bluuebunny/crossref_metadata_2025 huggingface dataset:
Scattering from a sinusoid: derivation of linear equations for the field amplitudes
Authors: DeSanto John A.
Published: October 2005

The problem of constructing the scattering field for plane-wave incidence on a sinusoidal surface is considered. Above the highest excursion of the surface the scattered field is written in the usual way as a superposition of upgoing and decaying waves. Linear equations are derived for the coefficients of these waves. Both soft and hard boundaries are considered, as well as arbitrary incidence angle. The equations for the soft boundary condition are similar to those of Uretsky, but the derivation is simpler. The full results for the hard boundary condition are apparently new.
Discrimination of speech sounds by the chinchilla: steady-state /i/ vs /a/
Authors: Burdick Charles K. , Miller James D.
Published: October 2005

Two female and two male talkers recorded two tokens of /a/ and /i/ at each of three pitch levels. Four chinchillas were initially trained to respond differentially to single tokens of one talker's vowels. Intensity was randomly varied over 10 dB throughout. Thereafter variations of tokens, talkers, and pitch levels were singly introduced, and performance exceeding 90% correct was maintained. When the full catalog of 24/a/'s and 24/i/'s was used, performance fell to 86% correct. The decrement appeared to be related to testing variables rather than the animals' abilities. The testing procedure was modified and performance rose to 95% correct. Generalization tests showed that the animals could easily transfer to a set of 24 new talkers as well as to synthetic vowels that differed in only formant locations. The chinchilla can correctly classify novel instances of /i/ and /a/ in spite of variations from tokens, talkers, pitch levels, and intensity. [Supported by NIH Grants NS03856 to CID and RR00396 to the Biomedical Computer Laboratory of Washington University.]
Perceptual identification of voices under normal, stress, and disguised speaking conditions
Authors: Hollien H. , Majewski W. , Hollien P. A.
Published: October 2005

A number of authors have contended that, at present, the human auditor is the most accurate “system” for correctly identifying speakers from tape-recorded materials; other authors have indicated that individuals do not have to know the speakers in order to make highly accurate judgments of this type. This research attempts to test these two assumptions. Talkers were 10 adult males who read a modernization of R. L. Stevenson's “Apology for Idlers” under three conditions: (a) normal speech, (b) stress (talkers were subjected to randomly distributed electric shocks while speaking), and (c) disguised speech. Three types of listeners were utilized: (a) listeners who knew the talkers, (b) listeners who did not know the talkers but who were native speakers of English, and (c) listeners who knew neither the talkers or the language (i. e., native speakers of Polish who did not know English). The listeners who knew the speakers scored very high for all speaking conditions, nearly 100% for both normal and stress and 79% for disguise. The scores for the English-speaking listeners, who did not know the speakers, were about one-half as high (even after training) as those for the first group for both normal and stress and were poorer by a factor of three for the disguised condition. Scores for the listeners who knew neither the talkers nor the language were lower than for the other groups but patternings among the data were the same. Implications of these results are discussed.
Dichotic verbal transformations: evidence of separate neural processors for identical stimuli
Authors: Warren Richard M. , Ackroff John M.
Published: October 2005

When a word or phrase heard monaurally or diotically is repeated over and over without pause, perceptual organization becomes unstable, and verbal transformations (VTs) to other words or phrases occur [see Warren, Psychol. Bull. 70, 261–270 (1968)]. We have extended study of this illusion to dichotic conditions. When each ear is presented with a different repeated word, CTs were found to occur on each side in a seemingly independent fashion. What if a single stimulus were presented dichotically with a delay of a few hundred milliseconds separating the arrival of the identical input at the two ears and preventing fusion into a single auditory image? Successive utilization of the same neural units for processing would produce the same VTs on each side, but independent lateral changes would indicate different processing centers for identical stimuli. Independent CTs were found for all 20 subjects: for example, the stimulus word “tress” might be heard correctly on one side, while the transformed word “tramp” was heard clearly on the other. Comparison of the rate and kinds of VTs for the right and left sides has produced information concerning the relative behavior of the separate analyzers.
Successful speech compression use by blinded veterans
Authors: De l'Aune W. R. , Nelson J. L. , Needham Waiter E.
Published: October 2005

The Subjects (36 blinded veterans) were asked to listen to four sections of a seventh-grade-level biographical sketch which had been recorded at progressively faster rates (1.0, 1.5, 2.0, and 2.5 times the initial rate of 194 words per minute) through use of a commercially available electronic discrete time compressed speech device. After each section (approximately 847 words), multiple-choice questions were asked. The highest rate at which 60% were answered correctly was taken as the maximum comprehensible compression rate (MCCR) for that subject. It was found that 53% of the veterans tested could meet the criterion level of comprehension at the 2.5 compression rate. Variables such as age, use of hearing aid, education level, Wechsler Adult Intelligence Scale Verbal IQ, average monthly talking book use, brain damage, extent of visual impairment, response to the speech compression (liked or disliked), and scale scores of the Minnesota Multiphasic Personality Inventory (MMPI) and the California Psychological Inventory (CPI) were analyzed for possible relationship with the Subject's MCCR. Results indicated that younger veterans whose personality tests indicated better psychological adjustment tended to be more successful in comprehending compressed speech.
Effects of signal and masker durations and experimental paradigm on detection under diotic and dichotic listening conditions
Authors: Trahiotis C.
Published: October 2005

Detection efficiency was assessed under diotic (N0S0) and dichotic (N0Sπ) conditions for various signal and masker durations utilizing one- and two-interval forced-choice procedures. Performance under dichotic conditions was severely degraded when signals and maskers were short and simultaneous. When signals and maskers began together and maskers terminated up to 120 msec after signal offset, performance was degraded under both binaural configurations compared to performance in continuous noise and when signal and maskers were simultaneous and equal in duration. Detectability was also found to be differentially effected under the two binaural conditions when short (10 or 20 msec) signals were placed at the beginning, middle, or at the end of the maskers of 100- or 200-msec duration. The degradations of performance related to signal and masker duration were found to interact with experimental paradigm.
Comparison of duration effects in homophasic and antiphasic tonal detection
Authors: Ermey Harold L.
Published: October 2005

Psychometric functions were obtained for detection of 500-Hz sinusoidal pulses masked by continuous wide-band Gaussian noise. Pulse durations were 0.1, 0.2, 0.5, and 1.0 sec for each of four interaural conditions—two homophasic (N0−S0 and Nπ−Sπ) and two antiphasic (N0-Sπ and Nπ-S0). As signal duration was increased from 0.1 to 1.0 sec, the decrease in signal level necessary to maintain constant detection was about 2 dB greater in the homophasic than in the antiphasic conditions. This reduction in the masking-level difference with increasing signal duration was confirmed in a follow-up study using pulse durations of 0.2, 1.0, and 4.0 sec.
Measurement of the interaural amplitude threshold for a 500-Hz tone
Authors: Leshowitz B. , Zurek P. , Ricard G.
Published: October 2005

In order to preclude changes in monaural loudness from serving as a cue in the discrimination of interaural amplitude, the amplitude of binaurally presented tone bursts was varied randomly across observation intervals. Subjects were required to discriminate a change in interaural amplitude and to disregard the overall level of the tones. In contrast to previous data reported by Hershkowitz and Durlach [J. Acoust. Soc. Am. 46, 1464–1467 (1969)] for a constant-amplitude condition, interaural amplitude sensitivity decreased markedly as the interaural amplitude ratio decreased from unity. That observers can still detect an interaural amplitude difference of 4.0 dB with interaural amplitude ratios of 30 dB implies that binaural mechanisms, not monaural alone, must be postulated to explain this performance. In a second study, the effects of masking noise on interaural amplitude discrimination were investigated. Whereas the addition of noise to one ear did not increase the interaural phase threshold, the interaural amplitude threshold deteriorated rapidly upon addition of a monaural noise. The addition of a binaural in-phase noise to the signal, producing a correlated noise condition, markedly improved interaural amplitude sensitivity relative to the monaural masker condition.
On the peripheral encoding and pitch strength of complex tones
Authors: Hall J. W. , Soderquist D. R.
Published: October 2005

Complex pitch perception in the human auditory system was examined with respect to level of neural analysis and pitch strength of various complex tones. In binaural conditions, three-component complex stimuli were presented to each ear in such a way that if information from both ears were mediated centrally, one pitch would be perceived. If pitch were analyzed peripherally, two pitches would be perceived. Two pitches were perceived and peripheral encoding was supported. Subjects judged the strength of monaurally and binaurally presented stimuli which varied with regard to spectral region of the components, number of components per complex, and spacing between components. Pitch strength results were found to be in agreement with Wightman's autocorrelation model of pitch strength [“The Pattern Transformation Model of Pitch,” J. Acoust. Soc. Am. 54, 407–416 (1973)].
Deflection of a plane wave by an oscillating wall and the one-dimensional sound field in a duct with one rigid and one oscillating termination
Authors: Hwang Yun-Fan , Tichy Jiri
Published: October 2005

As a part of the Pennsylvania State University research program on the effect of a moving boundary on the sound field in reverberation chambers, a theoretical model consisting of a parallelopiped with one wall oscillating at large amplitude has been developed. In this paper, the first part of the study is presented. Equations for the reflection of the plane monochromatic wave (ω0) perpendicularly incidenting on an oscillating wall (Ω) using transformation of the coordinate system in the moving wall were derived. The reflected wave has a line spectrum represented by ∑ n=−∞∝ An exp{− i [(ω0 ± nΩ) − ky]}. The method of calculating An is presented. A further step consists of a study of the sound field in a finite-length duct, with one termination oscillating at large amplitudes and the other reflective.
Role of articulator factors in phonological development
Authors: Molfese Dennis L. , Dunckley Candida
Published: October 2005

Menyuk (1971) has argued that a child's misarticulations are the result of his failure to discriminate certain acoustic cues. In light of more recent studies which demonstrate sophisticated speech perception abilities in infants, Palermo and Molfese (1972) have argued that children's errors are due to articulatory rather than acoustic factors. The following study attempted to assess the role of articulatory factors in the development of speech production. Children between three and seven years of age were asked to repeat words containing one, two, and three consonants grouped in clusters. Pronunciation errors were analyzed. A linear relationship was found between the number of consonants in a cluster and the number of imitation errors produced by the children at different ages. In addition, the number and size of these errors increased as a function of the horizontal and vertical place of articulation for these consonant sounds. These findings are discussed as supporting the notion that articulatory rather than acoustic mechanisms are the main factors influencing phonological development in children.
Pressure-referenced analysis of the acoustic properties of speech
Authors: Agnello Joseph G. , Weiler Ernest M. , Howard Merle
Published: October 2005

Previous research by Lisker and Abramson [L. Lisker, and A. S. Abramson, “Cross Language Study of Voicing in Initial Stops: Acoustical Measurements,” Word 20, 384–422 (1964)] report measurements designated voice onset time (VOT). VOT has been shown to be reliable in distinguishing consonant cognates and also differences across languages. More recently, Stevens and Klatt [K. N. Stevens and D.H. Klatt, “Role of Formant Transitions in the Voiced-Voiceless Distinction for Stops,” J. Acoust. Soc. Am. 55, 653–659 (1974)] have noted that the voice bar and the formant transitions are traded off as the distinguishing acoustic feature in the perception of the step consonants. A new method allows for VOT equivalency measurements and a new measure designated as voice termination time. The technique simultaneously records intraoral air pressure and spectrographic speech analysis through a sonagraph. The time from peak pressure to formant onset or from formant offset to peak pressure yields measures of VOT and VTT, respectively. Air pressure can be more reliably recorded than voice bar or aspirant spike, especially for VTT measures. Comparative procedures and data are discussed for acoustic perception of “b” and “p” phonemes.
Differences in the P3 component of the cortical evoked potential elicited by syllables and pure tones
Authors: Schulman C. A. , Smith T. S. , Benson P. J. , Osier H. , Galambos R.
Published: October 2005

Hemispheric asymmetries of the cortical evoked potentials in response to speech stimuli have been reported by several laboratories. The present experiment sought to determine whether a paradigm which elicited the P3 wave, which occurs when the subject attends to an infrequent stimulus, would enhance such differences. Eight subjects listened to four sets of stimuli, two consisting of the CV syllables /pa/ and /ba/, and two consisting of pure tones at 250 Hz and 600 Hz. Each stimulus appeared as the frequent and infrequent stimulus, in a ratio of 1:4, in one of the sets. The subjects' task was to count the infrequent stimulus in each set. Separate averaged evoked responses were computed for each of the four conditions, from recording sites at the vertex and homologous points over the right and left temporal areas. The P3 waves elicited by the infrequent stimuli differed considerably between conditions (speech or tones) but within-condition asymmetries between the temporal area electrode sites were not observed.
Frequency specificity of brainstem evoked responses in man
Authors: Hecox K.
Published: October 2005

This report extends previous observations on the acoustical dependencies of human brainstem evoked potentials. We report here on the effect of filtered continuous-noise maskers on the latency and amplitude of click evoked responses. In condition 1, the masker high-frequency cutoff is fixed at 20 kHz, while the low-frequency cutoff varies from 16 to 0 kHz. Progressively extending the low-frequency cutoff produces a decrease in amplitude and an increase in latency of wave V, the most reliably elicited response component. The response is abolished when the low-frequency cutoff is at 2 kHz. In condition 2, the low-frequency cutoff of the masker is fixed at 0 kHz while the high-frequency cutoff is varied from 0.5 to 20 kHz. No latency or amplitude changes appear until the high-frequency cutoff reaches 4 kHz, and the response is abolished at high-frequency settings between 8 and 16 kHz. These experiments demonstrate that click-evoked brainstem responses are generated by high- and middle-frequency fibers, with very little contribution from low-frequency fibers. The latency and amplitude shifts described above do not correlate well with the subjective threshold changes produced by the various maskers, but are better explained on the basis of traveling wave delays at the cochlear level.
Further studies of “effective quiet.”
Authors: Ward W. D. , Cushing E. M.
Published: October 2005

Earlier results [W. D. Ward, J. Acoust. Soc. Am. 54, 327 (1973)] indicated that an absence of interference with the process of recovery from TTS produced by bursts of an octave band of noise centered at 4 kHz occurred only if the level of the intervening noise (also 4 kHz) was 55–60 dB SPL or lower. Subsequent experimentation using 10 normal-hearing young listeners has confirmed this rather low value of effective quiet for this particular octave band. However, for both 1- and 2-kHz octave bands, effective quiet is reached at 70 dB SPL, and for 500 Hz at 75. It appears, therefore, that neither A- nor D-weighting will adequately represent the relative noxiousness of different octave bands using this particular criterion of hazard. [Research supported by the National Institute for Occupational Safety and Health, Public Health Service.]
Applications of modern transducer principles
Authors: Sessler G. M. , West J. E.
Published: October 2005

A discussion of piezoelectric polymer, ceramic, and electret materials and transducer principles will be presented. Applications of these transducers in a variety of fields, such as audio and ultrasonics (microphones, earphones, and phonograph cartridges), gas analysis, data transmission, and telephony will also be discussed.
Signal-processing gain by digital beamforming in Doppler sonar
Authors: Wang H. S. C.
Published: October 2005

The signal-processing gain by digital beamforming in Doppler sonar was investigated in terms of the enhancement of signal-to-reverberation ratio (SRR) at the post-beamforming Doppler filter output with an objective to determine the minimum number of bits necessary for the quantization of beamformer channel input signals without appreciable degradation of sonar performance. It is shown that, in the present case, the simplified method of counting spectral lobes originally due to Davenport [W. B. Davenport Jr., J. Appl. Phys. 24, 720 (1953); for application to multichannel multibit signal processors, see H. S. C. Wang, J. Acoust. Soc. Am. 53, 929 (1973)] can only be applied with certain modifications in the evaluation of various signal and reverberation interacting power terms. Extensive numerical calculations of “Doppler processing gain” were then carried out to demonstrate that four-bit quantization of array transducer signals is theoretically sufficient to yield a performance essentially identical to that of a linear beamformer, but severe loss of gain could result if fewer than four bits are taken at the quantizer output. It is further demonstrated numerically and substantiated analytically that, for small input SRR, the processing gain of a digital beamformer with Doppler filters cannot exceed that of a linear (or optimized four-bit digital) beamformer even if its channel signals are quantized into more than four bits.
Analysis of vibrations of rectangular plates with edges elastically restrained against rotation using simple polynomial approximations
Authors: Laura P. A. A. , Romanelli E.
Published: October 2005

The analysis of vibrating plates with edges elastic. ally restrained against rotation is of interest in many engineering situations since perfect supports or clamps constitute, in general, ideal limiting conditions. The present paper deals with the calculation of some of the lower natural frequencies of a rectangular plate having w = 0 and uniform slope restraint along pairs of opposite edges. The plate is subject to uniform, in-plane tensile stresses Nx, Ny and the mode shapes are approximated by simple polynomials which identically satisfy the boundary conditions. The procedure is simple and straight-forward, and accurate frequency expressions are obtained by means of the Galerkin method. It is important to point out that as the rotation boundary parameters φx, and/or φy approach zero, one obtains expressions corresponding to ideal clamps. On the other hand, if φx, and/or φy approach infinity, the expressions degenerate properly into those corresponding to simple supports.
Nonlinear electroelastic equations for small fields superposed on a bias
Authors: Baumhauer J. C. , Tiersten H. F.
Published: October 2005

The nonlinear differential equations and boundary conditions in small-field variables, for small fields superposed on large static biasing states, are obtained from general rotationally invariant nonlinear electroelastic equations derived previously. The small-field equations are directly applicable in the consistent description of parametric effects in high-coupling piezoelectric materials in terms of the fundamental material parameters. The application of the equations to homogeneously polarized ferroelectrics reveals that in the linear limit the electroelastic equations are identical with the equations of linear piezoelectricity for the symmetry of the polarized state. The influence of a thickness directed homogeneous biasing electric field on the thickness vibrations of a piezoelectric plate, to second order in the biasing field, has been determined. To first order in the biasing field the results indicate that the effective fifth-rank tensor assumed in earlier quasilinear work on the subject did not have correct symmetry properties because the influence of the homogeneous static deformation under the biasing field was ignored.
Interruptibility of speech
Authors: Ladefoged P. , Silverstein R. , Papçun G.
Published: October 2005

Experiments were conducted on the ability of a speaker to interrupt himself when given a cue to do so at unexpected moments. There seems to be no particular point in an utterance when a speaker finds it harder to stop saying what he originally intended to say and start saying something else instead. Just before an utterance, while a speaker is planning the articulations, there is a period during which he cannot readily plan another utterance, but he can perform nonspeech gestures.
Sound insulation at low frequencies
Authors: Mulholland K. A. , Lyon R. H.
Published: October 2005

The transmission of airborne sound between two rooms coupled by a panel is investigated. At low frequencies individual modes in the rooms and the panel control the transmission. It is shown that resonant modes in the room are the chief cause of frequency-dependent variations in low-frequency sound insulation. When the reception room has a dominant resonant mode the insulation is small or even negative. Similar behavior occurs when the panel has a dominant resonance but these effects occur at very low frequencies and if the panel is damped may not occur at all. A method is described by means of which the probable behavior of a given panel/room system can be predicted. General conclusions about the likely behavior of panels constructed of a range of materials are given.
Frequency discrimination in the presence of another tone
Authors: Leshowitz Barry , Cudahy Edward
Published: October 2005

The effects of an interference tone on frequency discrimination of a brief tonal signal were investigated. The interference tone was 500 msec in duration and the same intensity as the signal. Changes in frequency discrimination were measured as a function of signal duration, the frequency separation between the interference tone and signal, and the temporal delay between the two. Both ipsilateral- and contralateral-interference conditions were investigated. The addition of an interference tone significantly degraded preformance in only one condition: 10-msec signal, trailing interference tone delivered to signal ear. For all other stimulus configurations, frequency discrimination was unaffected by the presence of the interference tone. These data are generally consistent with analogous sensory masking effects characterizing backward and forward masking and do not support cognitive-perceptual models of pitch and recognition.
Impedance tube measurement of propagation constant and characteristic impedance of porous acoustical material
Authors: Yaniv Simone L.
Published: October 2005

In this paper an impedance tube technique is described and evaluated for the measurement of the characteristic impedance and propagation constant of porous acoustical materials. In this method, data are determined under dynamic conditions through the investigation of the standing wave patterns existing in a tube driven at one end by a sound source and terminated at the other end by (1) a sample backed by a rigid wall; (2) a sample backed by an air space, a quarter-wave long, itself terminated in a rigid wall. The validity of the method is assessed by comparing values of characteristic impedance and propagation constant for Owens Corning Fiberglas, type 705, density 6 lb/ft3, obtained in this way to values obtained by two other well-known techniques: Beranek's method and Scott's method. Data were obtained at 800, 1200, and 1600 Hz. The analysis performed on the data obtained by the impedance tube technique and Beranek's method are in agreement at all frequencies. Comparable analyses on the data obtained by Scott's method show agreement with data obtained by the other two techniques only for values of the propagation constant at 1200 Hz and 1600 Hz. The discrepancies observed are attributed to experimental difficulties inherent in Scott's method.
Effects of intense auditory stimulation: hearing losses and inner ear changes in the squirrel monkey. II
Authors: Hunter-Duvar Ivan M. , Elliott Donald N.
Published: October 2005

Five squirrel monkeys were exposed to pure tones at intensities and durations sufficient to produce permanent threshold shifts (PTS s). One animal was exposed to a 1 kHz tone at 130 dB SPL for 4 h. Two were exposed to a 1 kHz tone at 140 dB SPL, for respectively, 3 and 4 h. Two were exposed to a 2 kHz tone at 140 dB SPL, for respectively, 3 and 4 h. Pre- and post-exposure behavioral testing was similar to that described in an earlier study (Hunter-Duvar and Elliott, 1972). Following the exposure, testing was carried out at frequent intervals until recovery was no longer evident. Final thresholds were then determined. Animals were next sacrificed, their cochleas were fixed, and surface specimens prepared. Using a phase microscope, missing and severely damaged hair cells (those with fractures of the cuticular plate and obviously displaced nucleii) were determined for each of the inner and outer rows from a point 1 mm from the apex to a point 19 mm from the apex. Hair cells were inspected at all levels. Wide variations in hearing losses and hair-cell damage were found, and were uncorrelated. Hearing losses ranged from less than 20 dB to greater than 50 dB; hair-cell damage ranged from no apparent damage to complete loss of outer and moderate loss of inner cells. Little if any correlation was found between exposure-tone characteristic (frequency, intensity, duration) and hearing loss or hair-cell damage.
Test and evaluation of a quiet helicopter configuration HH-43B
Authors: Bowes Michael A.
Published: October 2005

A series of noise control modifications was made to the HH-43B helicopter. Modifications were made to the aircraft engine, drive, and rotor systems. Significant reductions were achieved in all octave bands of interest, i.e., 63 Hz to 4 kHz, with an average reduction exceeding 8.5 dB. A total of ten distinct aircraft configurations were tested and their respective noise control modifications evaluated. Greatest reductions in noise resulted from engine and rotor system modifications. Turbine engine noise reductions were obtained through the use of reactively lined inlet and exhaust silencers. Rotor system modifications included blade geometry changes and reduced tip speed.
Rhythmic units and syntactic units in production and perception
Authors: Lehiste Ilse
Published: October 2005

It has been claimed that spoken utterances consist of isochronous rhythmic units (metric feet), lasting from one major stress to the next. A study of 17 specially constructed sentences showed that productions of the same metric foot types have remarkably similar durations. However, there are clear differences in the average duration of different foot types in the same position, and there is neutralization of durational differences in final position. The partial isochrony found in the study leads to two further questions: the influence of syntax on the production of rhythmic units, and the perceptual nature of isochrony. If rhythmic units are independent of syntactic structure, sentences consisting of the same lexical items should have the same temporal structure regardless of syntax. A study of syntactically ambiguous sentences showed that they can be successfully disambiguated by adjusting the rhythmic units to reflect syntactic structure. The hypothesis that isochrony is primarily perceptual was tested by having 30 listeners first judge the duration of metric feet in the 17 analyzed sentences and then perform the same task with nonspeech stimuli consisting of sequences of noise bursts and noise-filled intervals duplicating the rhythmic structure of the sentences. Listener performance was significantly better in the second test, suggesting that isochrony may indeed be at least partly a perceptual characteristic of spoken English.
The effect of position in utterance on speech segment duration in English
Authors: Oller D. Kimbrough
Published: October 2005

The duration of speech segments as a function of position in utterances (initial, medial, final) was studied. In the first experiment seven English speakers read nonsense utterances of the form “say a [bab], say a [bábab], say a [babáb],” etc. Spectrograms were used to determine the duration of speech segments in the readings. Final syllables were found to be longer than nonfinal syllables. Final-syllable vowel increments were approximately 100 msec. Final-syllable consonant increments were less than vowel increments; for instance, absolute final consonant increments were about 20 msec. Also word-initial consonants were found to be lengthened by 20–30 msec over medial consonants. Subsequent experimentation demonstrated with English nonsense words that (1) final-syllable and initial-consonant lengthening occur in utterances with various intonational patterns (imperative, declarative, interrogative); (2) final-syllable lengthening occurs in word-final and phrase-final positions as well as in utterance-final position; and (3) final-syllable and initial-consonant lengthening occur in various kinds of syllables, including syllables with diphthongs, with fricative consonants, with voiceless stops, with consonant cluster, and with no final consonants (i.e., CV syllables). These studies report durational increments of particularly great magnitude for absolute final fricative consonants. Explanations of the lengthening effects are discussed. One theory suggests that lengthening in certain utterance positions is a learned aspect of language which cues listeners concerning the location of boundaries of words, phrases, or sentences. Explanations based on hypothesized properties of the speech production process are also discussed.
Finite element analysis of acoustically radiating structures with applications to sonar transducers
Authors: Smith R. R. , Hunt J. T. , Barach D.
Published: October 2005

A numerical technique for mathematically modeling the vibrational response of a complex structure immersed in an infinite acoustic medium is presented. The elastic response of the structure is modeled using the finite element method, and the acoustic radiation loading on the structure is modeled by approximating the surface Helmholtz integral equation formulation of the acoustic radiation problem. Arbitrary (and distinct) nodal point distributions and interpolation functions can be used in the finite element and acoustic radiation models. A technique defined in terms of these nodes and interpolation functions is presented for combining the results of these models into a combined equation of motion for the acoustically damped structure. The application of this technique to sonar transducers is discussed, including the modeling of piezoelectric material. The problem of obtaining reliable piezoelectric material parameters is discussed. Mathematical models are given for a piezoelectric sphere, a piezoelectric free-flooded cylinder, and a coaxial array of two cylinders. In general, comparison of numerical and experimental results (electric impedance plot, transmitting voltage response, beam patterns) for these devices agree within 5%. Results for the coaxial array exhibit somewhat more error.
Spatial correlation in arbitrary noise fields with application to ambient sea noise
Authors: Cox Henry
Published: October 2005

Explicit expressions are developed for the cross-spectral density between pairs of sensors and the wavenumber-frequency spectrum projected onto the line joining these sensors, when they are placed in arbitrary positions in noise fields which are described by an arbitrary directional distribution of uncorrelated plane waves. The approach is to expand the directional distribution in spatial harmonics. Each harmonic leads to a corresponding term, with the same coefficient, in series representations for the cross-spectral density function and the wave-number-frequency spectrum. The approach particularly attractive when the field can be adquately represented by a relatively small number of harmonics. Both two- and three-dimensional fields are considered. The approach is applied to the vertical directionality of ambient sea noise and is related to some existing models of ambient sea noise. Some new models are presented. Results are compared with reported experimental data and found to be in good agreement over a wide frequency range.
Perturbation of plant-cell contents by ultrasonic micro-irradiation
Authors: Gershoy Alexander , Nyborg Wesley L.
Published: October 2005

An account is given of mechanically induced disturbances in a vacuolate plant cell when part of its wall is set into low-amplitude vibration at ultrasonic frequencies. Beginning at vibration amplitudes ξ0 in the vicinity of 0.1 μm distortions of the vacuolar membrane occur. These take the form of evaginations into the vacuole; it is proposed that they result from flow of fluid along the parietal channel. The rate of growth of evaginations is in order-of-magnitude agreement with simplified theory, in which it is assumed that the flow arises from gradients of radiation pressure. Continued sonation at an amplitude of about 0.2 μm leads to rupture of the vacuolar membrane and fragmentation of the cytoplasm; plastid-containing fragments are then released into the vacuole. Motions in the vacuole include acoustic microstreaming as well as particle migrations believed to result from radiation pressure. Spinning motions are also seen, and are ascribed to acoustic radiation torque. Considerable variation is seen in post-irradiation response. While some cells die after sonication in which no viable changes were seen, others show a surprising ability to recover from apparently severe destruction.
Echolocation: high-frequency component in the click of the Harbour Porpoise (Phocoena ph. L.)
Authors: Møhl B. , Andersen S.
Published: October 2005

Besides the already known low-frequency components of the Phocoena echolocation pulse, a narrow-band pulse of 0.1-msec duration, with the main energy between 110 and 150 kHz and a source level of 40 dB re 1 μbar at 1 m has been found. The properties of this pulse can explain how wires below 1-mm diam can be detected by echolocation. The results are consistent with the hypothesis that the emission is restricted to a narrow beam.
Consequences of peripheral frequency selectivity for nonsimultaneous masking
Authors: Duifhuis H.
Published: October 2005

The frequency selectivity of the peripheral ear (e.g., at the VIIIth nerve level) is so acute that onset and offset transients in responses to short signals produce a nonnegligible extension of the signal duration. Thus, peripheral excitation patterns produced by signals which were separated in time can overlap and thereby mask each other. We refer to this type of masking as transient masking. Published data on nonsimultaneous masking and the results of two new experiments are compared with the masking that may be expected from filter transients. It is concluded that backward masking is mainly due to interactions at the level of the filter outputs, and that in forward masking, in addition to a short-term component, a long-term component is distinguishable. The latter has an exponential decay with a time constant of approximately 75 msec, and is probably related to physiological adaptation effects.
Recovery from sound exposure in auditory-nerve fibers
Authors: Young Eric , Sachs Murray B.
Published: October 2005

The discharge rate of single auditory-nerve fibers to tone bursts was measured after exposure to continuous tones. Both the exposure tone and the test tone bursts were at the fiber's characteristic frequency. Following exposure, the discharge rate to the test bursts is transiently depressed. For moderate exposures (180 sec or less in duration and less than 80 dB SPL), the recovery of discharge rate to the preexposure level is well described by a single rising exponential. The time constant of the recovery increases as the level or duration of the exposure increases; time constant decreases as the level of the test bursts is increased. For all exposure and test conditions employed, time constants were in the range 1–30 sec. The relevance of these data to hypotheses about the mechanisms of adaptation in the auditory periphery is discussed.
On the mechanism of sound production in organ pipes
Authors: Elder Samuel A.
Published: October 2005

It is shown that both the Cremer-Ising and Coltman mechanisms for sound production in organ pipes are comprehended by a more general approach, based on conservation of linear momentum. By calculating force per unit area exerted by the jet on a control volume containing the mixing region, and equating this to the difference in pressure along the pipe axis, it is possible to derive an expression for acoustic particle velocity in the standing wave as a function of the jet driving flow spectrum. The momentum model of the jet-pipe interaction is able to explain the Coltman radiation symmetry effect, and also accounts for the role of entrained air in sound production. Additional spectral interaction terms, not previously noted, are found to play a significant role in the production of sound-pressure fluctuations in the pipe. The fluctuating lift force at the edge is found to contribute to the sustenance of the pipe-cavity oscillation below resonance, opposing it above resonance. In the near vicinity of the resonant frequency, edgetone effects are relatively small.
A model for vocal cord excitation
Authors: Gupta V. , Wilson T. A. , Beavers G. S.
Published: October 2005

This paper reports the results of an experimental and analytical investigation of a possible mechanism for exciting vibrations of the vocal cords. In order to test various approximations for describing the flow past the vocal cords and to demonstrate the importance of the upstream impedance in the excitation mechanism, the vocal cords are first represented by the simplest possible model, namely a simple vibrator of fixed shape. It is shown that if the pressures at the upstream and downstream ends of the channel formed by the vibrator wall are constant, the aerodynamic forces take energy from the vibrational motion. If, on the other hand, the output impedance of the system upstream of the channel is negative imaginary, vibrations of the channel walls can be excited. Experimental results agree with the predictions of the flow analysis for the simple vibrator. It is then argued that the respiratory system upstream of the larynx can be described as a tube 20 cm long in which the wave speed is reduced because of the distensibility of the bronchi, and which opens into the large reservoir of the lungs. Results of experiments in which the input impedance at the mouth was measured are consistent with this description. With this upstream impedance it is found that the simple vibrator would only be excited in a limited frequency range and would not allow many of the significant features of the vocal cord vibrations to be represented. Consequently a two-degree-of-freedom model for the vocal cords is introduced. The flow analysis and impedance description are used in calculating the forces acting on the two-mass model. It is predicted from the model that vibrations of the vocal vords are self excited over a range of frequencies. The properties of the self-excited oscillations described by the model agree with the observed properties of the self-excited vibrations in an experiment using a rubber membrane to represent the vocal cord, and are also consistent with several properties of the voice.
Line array performance when the signal coherence is spatially dependent
Authors: Cox Henry
Published: October 2005

The effects of a signal coherence which decreases exponentially with sensor separation are examined for a number of line array processors. For the conventional beamformer the limiting gain against uncorrelated noise as the array is made infinitely long is simply (1 + ρ)/(1 − ρ), where ρ is the signal coherence between adjacent sensors. The gain of the optimum processor is also presented. A simple suboptimum processor which incoherently combines the outputs of a number of subarrays is found to provide near optimum performance. The performance of the split-beam multiplicative processor is shown to degrade rapidly as signal coherence decreases.
Natural motion of a fluid-loaded semi-infinite membrane
Authors: Davies Huw G.
Published: October 2005

Free wave motion on a fluid-loaded semi-infinite membrane whose plane is extended by a rigid baffle is discussed. We consider in particular the membrane displacement field and the associated acoustic radiation when a wave on the membrane is normally incident on the membrane boundary. Typical values for the reflection coefficient for the waves, and for the radiated acoustic power are given for a wide range of membrane in vacuo wavespeeds and fluid loading parameters. It is shown that the commonly used predictions for edge-mode radiation obtained by neglecting the influence of the fluid on the membrane displacement are valid except when the fluid loading is very high.
Sound channel in an exponentially stratified ocean, with application to SOFAR
Authors: Munk Walter H.
Published: October 2005

For much of the World's oceans, the stability of the water column beneath the thermocline is quite well represented by N2(z) = gρ−1 ∂zρ′ = NO2e−2z/B, where ∂zρ′ is the vertical gradient in potential density, NO ≈ 3 cycles/h is the surface-extrapolated “Brunt-Väisälä” frequency, and B ≈ 1.3 km is the stratification scale. This leads to an idealized sound channel C(z) = C1 [1 + ε(η + e−η − 1)] = C[1 + ε(1/2)η2 − (1/6)η3 + …] with a minimum velocity at the axis z = z1, η = (z − z1)/12B being dimensionless depth relative to z1. The parameters ε, z1 are explicitly expressed in terms of the five coefficients α, β, γ, a, b (temperature, salinity, pressure coefficients of C; temperature and salinity coefficients of ρ′), given only the form of N(z) and a representative T, S relation. The up-down asymmetry of the channel, a consequence of the fundamental structure of the oceans, plays a first-order role in the propagation characteristics. As an application, the ray arrivals for an axial source and receiver are computed.
Noise and vibration of resiliently supported track slabs
Authors: Bender Erich K.
Published: October 2005

This paper examines an analytical model of the dynamic response, vibration isolation, and sound radiation of a resiliently supported track slab. Railroad rails are viewed as beams fastened elastically to a slab which is resiliently mounted to a substructure, and the slab is assumed to be a plate of finite width and infinite length. The analysis accounts for several different mechanisms of vibration transmission from the rail to the slab, including structural nearfield, farfield, and coincidence effects. The results show that the slab is a very effective vibration isolator but is a sounding board at low frequencies. Proper choice of rail and slab parameters can make this low-frequency radiation comparable to the low-frequency sound ordinarily generated by an electrically powered rail vehicle.
Finite element approach to acoustic radiation from elastic structures
Authors: Hunt John T. , Knittel Max R. , Barach Don
Published: October 2005

An approximation method is presented for solving the equations of motion that describe the vibration of an elastic structure immersed in an infinite acoustic fluid medium. The mathematical model that is developed uses the finite element method to calculate the vibrational characteristics of the elastic body and the acoustic pressure field of that portion of the fluid which closely surrounds the vibrating body. Analytical methods are used to obtain the boundary conditions for this mathematical model. This technique can be used to predict the response of an elastic structure over a wide range of frequencies and the acoustic pressure at a large number of field points in both the nearfield and farfields. It avoids the difficulties encountered at eigenvalues of the interior problem by determining exactly the one degree of freedom needed to overdetermine the surface equations. Experimental validation of theoretical predictions is given for a piezoelectric cylinder, and a computer-generated contour plot of a predicted nearfield pressure distribution is shown.
Nonlinear analysis of the forced response of structural elements
Authors: Nayfeh Ali H. , Mook Dean T. , Sridhar Seshadri
Published: October 2005

A general procedure is presented for the nonlinear analysis of the forced response of structural elements to harmonic excitations. Internal resonances (i.e., modal interactions) are taken into account. All excitations are considered, with special consideration given to resonant excitations. The general procedure is applied to clamped-hinged beams. The results reveal that exciting a higher mode may lead to a larger response in a lower interacting mode, contrary to the results of linear analyses.
Fifty-four voices from two: the effects of simultaneous manipulations of rate, mean fundamental frequency, and variance of fundamental frequency on ratings of personality from speech
Authors: Brown Bruce L. , Strong William J. , Rencher Alvin C.
Published: October 2005

Utterances of two adults males were analyzed and synthesized by a fast Fourier Transforms method. Each of the two voices was synthesized in each of the twenty-seven combinations of three levels each of rate, mean FØ, and variance of FØ (a total of fifty-four “voices” generated from two). The effects of the rate, mean FØ, and variance of FØ manipulations, the interactive effects of rate and variance of FØ, and the effects due to speaker were all statistically significant predictors of personality ratings given the voices. They accounted for 86%, 4%, 3%, 2%, and I% of the variance, respectively, in competence ratings and 48%, 1%, 6%, 1%, and 8% of the variance, respectively, in benevolence ratings. Increased speaking rate was found to decrease the benevolence ratings, and decreased rate was found to decrease competence ratings. Decreased variance of FØ was found to decrease the ratings on both competence and benevolence. Increased mean FØ in these male voices was also found to decrease competence and benevolence ratings.