bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling the perception of familiar words: Lexical access directly from spectra
Authors: Klatt Dennis H.
Published: October 2005

It is possible to formulate a strategy for continuous speech recognition that identifies familiar words directly from an acoustic (spectral) representation of the input, while making no intermediate decisions concerning phonetic features, phonetic segments, or syllables that might be present. One such algorithm utilizes a network to represent the phonetic transitions within each word by distinct sequences of spectra. Effects of cross-word-boundary phonetic recoding are incorporated in the network representation so as to be able to recognize all possible word sequences of the language. In principle, this “Lafs” (Lexical access from spectra) [D. H. Klatt, J. Phonetics 7, 279–312 (1979)] model can recognize words from fluent speech with greater accuracy than any two-stage model incorporating an intermediate phonetic level of representation. The reasons are (1) early phonetic decisions discard information important for lexical decisions, and (2) consideration of all possible phonetic strings will lead to more errors than consideration of only those phonetic sequences that make up legitimate word sequences. Such a model is worthy of consideration as a perceptual theory in light of its computational advantages, and in the absence of any disconfirming psychological evidence. However, it would be necessary to employ other (presumably phonetically based) strategies for the perception of unfamiliar words, so psychological validation/disconfirmation of a multiple-strategies perceptual hypothesis like this one will be difficult. [Work supported in part by an NIH grant.]
Do we need phonemes in speech perception?
Authors: Cole Ronald A.
Published: October 2005

Does speech perception involve the identification of a sequence of phonemes? Most theories of speech perception assume that speech is transformed into a sequence of phonemes at some point during the recognition process. Some theories (e.g., analysis by synthesis and the motor theory) hold that listeners transform speech into a phonemic code before recognizing words, while other theories hold that phonemes are generated as a result of recognizing words. I will argue that (a) there is no experimental evidence to support the claim that phonemes are involved in speech perception, since all experiments that purport to show such involvement are subject to alternative explanations, (b) when subjects are required to deal with speech as a sequence of segments, they use an orthographic (spelling) code rather than a phonemic code, and (c) on theoretical grounds, we should graciously accept the demise of the phoneme.
Models of speech perception: Lessons from recognition research
Authors: Reddy Raj
Published: October 2005

Over the past two decades, a number of speech recognition systems with varying degrees of generality, flexibility, and performance have been demonstrated. In this presentation we will examine different techniques of speech processing such as signal representation, adaptation to noise, speaker normalization, and segmentation and labeling and their possible relevance to perception studies. We will also examine the issues of acquisition, representation, and use of higher level knowledge such as lexical and syntactic knowledge.
More on “rays as interfering modes.”
Authors: Kamel A. , Felsen L. B.
Published: October 2005

The ray-like behavior of a cluster of normal modes furnishes a useful concept for determining the interference properties of a normal-mode pressure field. As formulated originally [C. T. Tindle and L. M. Guthrie, J. Sound Vib. 4, 291–295 (1974)], a selected group of modes is heuristically smeared out into a continuum, and it is established that the interference maximum lies along a path transversed by the “modal ray” for the central mode in the group. This approximate analysis does not quantify the corresponding amplitude behavior of the mode cluster. A rigorous basis may be provided by Poisson summation of the group of modes, which procedure incorporates systematically not only the transition to the continuum but also the effect of truncation of the mode bundle. As a result, a mode cluster may be shown to be completely equivalent, in phase and amplitude, to a ray field plus a remainder. The remainder can be minimized by an appropriate choice of the number of modes in the bundle and by weighting the first and last included modes. Examples are given for ray-mode fields in various ducting environments.
Perspectives on additive internal noise
Authors: Siegel Ronald A.
Published: October 2005

In a previous talk [R. A. Siegel and H. S. Colburn, J. Acoust. Soc. Am. Suppl I 63, S66 (1979)] we presented results of experiments in which additive internal/external noise variability ratios (σI/σE) were derived by measuring improvement of 2 IFC detectability of tonal signals in Gaussian maskers when the maskers in the two intervals were identical. σI/σE was measured for both NOSO and NOSII. Our estimate of σI/σE differed from estimates obtained by different procedures [e.g., D. M. Green, Psychol. Rev. 71, 1392–1407]. We present here a possible explanation for the discrepancy: By listening to different subintervals of identical maskers. subjects create independent effective maskers, thus precluding any improvement in threshold over that measured when truly independent maskers are presented in the two intervals. Our procedure thus appears inferior to procedures used by others. We warn other investigators about this pitfall which may be encountered in internal noise studies. We will also discuss implications on modeling of binaural interaction of our result that external noise is a significant factor in NOSII detection. We will concentrate on the widely held belief that binaural interaction serves to cancel out external noise, leaving only internal noise. [Work supported by NIH.]
The basics of mobility and impedance
Authors: Skudrzyk Eugen J.
Published: October 2005

Impedances and admittances of lumped parameter systems are described by “positive” functions which have specific properties. Foster's, Cauer's, and other theorems describe their driving-point behavior and their transmission properties. Mode methods generalize the theory for vibrators with continuously distributed parameters. The mobility turns out to be proportional to the mode contributions, whereas the impedance is found to be a mathematical artifice. The “point mode parameters” make it possible to introduce modal impedances even if force and displacement are spatial variables. Shell vibrators are of special interest; their modes consist of several coupled components with different resonance frequencies. If the resonances of a vibrator are well separated, maxima and minima of their response are determined by the contributions of the two modes whose resonance frequency is nearest to the frequency of the force. The mean line through the driving-point response is represented by the characteristic or mean value admittance, which is the analog of the characteristic admittance of a wave guide. Examples will illustrate the theory. [This work was sponsored by the Office of Naval Research, Code 474.]
Measurements and applications of mobility
Authors: Keller A. C.
Published: October 2005

The concept of frequency-response function measurements has been developed for many years. Originally conceived for use in feedback control systems design and circuit analysis, it is only in the past few decades that it has been applied to problems in structural dynamics. This paper traces the early development of instrumentation for making transfer function measurements, for many years called mechanical impedance plots. The rationale behind many of the analog techniques employed and their relationship to current digital methods is presented. The current state of commercial instrumentation is discussed, some of the uses to which measured functions are put is examined and some conclusions drawn.
Ultrasonic detection of resonant bubbles by their second-harmonic emissions
Authors: Miller Douglas L.
Published: October 2005

During bioeffects experimentation, determining whether cavitation will occur in a biological medium, or has occurred during an ultrasonic exposure is often difficult. This problem is particularly acute for low-intensity exposures when indicators, such as subharmonic emissions, are absent, or in situations in which ultrasonic scattering at the fundamental frequency is dominated by large bubbles, or other spurious sources, rather than by biologically effective resonant bubbles. A resonant-bubble detector has been developed which is based on selectively monitoring the second-harmonic emissions, in response to a low-intensity beam of ultrasound, from a liquid flowing in a tube or blood vessel which passes through the detector. Such emissions are expected only from resonant bubbles which scatter ultrasound nonlinearly. In tests, a detector using a 1.64-MHz beam and receiving at 3.28 MHz easily detected resonant bubbles which were about 4.5 p.m in diameter, but not 450-μm-diam bubbles. For in vivo use, this detector can be used as a perivascular cuff to detect either (i) pre-existing bubbles which may be present naturally and lead to cavitation during exposure, or (ii) resonant cavitation bubbles which have been generated upstream of the detector by ultrasonic exposure. [Work supported by USFDA Contract No. 223-79-6015.]
Reduced (3H) thymidine incorporation into human lymphocytes exposed in vitro to ultrasound may be due to DNA damage
Authors: Repacholi Michael H.
Published: October 2005

Alterations to the incorporation or uptake of (H) thymidine into mammalian cells exposed in vitro to ultrasound have been reported on a number of occasions [Prasad et al., Lancet, 1181 (29 May 1976); Fung et al., in Ultrasound in Medicine, edited by D. White and E. A. Lyons (Plenum, New York, 1978) Vol. 4, pp. 583–586; Repacholi et al., in Molecular Basis of Immune Function, edited by J. G. Kaplan (Elsevier/NH Press, Amsterdam, 1979) p. 443; Kaufman and Kremkau, in Ultrasound in Medicine, edited by D, White and E. A. Lyons (Plenum, New York 1978), Vol. 4, pp. 589–590. Evidence has now been produced [Repacholi, Ph.D. thesis, University of Ottawa (1980)] which suggests that the DNA of cells exposed to ultrasound at intensities above 2 W/cm2 may be damaged, possibly in the form of breaks, which need to be repaired before normal replicative DNA synthesis can proceed. Exposure of two day activated human lymphocytes in vitro to 4 W/cm2 ultrasound (870 kHz, cw, 30 min) causes an immediate, significant (P = 0.001) inhibition in the incorporation of (3H) thymidine. Auto-radiographic evidence [Repacholi and Kaplan, in Proc. of AIUM Convention, New Orleans, 42, ( 15–18 Sept. 1980)] suggests that the DNA is damaged and subsequently repaired. Preliminary experimental results using a fluorescing dye which intercalates double stranded DNA [Birnboin and Jecak, Cancer Res. (1981) in press] indicate that although ultrasound appears to produce damage to the DNA, part of this damage is rapidly repaired. The period of time required to completely repair the damaged DNA could account for the gradual increase in the (3H) thymidine incorporation to control levels observed in cells over the subsequent 2–3 days after sonication.
Low-frequency ambient noise in the deep Arctic ocean
Authors: Dyer Ira
Published: October 2005

Mechanisms and measurements of ambient noise in the deep Arctic Ocean will be reviewed and discussed. While emphasis will be placed on low frequencies (5 to 50 Hz), the review will consider the relationship to noise at higher frequencies. Also the contrast between shore fast/shallow water noise and deep water noise will be drawn. [Supported by ONR.]
Envelope statistics from cw signals propagated under the ice in the Arctic
Authors: Mikhalevsky Peter N.
Published: October 2005

Envelope statistic and tonal spectra have been measured from cw signals at 20 Hz, and 30 Hz propagated via an ice covered path over a range of 330 km. These data were taken during the TRISTEN II/FRAM II experiment mounted on the Polar Ice Cap over the Polar Abyssal Plain in April/May 1980. Measurements of tonal smear, fading rates, and comparisons with statistics as predicted by a phase random multipath fluctuations model are presented. [Work supported by Office of Naval Research.]
Paper noise in an impact printer
Authors: Busch-Vishniac Ilene , Lyon Richard
Published: October 2005

In many paper handling machines, the sound generated by impacts is a major noise source. It is shown that in typical impact line printers both nonresonant and resonant sound generating mechanisms are significant. Both can probably be controlled by increasing the backing bar stiffness of the printer while keeping the printing force constant. It is also shown that the paper-hammer-backing bar impact is responsible for paper impact noise below 1250 Hz. Above 2500 Hz the hammer-paper impact is the dominant source. From 1250–2500 Hz the two impacts contribute equally to the sound generation. Finally, consideration of the design of a “quiet” paper leads to the suggestion of a paper with high density and low bending rigidity. This might be accomplished through microcreping of the paper.
FRAM II basin backscattering data
Authors: Dyer Ira , Baggeroer Arthur B. , Williams Richard J.
Published: October 2005

As a sequel to experiments in the Beaufort Sea in 1978, basin-wide backscattering (reverberation) measurements were part of the 1980 FRAM II program. From an ice station in the East Arctic Ocean, TNT shots of mass up to 800 kg were used as impulsive sound sources, and the backscattered signals were observed with a horizontal 800 × 800 m array. Good signal-to-noise ratios were obtained for signals as far away as the Chukchi Sea, yielding high resolution estimates of the scattering function. Data at 10 Hz reveal many scattering loci, including submerged topographic features and the continental margins. Backscattering diagrams obtained in FRAM II are compared with those from the Beaufort Sea experiment, and conclusions are drawn on the experimental method as well as on the physical results. [Work supported by ONR.]
Multipole analysis of the directionality of ambient noise in the Arctic
Authors: Gaunaurd G. C.
Published: October 2005

We present an analysis of the directionality properties of ambient noise in Arctic regions based on the premise that ambient noise in the sea originates at its surface. Placing conceptual and suitable distributions of acoustic multipole sources at the sea surface, each one emitting sound with its own typical radiation pattern, it was possible to obtain predictions for the directional characteristics of arctic ambient noise, whatever its cause may be. An available theoretical model [R. J. Talham, J. Acoust. Soc. Am. 36, 1541–1544 (1964)] and ray-tracing programs were extended and modified to calculate the sound-intensity levels reaching a receiver per unit solid angle in the vertical plane for any receiver location. The results are valid for receivers looking toward the sea surface or the bottom, and the effects of a lossy ice surface and a lossy bottom were incorporated into the analysis. The angular distribution of intensity at the receiver is displayed in a variety of graphs for six (deep and shallow) geographical locations within the Attic region, various receiver depths, and several types of surface radiators and/or environmental parameters. Under several simplifying conditions satisfied only in rare instances, these elaborate calculations agree well with a straight forward analytical prediction discussed by Urick; otherwise, the elaborate calculations are a must.
LNG carrier underwater noise in Baffin Bay
Authors: Leggat L. J. , Merklinger H. M. , Kennedy J. L.
Published: October 2005

Large powerful liquid natural gas carriers may soon ply Arctic waters year round. Concern has been expressed over the impact the resulting noise will have on Arctic marine life. This study includes estimates of LNG carrier-radiated noise source levels and resulting sound levels at a given distance from the ship for a number of operating conditions. Measurements of sound propagation and ambient noise conditions in Baffin Bay are used to estimate the ship noise levels in relation to the summertime noise background.
Acoustic reflex in normal and learning disabled children
Authors: Johnson David W.
Published: October 2005

Seven “normal” (Group I) and thirteen “learning disabled” (Group II) children were evaluated for acoustic reflex thresholds ipsilaterally and contralaterally using pure tone stimuli at 0.5, 1, and 2 kHz and broadband white noise stimuli at maximum T.M. compliance. Mean acoustic reflex thresholds did not differ significantly for the two groups either ipsilaterally or contralaterally by t-test. Normals (I) showed no significant difference between ears for ipsilateral and contralateral acoustic reflex thresholds for any stimulus mode. L.D. (II) showed a significant difference between ipsilateral and contralateral thresholds in the right ear at 0.5, 1, and 2 kHz (P values of 0.001, 0.01, and 0.10, respectively) and in the left ear at 0.5 and 1 kHz (P values of 0.01 and 0.10). Significant acoustic reflex decay re 10 dB R.T.S.L. at 1 kHz was noted in either group. These preliminary data suggest that L.D. children may be identifiable by noting difference in sensitivity between ipsilateral and contralateral acoustic reflex threshold for certain stimulus frequencies. [General Mills Foundation support for central auditory studies is noted.]
Recovery of the acoustic reflex response as a function uf noise exposure and quiet interval durations
Authors: Lalande Nicole , Hétu Raymond
Published: October 2005

Recovery of the contralateral acoustic reflex response following various durations of monaural broadband noise exposure and quiet interval was investigated with six subjects. The level of the noise was 105 dB LpA. Four duration conditions for a continuous noise were selected: Two conditions involved the minimal exposure time that induced respectively 20% and 40% reflex adaptation; the other two conditions were 6- and 12-min exposures; these two durations were associated with a residual response corresponding to a reflex adaptation greater than 40%. Recovery of the reflex response was measured after pauses of 1, 5, 10, 30, and 50 s. It was hypothesized that the recovery of the reflex as a function of the duration of the pause, would be the same for noise exposures of 6 and 12 min, exposures which caused the same amount of adaptation, but would be greater for exposures giving rise to less reflex adaptation. Results confirmed the hypothesis for pauses of 1, 5, 10, and 30 s, but not for a pause of 50 s. Implications of these results will be discussed.
Finite-element modeling of the middle-ear ossicles
Authors: Funnell W. R. J. , Phelan K. E.
Published: October 2005

The finite-element method is a powerful technique for the analysis of complex mechanical structures. Its use in a model of the eardrum has been described previously [W. R. J. Funnell and C. A. Laszlo, J. Acoust. Soc. Am. 63, 1461–1467 (1978)]. This paper describes preliminary work on creating a finite-element model of the middle-ear ossicles of the cat. The shape of the model was derived from a series of histological sections, with the outlines of the ossicles being entered into the computer using a digitizer. The model was constructed using three dimensional ‘brick’ elements. The model will be presented, and its use in simulating ossicular mechanics will be discussed. [This work was supported by the Medical Research Council of Canada.]
A statistical analysis of third-octave speech amplitude distributions
Authors: De Gennaro Steven , Braida Louis D. , Durlach Nathaniel I.
Published: October 2005

Amplitude distributions which probabilistically describe the level variations present in third-octave bands during speech have been obtained through the periodic sampling of the short-term rms speech envelope in each band. Representative density functions are presented for a variety of speech materials including isolated CVC syllables and nonsense sentences spoken by male and female talkers. In general, the amplitude distributions do not have simple analytic forms, although they can be described parametrically in terms of cumulative percent levels. Typically, the range of amplitudes between the 10% and 90% cumulative levels in each frequency band exceeds 40 to 50 dB. Detailed characteristics of the density functions, however, change significantly across frequency. In the low-frequency bands, the distributions are bimodal, reflecting distinct amplitude ranges for voiced and unvoiced speech segments. The distributions become unimodal and more peaked in the higher frequency channels. Comparisons of these results with previous characterizations of speech amplitude distributions [i.e., H. K. Dunn and S. D. White, J. Acoust. Soc. Am. 11, 278 (1940] are also presented. [Work supported by NIH.]
On the interaction between fundamental frequency and articulatory setting
Authors: Habick Timothy
Published: October 2005

Despite the apparent implications of much current research [P. Ladefoged et al., J. Acoust. Soc. Am. 64, 1027–1035 (1978)], fundamental frequency plays an important role in determining the levels of a speaker's formant frequencies, since F0 affects the articulatory setting that a speaker habitually chooses for speech. On the basis of a spectrographic analysis of the speech of 40 subjects from one speech community, the size and location of the phonemic system in two-formant acoustic space will be shown to vary as a function of three major parameters: Fundamental frequency, social forces (both determining articulatory setting), and the invariable dimensions of the vocal tract. In addition, several competing theories of this aspect of speech perception will be rejected. Specifically, the assertion that listeners calculate the size of speakers' vocal tracts in order to decode their speech will be argued against.
Design considerations for optimizing the intelligibility of a DFT-based, pitch-excited, critical-band-spectrum speech analysis/resynthesis system
Authors: Seneff Stephanie , Klatt Dennis , Zue Victor
Published: October 2005

The primary objective of the research to be described was to determine whether a particular critical-band spectral representation retains information sufficient for high-performance speech recognition. The technique employed to answer this question was to design a speech analysis/resynthesis system (vocoder) in which the synthesizer only made use of a critical-band spectral representation. The intelligibility of speech processed through this system was determined as a function of a number of design parameters. The magnitude spectrum was computed for overlapping windowed segments of the speech waveform every 10 ms. The critical-band spectrum (38 spectral coefficients) was derived by forming the appropriate weighted sums of DFT magnitude coefficients. The analyzer also made a voicing decision and estimated fundamental frequency based on low-frequency DFT peaks. During resynthesis, the full DFT magnitude spectrum was regenerated by interpolation between the 38 available coefficients. An inverse DFT, in which the phase was set to zero, yielded a finite impulse response that could be convolved with the idealized excitation source to reconstruct a speech waveform. Not surprisingly, the synthetic speech sounded muffled due to the width of the critical-band spectral peaks. Several algorithms were then developed to sharpen these peaks prior to resynthesis. The best algorithm, to be described, was compared with a similar DFT-magnitude vocoder without critical-band smoothing and with a linear-prediction vocoder, using a modified rhyme test. The results have implications for both speech recognition and vocoder design. [Work supported in part by an NIH grant.]
Real-time LPC analysis using digital signal processor chips
Authors: Hanson R. J. , Olive J. P.
Published: October 2005

This paper describes a procedure for determining LPC area parameters in real time. The analysis involves the following steps: High-frequency pre-emphasis, windowing, computing the autocorrelation coefficients, and their conversion to area parameters directly from the autocorrelation coefficients without first computing the predictor coefficients. Computer simulations show that 20-bit precision is sufficient to avoid significant errors in the conversion of the autocorrelation coefficients to area parameters if frame-by-frame normalization is used. Our results show that good speech quality can be maintained in synthesis by using 16 area parameters updated at 10-ms intervals. The real-time requirement of this analysis procedure cannot be met by any single signal processor chip which is currently available. We have, therefore, used a multiprocessor configuration of signal processor chips to perform the analysis in real-time. The Bell Laboratories DSP chip—capable of performing a 16 by 20 bit multiply with 40 bit accumulation in 0.8 μs—was found to provide the necessary precision and speed.
Underwater acoustics in the Canadian Arctic Archipelago
Authors: Verrall Ronald
Published: October 2005

DREP has made underwater acoustic measurements in the straits of the Canadian Arctic Archipelago since the late 1950's. It has been a challenging problem to design equipment and experimental methods that will perform well in the harsh Arctic environment. This paper presents a summary of the techniques that have been used and the results that have been obtained. One of the important characteristics is the great variability of the acoustic parameters. Ambient noise levels change by as much as 60 dB from season to season, and transmission losses depend strongly on ice roughness as well as on frequency and water depth.
A quantitative study of ambiguity in lipreading
Authors: Di Benedetto Maria Domenica , Destombes Francis , Tubach Jean-Pierre
Published: October 2005

Deaf people find it difficult to “read speech” from lips since many sounds such as /p, b, m/ or /t, d, n/ look alike on the lips (“confusion groups”). By performing statistical computations on a large corpus of spoken French (95 000 phonemes), based upon the frequencies of phonemes, diphones, and triphones, it is possible to assert the relative importance of the various confusion groups. We use information theory (conditional entropy, redundancy) to evaluate the impact of confusions on the spoken message information contents. Identification rates of nonsense CV and VC syllables are also considered. A classification of confusion groups according to the message degradation they provoke is proposed and is compared to the current state of the art in automatic phoneme recognition. It appears that a research effort is needed to improve automatic recognition of “difficult” phonemes (occlusives and nasals mainly). These results could prove useful in our research to design an automatic device which would provide visual “cues” to help the deaf to disambiguate the confusion groups.
Speech perception by hearing-impaired listeners: Effects of speech maskers
Authors: Gordon-Salant Sandra , Wightman Frederic L.
Published: October 2005

The aim of this study was to examine the masking effects of brief segments of speech with both normally hearing and hearing-impaired listeners. The target stimuli were 11 CV's from each of two continua, (be-de-ge) and (pe-te-ke). Stimuli on a continum differed only in F2 starting frequency. Maskers were either one of the four end-point CV's or one of four brief noise bursts, spectrally matched to the onset spectra of the end-point CV's. In order to assess the effects of the maskers, judgments of interstimulus similarity were obtained (via a triadic comparison paradigm) from six normal and six hearing-impaired listeners. The results (in the form of INDSCAL solutions) suggest that the CV maskers were more disruptive than the noise maskers for both normal and hearing-impaired listeners. In addition, the masking effects were greater for the hearing-impaired listeners than for the normal listeners in all conditions. Our tentative conclusion is that for both normal and hearing-impaired listeners, masking by competing speech sounds is determined primarily by the phonetic content of the masker, and less by its spectral content. [Work supported by NIH Grant No. NS12045.]
Changes to speech identification performance with full- and partial-cue synthetic syllables by subjects with age-related hearing impairment
Authors: Hannley M. , Dobbins E.
Published: October 2005

In a previous presentation before the Society (Hannley, Fall meeting 1980) we noted that aging listeners appear to have impaired frequency resolution of the same magnitude as younger listeners with comparable sensorineural hearing disorder. Such impairment, however, did not account for severely reduced ability to identify place of articulation in two-formant CV syllables. In this study we investigated the possiblity that reduced performance might be accounted for by the limited external redundancy of partial-cue speech stimuli presented to impaired auditory systems having limited internal redundancy. Three experiments were conducted. In the first, two- and three-formant consonant-vowel syllables synthesized with and without release bursts were presented to elderly listeners for identification of place of articulation. In the second experiment the amplitude of the release burst was increased; and in the third experiment F2 and F3 transition duration was increased. The results of the three listening conditions will be related to absolute performance differences, degree of hearing impairment, and evidence of central auditory component in the listeners.
Cochlear frequency selectivity and phonetic identification in aging listeners
Authors: Dorman M. F. , Marton K.
Published: October 2005

Frequency selectivity in aging listeners with sensorineural hearing impairment was assessed by measuring the width of PTC's and masking patterns. Phonetic identification was assessed by the shape of identification functions for stimuli from five acoustic continua. Three continua were based on cue duration. In another continuum, the location of a steady-state F2 was varied relative to a fixed F1. In yet another continuum, the direction of change of F2 was varied. Preliminary results suggest that phonetic identification was poorest for stimuli cued by changes in F2 transitions. Steady-state formant discrimination was slightly poorer than normal when the F2 of the “different” stimulus was lower in frequency than the “standard” F2 steady state. Phonetic identification was most normal for stimuli cued by changes in stimulus duration. The relationship between these data and frequency selectivity will be discussed.
Diffraction of waves by surface breaking cracks
Authors: Wall D. J. N. , Varadan V. V. , Varadan V. K.
Published: October 2005

The diffraction of waves by a crack breaking the surface of a homogeneous half-space is considered. By the use of image theory this problem is reduced to consideration of a cavity in an infinite homogeneous space. The null field or T-matrix method is used to obtain a system of algebraic equations which are solved by a numerical scheme for the surface displacement. Derived quantities such as the stress concentration factors and the scattered field are then calculated. Numerical results are presented for various crack shapes.
Acoustic wave scattering by elastic cylindrical shells in water
Authors: Varadan V. K. , Pillai T. A. K. , Varadan V. V. , Radlinski R. P.
Published: October 2005

Frequency dependence of acoustic wave scattering by an infinite cylindrical shell of arbitrary cross section is analyzed using the T-matrix approach. Numerical results are obtained for plane wave incidence normal to the axis of the shell but arbitrary with respect to the noncircular cross section for a range of frequencies. Results obtained for shells of circular and elliptical cross sections are compared with experimental results.
Elastic wave scattering from complex shaped flaws
Authors: Varadan V. V. , Varadan V. K.
Published: October 2005

In the ultrasonic nondestructive evaluation of flaws in elastic solids, the flaw shaped encountered are quite complex. This must be taken into account in the theoretical modelling of flaws. Often one finds a single flaw with a crack emanating from it or two flaws that are close together or intersecting. Numerical results will be presented for several scattering geometries, frequency range and comparisons with experimental results will be made.
Coding of the directional information by inferior collicular neurons of echolocating bats, Eptesicus fuscus
Authors: Schlegel P. A. , Jen P. H.-S.
Published: October 2005

In sound localization, an animal mainly depends upon the binaural comparison of interaural time and intensity differences. To achieve an accurate coding of the directional information of a sound source, the animal's auditory system should theoretically contain binaural neurons whose responses only change as a function of interaural time and intensity differences but do not depend upon the absolute level of the sound stimulus. With 3M KCl micropipette electrodes, 230 collicular units were isolated between the depths of 44 and 2092 μm of the brain surface. In addition, to examine the basic electrophysiological properties of those units, studies on the directional coding of a sound source were made on 38 units in which 24 units yielded complete data. Among those 24 units, 16 units changed their number of impulses as a function of both the location and absolute intensity of a sound stimulus. Thus, when a sound stimulus was delivered at different intensities, it had to be placed at different azimuths in order to elicit the maximal responses from the same investigated unit. The directional coding properties of these units apparently depend upon stimulus intensity. However, the remaining 8 units showed directional coding properties that was independent of stimulus intensity. They always fired maximally to a sound stimulus that was placed within a well defined range of azimuths regardless of stimulus level. Such an independence of stimulus level in directional coding could even persist up to a range of 50 dB above the threshold of an investigated unit. Apparently these units are ideal for coding the directional information of a sound source. [Work supported by DFG (SFB 45) of FRG, NSF BNS 80-07348, USPH 1-KO4-NS 00433-01.]
Acoustic reflex reactivation: Frequency effects
Authors: Campagnolo E. M. , Gray L. , Ruth R. A.
Published: October 2005

Reactivation of the acoustic reflex (AR) was studied in 11 subjects using a modification of the adaptation/reactivation paradigm developed by P. G. Stelmachowicz and D. J. Lilly [J. Acoust. Soc. Am. 65, 1501–1508 [1979)]. Test frequencies spaced symmetrically about two adaptor frequencies (2000 and 2800 Hz) were utilized to evoke changes in AR magnitude after the response had adapted to 50% of its initial magnitude. Both stimulus delivery and response recording were controlled by computer. Mean data suggest that the degree of reflex reactivation increases as the difference between the adaptor and test frequencies increases. However, as with the data of Stelmachowicz and Lilly (1979), the present data exhibit substantial variability both within and among subjects. The length of time taken to achieve 50% adaptation does not appear to be an important factor in the magnitude of the reactivated AR for group data. In general, these findings support the existence of a frequency-resolving element in the AR mechanism.
Acoustic power of jets
Authors: Richarz Werner G. , Keith Stephen
Published: October 2005

Recently Morfey and Howell (AIAA Paper 79-0595) have shown that the acoustic power emitted by jets does not appear to be in agreement with Lighthill's U8 scaling law. In the present investigation it is argued that source convection is the principal mechanism leading to a departure from the U8 law (unheated jets only). This claim is tested by computation of “effective sound power spectra” from published data. The jet noise data are corrected for Doppler shift as well as “convective amplification.” The results suggest that the excess noise of clean jets is only apparent and can be accounted for by a “source-oriented” sound power balance. The method is also applied to heated jets. In this case a unique interpretation is not possible owing to the possibility of coherence between the various source mechanisms. [Research supported by Natural Science & Engineering Research Council, Canada and the University of Toronto.]
Controlling jet noise with a fluid shield
Authors: Mangiarotty Rudolph A.
Published: October 2005

A method is discussed for controlling the propagation of jet noise from aircraft or power generating plant gas turbines, or other conditions where a high speed stream of fluid is ejected into a quiescent fluid field. Introducing a slower moving heated fluid stream (shield) between an aerodynamic jet and an observer reduces the jet noise reaching the observer. Various kinds of fluid shield are described including flame jets and thermal fluid jets. The physical phenomena involved in fluid shielding are discussed, as well as the mechanisms involved in controlling the generation of sound of fluid jets. Typical experimental results are discussed and the implementation of the concept on an aircraft engine are examined. [Work supported by The Boeing Company, IR&D Program.]
Comparison of predicted engine core noise with proposd FAA helicopter noise certification requirements
Authors: von Glahn U. , Groesbeck D.
Published: October 2005

Calculated engine core noise levels, based on NASA-Lewis prediction procedures, for five representative helicopter engines are compared with measured total helicopter noise levels and proposed FAA helicopter noise certification requirements. Comparisons are made for approach, level flyover, and takeoff procedures. The measured noise levels are generally significantly greater than those calculated for the core noise levels, except for the Sokorsky S-61 helicopter using two General Electric T-58 engines. However, the calculated engine core noise levels are generally at or within 3 dB of the proposed FAA noise rules. Consequently, helicopter engine core noise can be a significant contributor to the overall helicopter noise signature and, in all cases, will provide a floor to a further decrease in future noise regulations.
On the propagation of long waves in acoustically treated, curved ducts
Authors: Rostafinski Wojciech A.
Published: October 2005

A two-dimensional, detailed study is presented on the behavior of long waves in lined, curved ducts. The analysis includes a comparison between the propagation in curved and straight ducts. A parametric study was conducted over a range of wall admittance and duct wall separation. The complex eigenvalues of the characteristic equation, which in the case of a curved duct are also the angular wavenumbers, have been obtained by successive approximations.
The effect of inlet/outlet locations on higher order modes in silencers
Authors: Eriksson L. J.
Published: October 2005

A series of measurements were made using an impedance tube with a broad band noise generator and anechoic termination as well as a small, four-stroke, single cylinder gasoline engine on a variety of expansion chambers to determine the effect of inlet/outlet locations on higher order mode propagation. Higher order mode excitation was evaluated for a variety of chamber diameters, outlet offsets, combined inlet and outlet offsets, and inlet and outlet angular positions. The (0,1) first symmetric mode and (0,2) second symmetric mode appeared to be excited in chambers with inline inlet/outlet locations and an expansion ratio greater than about nine. The (0,1) mode could be eliminated when the outlet was positioned on the pressure nodal circle of the (0,1) mode. Offset of the inlet and outlet appeared to excite the (1,0) first asymmetric mode. This mode could be eliminated by rotating the inlet and outlet to an angular separation of 90°. This configuration appeared to excite the (2,0) second asymmetric mode.
Noise-induced shifts in the pitch of pure and complex tones
Authors: Houtsma Adrianus J. M.
Published: October 2005

Pitch-matching experiments were performed between test sounds comprising dichotic harmonic two-tone complexes or single harmonics, both partially masked by lowpass noise, and a diotic periodic pulse comparison sound. Tones were at 60 dB SPL, and the pitch of the test signal was measured as a function of the intensity of the masking noise. The slope of the resulting pitch functions, expressed in percent pitch shift per dB of noise, was measured for several harmonics and two-tone complexes, all having a fundamental of 200 Hz. Measurements were also obtained for harmonics in contralateral lowpass noise. Slopes for complex tones were found to be substantially smaller than slopes for pure tones in ipsilateral noise, but about the same as the slopes for pure tones in contralateral noise. This finding is inconsistent with the idea of serial pitch processing (frequency →, spectral pitch → virtual pitch) as found in Terhardt's virtual pitch theory, but supports the notion that pure tone pitch and complex tone pitch are mediated by entirely different mechanisms. [Work supported by NIH, Grant NS11680.]
Interaurally phase/time sensitive cells in the cat inferior colliculus
Authors: Kuwada S. , Yin T. C. T. , Sujaku Y.
Published: October 2005

Using dichotically presented sinusoids, the response of many low-frequency cells in the inferior colliculus (IC) will vary cyclically as a function of the interaural delay. Furthermore, the interval between peaks of this cyclic pattern equals the period of the stimulating frequency, indicating that these neurons are sensitive to changes in interaural phase created by the delays. This is further demonstrated by the use of binaural beat stimuli which yield results similar to those obtained by the interaural delay method. Most IC neurons show an equal amplitude symmetrical cyclic response independent of the magnitude or sign of the interaural delay and rate or direction of interaural phase change. However, we have encountered a sizeable number of cells that are sensitive to the above parameters as well as to the stimulus features such as off-time and interaural intensity differences. These results have been helpful in developing a computer simulated model of a binaural cell. Recently, we have extended our studies to high-frequency IC neurons and have found that under appropriate stimulus conditions they are sensitive to changes in interaural delay in a manner similar to their low-frequency counterparts.
Effects of unilateral lesions in the central auditory system on sound localization behavior
Authors: Jenkins William M. , Masterton R. Bruce
Published: October 2005

Cats with unilateral lesions of the lateral lemniscus, inferior colliculus, brachium of the inferior colliculus, medial geniculate, or auditory cortex were tested behaviorally for their ability to localize the source of a brief sound. In addition, normal cats and control cats with damage either to one ear or to the trapezoid body were behaviorally tested. Cats with unilateral lesions exhibited a deficit in the ability to localize the source of a sound only when the sound source was located contralateral to the side of the lesion. The cats with control lesions exhibited a deficit in the ability to localize the source of a sound irrespective of the sound-source location. The relationship of these results to the representation of auditory space in the central auditory system as well as to recent electrophysiological studies will be discussed. [Work supported by grants NDS00726, NS 10414 and the Coleman Fund.]
Further studies of the discrimination of simultaneous musical intervals
Authors: Zatorre Robert J.
Published: October 2005

Experiments were undertaken to measure unbiased discriminatory ability and to examine the role of interference in discrimination of musical intervals. A continuum was constructed where the bottom tone remained fixed and the top tone varied in pitch so as to form intervals between a minor and major third. Pairs of intervals from the center and ends of the continuum were presented in a two-interval forced choice task to seven musically trained listeners. There were three interference conditions: either silence, low-pass filtered noise, or a tone were interposed between the two stimuli to be discriminated. Results showed large peaks in discriminability for stimuli from the center of the continuum, much as in speech perception. Tone interference lowered overall performance while leaving the shape of the function unchanged. Noise interference had no appreciable effect. These results support the existence of two types of information: auditory and symbolic (i.e., labeling). However, new data suggest that contextual factors may also be important in that the location of the peak appears to depend on the length of the continuum.
Acculturation and psychological adjustment of perception and discrimination of listener in performance of tempered tuning of fixed pitch musical instruments
Authors: Mulder George W.
Published: October 2005

Some recent psychological approaches have begun to examine responses in terms of the effects of intervalic tunings and discrimination by performer and listener of variable and fixed pitch musical instruments. This has led to the author's survey of selected responses by artist-teachers and students at the Interlochen Center for the Arts of temperament and tuning expectations and the differential limens experienced by the listener. The results of these temperament observations seem to agree closely with earlier studies of the psychological adjustment and acculturation inherent in tuning practices.
Developmental differences in detection and identification of CV syllables
Authors: Longinotti Cheryl S. , Elliott Lois L. , Meyer Dianne
Published: October 2005

This study investigated the detection and identification of synthesized CV syllables [bɑ, dɑ, gɑ] by 6- and 10-year-old children and adults. Detection thresholds were measured using a three-interval forced-choice, adaptive procedure, with trial-by-trial feedback. Syllable identification was measured using a three-alternative forced-choice task, also with trial-by-trial feedback. Performance-intensity functions for the syllable identification data were fit with a logistic function to determine slope and identification thresholds. Detection thresholds and identification thresholds were significantly poorer for 6-year olds than for 10-year olds and adults; performance-intensity function slopes were significantly more shallow for 6-year olds than for the other groups. The effect of syllable was significant for identification threshold and slope, but not for detection threshold. These results extend previous demonstrations of developmental differences in pure tone sensitivity and word identification to CV syllables. [Work supported, in part, by NSF.]
Perception of filtered speech by hearing-impaired listeners and by normal-hearing listeners with simulated hearing loss
Authors: Milner P. , Braida L. D. , Durlach N. I.
Published: October 2005

Six subjects have participated in a study to determine the relationship between actual and predicted performance-intensity functions for nine conditions of high-pass, low-pass, and band-pass filtered speech. Three subjects have bilateral sensorineural hearing loss of varying degrees and etiology, one subject has a unilateral sensorineural loss and two subjects have normal hearing. All subjects were trained and tested on 72 consonant-vowel syllables recorded by two male and two female talkers. Each of the nine filtered conditions (as well as the unfiltered speech) was tested at a minimum of five different levels. Hearing loss in the normal-hearing subjects was simulated by using spectrally shaped wide-band noise to create masked thresholds similar to those of the hearing-impaired subjects. Measured intelligibility scores are compared with the predictions of Articulation Theory using modifications developed by Dugal, Braida, and Durlach [in Acoustical Factors Affecting Hearing Aid Performance and Measurement, edited by Studebaker and Hochberg, (1980)] [Research supported by NIH.]