve fibers of kanamycin-treated gerbils
Authors: Sokolich W. G. , Zwislocki J. J.
Published: October 2005

According to their abnormal responses to low-frequency triangular and click stimuli, auditory-nerve units of kanamycin-treated Mongolian gerbils could be divided in two classes. Units of one class exhibited an excitatory response during displacement of the basilar membrane toward scala vestibuli and had normal rarefaction-click latencies. Units of the other class exhibited an excitatory response during displacement of the basiliar membrane toward scala tympani and an inverted response to rarefaction clicks. Most units of the first class had high characteristic frequencies (CF), those of the second, low ones. Correlation of the CF distributions with known anatomical trends suggests that the units of the first class were controlled predominantly by the inner, those of the second, by the outer hair cells. Since it is reasonable to assume that we recorded from radial fibers, this would mean that in the normal state the outer and inner hair cells interact. Single-unit recordings obtained with the help of sinusoidal stimuli from both kanamycin-treated and untreated gerbils are consistent with these conclusions.
Updating of speech transmission parameters obtained from nonuniform analysis segments in a linear predictive speech compression system
Authors: Chandra Satish , Lin Wen C.
Published: October 2005

A linear predictive speech compression system based on stationary autocorrelation formulation is described. This system employs pitch synchronous analysis of 4-kHz bandlimited input speech sampled at 10-kHz rate. An all-pole speech production model has been assumed and a 10th-order linear predicter is used. Quantization properties of k parameters [Markel and Gray, “On Autocorrelation Equations as Applied to Speech Analysis,” IEEE Trans. Audio Electroacoust. (April 1973)], pitch and energy from a large speech data base, and phonetically balanced (PB) words and sentences are discussed. This paper emphasizes the updating of speech transmission parameters based on relative changes in normalized energy between two consecutive analysis intervals. The transmission rate is assumed to be constant but the frame size, for which the transmission parameters are used, is time variant. Thresholds have been defined for relative changes in normalized energy and changes in analysis interval size between two consecutive analysis intervals. Before compression, parameters are extracted every pitch period for voiced speech and every 8.5 msec for unvoiced speech. However, the parameters are used for transmission purpose if and only if the above-mentioned thresholds are exceeded. The parameters are forcefully updated when frame size becomes equal to maximum frame size, a preset value, even though the threshold criteria are satisfied. The transmitted parameters are pitch synchronously interpolated at the receiver end. Results of synthesized PB sentences at different bit rates are reported.
Neuronal response patterns in the cochlear nuclei: effects of vowel position on discharge rate
Authors: Rupert A. L. , Caspary D. M. , Moushegian G.
Published: October 2005

Single neuronal responses of the kangaroo rat cochlear nuclei to vowel sounds were studied. The vowel sounds used were [aye], [eye], [smcapi], [ɛ], [o], [u] [ɔ], [ə], [æ]. and [ṛ]. Each was approximately 40 msec in duration. Five were linked together to form a 200-msec stimulus. Eighteen combinations of the ten vowels made up the repertoire of stimuli. The results show that the neutral discharge rate to a vowel sound is appreciably changed as a function of where in the stimulus that vowel sound occurs. This vowel positional effect on the discharge is not the same for all neurons. Furthermore, the discharge rate to a particular vowel was greatly affected by the vowels which preceded it. The cytoarchitectonics and responses of cochlear nuclei neurons are related in an attempt to extract neural coding characteristics of this auditory aggregate. [Supported by Air Force Office of Scientific Research.]
Effect of longitudinal resonance the parametric stability of an axially excited cylindrical shell
Authors: Koval L. R.
Published: October 2005

The parametric stability of a cylindrical shell under pulsating axial load is studied wherein the internal axial stress resultant is computed on a dynamic basis with the shell acting as a longitudinal rod. A normal-mode expansion yields a system of ordinary differential equations with periodic coefficients, the stability of which is then examined. The effect of longitudinal inertia is found to increase the width of the “Mathieu-instability” regions, especially for those modes near the frequencies of longitudinal resonance. Combination resonances between the various transverse and axial-circumferential vibration modes of the shell are also found. These new features result from the inclusion of longitudinal vibration effects in the computation of the internal axial stress and are not present when N(x, t) is computed on a quasistatic basis.
Interaction of continuous and impulse noise: audiometric and histological effects
Authors: Hamernik Roger P. , Henderson Donald , Crossley James J. , Salvi Richard J.
Published: October 2005

Continuous and impulse noises were combined to model more realistic noise environments. Monaural chinchillas were exposed to one of the following conditions: (a) 50 impulses with 40-μsec. A duration at 158-dB-SPL peak pressure, 1/min; (b) 95-dB-SPL continuous noise at 2–4 kHz for one hour; (c) superimposed combination of the continuous and impulse noise; (d) 50 impulses with a 40-μsec. A duration at 175-dB-SPL peak pressure, 1/min; (e) interrupted combination of the continuous and impulse noise with the continuous noise off for 2 sec during the impulse delivery. Quiet thresholds were measured before and after exposure using the auditory evoked response and histology was obtained using the surface preparation technique. The audiometric and histological findings agree in showing that the superimposed combination of two noise exposures, shown to be safe for the chinchilla, produces traumatic effects that more than exceed the additive effects of either component. The existing damage risk criteria do not provide guidelines for such noise combinations.