bluuebunny/crossref_metadata_2025 huggingface dataset:
Motorboat noise and technology assessment
Authors: Smullin J. I.
Published: October 2005

Motorboat noise, both onboard and remote, from operating motorboats is examined, including standardized procedures for noise measurements, a data base of noise levels from over 500 motorboats, the available technology for engineering noise control techniques, and existing legislation effecting noise emissions from motorboats. In order to support a motorboat noise impact assessment a relationship between full power noise levels, as measured in legislated and engineering society procedures, and partial throttle operation which is representative of the majority of motorboat usage has been determined for each of several categories of motorboats. It is shown that the variance of horsepower weighted noise increases as the responsibility for the propulsion package engineering and manufacturing process for single boat type becomes more widely distributed. Thus the outboard motors show a minimum variance and conventional inboard motorboats show the widest variance. Existing technology for noise control is shown to be effective for reducing noise from presently achieved levels. But, it is shown that hull water interaction noise does create a lower limit of noise, limiting the noise reductions achievable by treatment of motor noise. [Work supported by EPA/ONAC.]
Noise impact assessment of motorboats
Authors: Wright P. J.
Published: October 2005

Motorboating in the U.S. has shown a steady growth over the past two decades to the point where Americans own an estimated 8 500 000 motorboats. The potential impact on the health and welfare of the American population is great. In order to assess this impact, an analytic noise impact assessment model was developed and evaluated. Criteria for impact consist of hearing loss, indoor and outdoor speech interference, and overall annoyance. The model is statistical in nature. Data on source emission levels by motorboat category, source operating characteristics, and usage patterns are combined with transmission path characteristics and population density information relative to source location to generate the statistical distribution of population vs noise level. Different scenarios of contribution of motorboat noise to the A-weighted energy-equivalent day—night sound pressure level as well as the effects of single-event passbys are considered. The methodology for impact assessment is consistent with EPA's benefit assessment procedure. [Work supported by EPA/ONAC.]
The contribution from propeller cavitation to the airborne noise in after spaces on high speed marine vessels
Authors: Gray Leslie M.
Published: October 2005

Propeller cavitation is often overlooked as a source of airborne noise on ships, because it is unusual to have manned spaces in the vicinity of the propellers. However, when design considerations require that berthing spaces be located over the propellers, cavitation can produce severe airborne and structureborne noise problems. These problems are especially severe in high speed or high power craft, where the propellers are heavily cavitating and the vessel structure is fairly light. This paper presents the results of measurements aboard a high speed (35 knots) research vessel which identifies the contribution to structural vibration and airborne noise from propeller cavitation. Predictions of the airborne noise existing in a proposed crew living space on a similar vessel show airborne noise levels to be 25 dB in excess of compartment specs at a similar speed. The mechanism of propeller cavitation and procedures to estimate source strength are reviewed. Relationships are presented to describe the power input to the hull structure from this source, and to describe the airborne sound power resulting from this hull vibration. Procedures for the control of propeller generated airborne noise are outlined, along with some of the unsolved technical problems associated with each of these noise control procedures.
Propagation of aircraft ground run-up noise including the effects of a barrier
Authors: Chessell C. I.
Published: October 2005

Measurements of noise levels generated by an F-111 aircraft during ground run-ups with after-burner are reported. The measurements were made at various azimuths and at ranges out to 2.9 km over open ground and also with the aircraft located behind a 4-m high earth wall. Prevailing meteorological conditions were light winds with both temperature lapse and inversion conditions. The measured noise levels are compared with theoretical model predictions which include the effects of a finite impedance ground, of the meteorological conditions and of the barrier, using the methods of Maekawa [Appl. Acoust. 1, 157–173 (1968)] and Jonasson [J. Sound Vib. 22, 113–126 (1972)] to obtain the diffracted field over the barrier. It is shown that the ground attenuation can be significant out to long ranges but that it may be reduced in part by refraction during downwind propagation. The effects of the barrier are shown to be strong at short ranges but to be negligible at long ranges.
Effectiveness of cylindrically topped noise barriers
Authors: Hayek S. I. , Lawther J. M. , Kendig R. P.
Published: October 2005

Noise barriers having a cross section of a wedge with a cylindrical top is taken as a model for highway berms. These berms are usually covered by vegetation which can be modeled as an absorptive surface. In this study, the noise reduction effectiveness of such noise barriers is assessed as a function of many of the parameters; such as its geometric shape and its acoustic characteristics. The curvature of the cylinder, the interior wedge angle of the sides of the barrier, the acoustic impedance of the barrier's coverage and the location of the highway traffic line from the berm were found to influence the excess attenuation of such a barrier. As the distance between the highway traffic line and the barrier becomes wider, the excess attenuation of the barrier decreases. Similarly, as the curvature of the berm become larger, the excess attenuation increases. The absorptivity of the berm, as modeled by its acoustic impedance, increases the excess attenuation as the berm becomes more absorptive. [Work supported by the National Cooperative Highway Research Program.]
An analysis of traffic noise abatement scenarios
Authors: Cermak G. W. , von Buseck C. R. , Blanchard R. D.
Published: October 2005

Computer simulations of traffic sound levels were performed to evaluate the probable effectiveness of several hypothetical noise abatement scenarios in reducing residential exposure to traffic sound. These simulations were performed for 28 actual census tracts in six cities which were chosen to be representative of the urban United States. Results showed that neighborhood land use patterns have a strong influence on residential traffic noise exposure and thus constrain the potential effectiveness of any noise abatement strategy. Limits on the acceleration noise of new automobiles were calculated to have only a small effect on traffic noise exposure, while limits on truck acceleration noise were calculated to have a greater effect. A combination of noise barriers along freeways and nonresidential zoning along arterials was calculated to have approximately the same effect on residential noise exposure as severe constraints on both automobile and truck acceleration noise levels. Further calculations showed that if no constraints on new vehicle noise levels were imposed, and if the new vehicle fleet included more four cylinder and diesel automobiles, residential traffic noise exposure would be marginally greater than at present.
A comparison between procedures used to locate speech segment boundaries
Authors: Osberger M. J.
Published: October 2005

Locating phoneme boundaries, or “segmenting” the acoustic speech signal, is often necessary in speech research and can be accomplished using different procedures. At the present time, there are little quantitative data on the differences between different methods of segmentation. The purpose of the present study was to compare segmentation data obtained using three different techniques. Speech segment boundaries were located for a set of sentences in the following ways: (1) by eye from digitized waveforms, (2) by eye from digitized spectrograms, and (3) by ear from computer playback of digitized speech samples. Each of the three techniques was employed by three judges who segmented the same set of sentences independently of each other. The data revealed that, on the average, the differences between boundary measurements for the various techniques ranged from roughly 5 to 25 ms. Average measurement differences between the judges ranged from roughly 20 to 35 ms. The magnitude of the differences between the judges varied as a function of phonetic context. [Research supported by PHS Grant 09252, CUNY, and NICHD contract NIH-71-2420 with Haskins Laboratories.]
Comparison of spectral estimate distortions produced by selected data window functions in speech signals
Authors: Riemer T. E. , Cullen J. K.
Published: October 2005

Results of an extensive study of the spectral estimate distortions produced by numerous data window functions [F. J. Harris, IEEE Proc. 60, 51–83 (1978)], including the more common and computationally more convenient functions, are presented. Methods for determining the optimum choice of the parameters of each window are discussed in relation to the signal characteristics, recording system signal-to-noise ratio and frequency response, analog-to-digital sampling and quantizing errors, and computational round-off errors. Spectral estimates for various types of speech signals, including short-duration bursts, for each of the window functions examined are presented and compared. Conclusions are drawn concerning the comparative accuracy of each window with relation to signal and system characteristics. [Work supported in part of NIH.]
A periodicity measure for voiced speech
Authors: Bancroft J. C.
Published: October 2005

There are inherent difficulties in making valid and reliable measures of periodicity in normal and pathological voices. Consequently, this paper presents a new method using computer analysis to measure and quantify periodicity in voiced speech. The measure compares the power between the periodic portion of the voice (the signal) to the power of the uncorrelated aperiodic component of the wave (the noise) and is expressed as a signal-to-noise ratio (SNR). The SNR is basically derived from an autocorrelation pitch detector, that measures the peak amplitude of the autocorrelation function at the pitch period. The SNR also assists in making voiced or unvoiced decisions in continuous speech, and provides a measure between the two extremities for transients and voiced consonants. Typical ranges of the SNR for sustained vowels will be presented for normal and abnormal voices, along with results obtained from continuous speech.
Computer analysis of hoarseness
Authors: Kojima H. , Gould W. J. , Lambiase A.
Published: October 2005

A spectrogram of a normal sustained vowel, taken with a narrow filter, shows well developed harmonics as equally spaced horizontal stripes, while that of a hoarse voice presents noise components as a cloudy shadow between the harmonics. Harmonic components are replaced by noise components as the degree of hoarseness becomes more severe. If the acoustic energy of the harmonics is calculated separately from that of the noise components, the degree of hoarseness can be determined as a ratio of harmonics versus noise, or the signal-to-noise ratio. The harmonic components in a hoarse voice were separated from the noise components using a small laboratory computer. The ratio of the signal-to-noise was calculated and compared to the auditory impression for 58 subjects. The calculated results showed a positive correlation to the auditory impression, and it was suggested that this would be a useful method for the quantitative evaluation of hoarseness.
Toward the use of the inverse filter as a diagnostic aid
Authors: Deller J. R. , Anderson D. J.
Published: October 2005

A preliminary investigation using degraded synthetic vowel sounds has shown the digital inverse filter (IF) to have significant ability to relate quantitative information about aberrant laryngeal behavior manifested in the acoustic speech output. The information was contained in the positions of the IF polynomial zeros in the z plane and in the consistency of the root placements as the IF was computed repeatedly over consecutive 25.6 ms analysis segments of the utterance. The analysis resulted in a graphic display of the complex z-plane roots and a vector of pattern features extracted from that display for each of several experimental cases. The pattern of zeros could be used to empirically relate information about underlying perturbation processes. To supplement visual processing, the feature vectors from a large collection of pole plots were used by a clustering procedure to determine the resolution of cases in the feature space. Significant for clinical application is the fact that the technique readily discriminated patterns of simulations of the four acoustic hoarseness types suggested by Yanagihara [N. Yanagihara, J. Speech Hear. Res. 10, 531–541 (1967)].
Spectral characteristics of /s/ misarticulating children
Authors: Stephens I. , Daniloff R.
Published: October 2005

One vein of research involving /s/ misarticulating children has delineated three major subtypes of articulatory gestures: lateralizers, interdentalizers, and “others.” This last group appears to be highly heterogeneous and thus difficult to incorporate under a single label. Multiple /s/ productions of three lateralizing and three interdentalizing children as well as three normals were analyzed spectrographically. All samples were judged live to be clearly defective or clearly acceptable in the manner indicated. Based upon the spectral data, an attempt was made to define corresponding archetypes. [Work supported by NINCDS.]
Control of speech prosody in Broca's aphasia
Authors: Danly Martha , de Villiers Jill G. , Cooper William E.
Published: October 2005

A typical clinical description of the speech of Broca's aphasics includes the characteristics of nonfluency, agrammatism, and dysprosody. This study aims to objectively evaluate the subjective impression of dysprosody using computerized techniques to measure fundamental frequency (F0) and segmental timing. We examined three rudimentary aspects of normal speech production: (1) terminal falling F0 contour in utterance-final position, (2) declination of F0 peaks throughout the course of an utterance, and (3) segmental lengthening in utterance-final position. Seventy-five two-word utterances, extracted from the spontaneous speech of three Broca's aphasics, were found to exhibit both terminal falling F0 contours and declination despite interword pauses of up to 3.5 s. However, the timing of these utterances showed no utterance-final lengthening. These results are discussed in terms of the speech planning capabilities of these patients and the apparent dissociation between programming of F0 and timing. A controlled experiment was conducted in order to rule out the possibility that a phonetic influence masked utterance-final lengthening in the spontaneous speech sample; the results confirmed the previous observations for both segmental timing and F0. [Supported by NIH Grants NS 11408, NS 13028, and the MIT Research Laboratory of Electronics.]
Articulatory errors in mainstreamed hard-of-hearing and deaf children
Authors: Gold Toni
Published: October 2005

The purpose of this study was to compare the kinds of articulatory errors made by hard-of-hearing and deaf children integrated into regular public schools. Tape recordings were made of the children reading a set of test sentences. Phoneme scores were generated for each child based on the number of phonemes correctly produced. Results showed that although the deaf group produced significantly more phoneme errors than the hard-of-hearing group, the pattern of errors was very similar for both groups of children. That is, the relative frequency of different error types within each group was similar. These patterns were also quite similar to those previously obtained from children at schools for the deaf. Thus, to a first approximation, for the case of segmental errors, the primary difference between the two groups of children is that of frequency or error rather than differences in the pattern of phoneme errors. [Research supported by NINCDS.]
The effects of vowel height on fundamental-frequency control in the speech of profoundly deaf boys
Authors: Bush Marcia A.
Published: October 2005

The effects of vowel height on fundamental-frequency control were examined for eight profoundly deaf and five normal-hearing 9–13-year-old boys. Each speaker read a set of 40 phrases and 12 sentences containing from four to eight repetitions of the vowels /i, ɪ, ɛ, æ, a, ʌ, ɜ̀, ᴜ, u/ and the diphthong /ay/. Fundamental frequency was measured from computer-generated F0 contours near the center of each vowel token. On the average, cross-vowel variations in F0 were comparable for both deaf and hearing speakers, with fundamental frequency tending to increase with vowel height. The deaf speakers, however, appeared to fall into two groups: those for whom cross-vowel variations in F0 were relatively small, and those who produced the high vowels /i/, /ɪ/, and /u/ with excessively high F0. Differences between these two groups of deaf speakers have been examined relative to their articulatory proficiencies, and mechanisms responsible for the F0 variations within the latter group will be discussed. [Work supported by NIH.]
Multiple linear regression analysis of errors in deaf speech
Authors: Stromberg Harvey , Levitt Harry
Published: October 2005

A multiple linear regression analysis was performed relating percent intelligibility to segmental and suprasegmental errors in the speech of the deaf. Segmental errors were categorized in several ways according to intended phoneme, produced phoneme (or omission), location in work, and articulatory features involved. Suprasegmental errors were subdivided into 26 basic types within five broad categories (source characteristics, pitch, stress, timing, and rate). The analysis was repeated several times using different error groupings. Relatively small weightings were obtained for the majority of error types. The ranking of errors with respect to their effect on intelligibility was found to depend on how the errors were categorized. Both of these results are a consequence of the high multiple correlations between errors in the speech of the deaf. Nevertheless, a few error types were found to be relatively independent of other errors and these showed extremes in weighting, i.e., either having a marked or comparatively small correlation with reduction in intelligibility. [Work supported by NINCDS.]
Context-conditioned specification of vowel identity
Authors: Verbrugge Robert R. , Shankweiler Donald , Fowler Carol
Published: October 2005

Consonantal environment does not aid vowel identification universally, but preserves and sharpens the information for vowels differentially. In a vowel recognition task, listeners heard one of two test series: /pVp/ syllables or isolated vowels. The test items were spoken by a single male talker and contained a balanced distribution of the vowels /i, ɪ, ε, æ, a, ɔ, ʌ, ᴜ, u/. During each block of 90 test trials, listeners targeted for one of the nine vowel types, checking “Yes” when they recognized an instance and “No” otherwise. For both misses and false alarms, there was a strong interaction between vowel type (close versus open) and context type (/pVp/ vs /V/). The open vowel pairs (/ɛ/æ/ , /ʌ/a/) showed consistently superior recognition in the /pVp/ consonantal environment; others did not. Asymmetries in confusion errors were observed for several vowel pairs in both environments. A dynamic articulatory model of the syllable can provide a parsimonious account for these effects. Listeners may be sensitive to acoustic patterning that specifies vowels as dynamic gestures; vowel recognition will vary in precision depending on how the consonantal envirionment structures the dynamic information in sound. [Research supported by NIH grant HD-01994 to Haskins Laboratories.]
More on violin plate tap tones
Authors: Hutchins Carleen M. , Esly Mary Lee
Published: October 2005

Traditional violin making practice indicates that the “tap tone” or eigenmode 5 of the free top plate of a normal violin should come about F sharp. 370 Hz for good tone and playing qualities in the finished instrument. To check with earlier findings reported on eigenmode relationships in normal violas [Hutchins, J. Acoust. Soc. Am. 59, S34(A) (1976); Hutchins, “Another Piece of the Plate Tap Tone Puzzle,” Catgut Acoust. Soc. Newsletter No. 28, 22 (Nov. 1977)], six conventional violins have been made having mode 5 in both top and back free plates at 370 Hz (±3Hz)—also with mode 2 within 6 Hz of each other in the same pair of plates. Problems of achieving these mode relationships when graduating the two plates and resultant tone qualities will be discussed and the violins demonstrated.
Discovering guitar resonances using auditory techniques
Authors: Schultz W.
Published: October 2005

A nonelectronic method for estimating frequency and relative intensity of air and wood resonances in a guitar has been tested experimentally. Wood bars are struck with equal vigor first over the open air port, then over the closed port and loudness ratios estimated by listening to the fundamental. Those ratios furnish a measure of relative intensity of resonances excited by the acoustic energy injected into the body of the guitar by the bars. Loudness ratios plotted versus note (frequency) present a signature for a given guitar. if both plates are damped and a second curve is run, one is able to pick out the air and the wood resonances. Loudness ratios have been plotted for several guitars from E2 to C6. A comparison with data taken with sophisticated electronics equipment will be shown. It is hoped that this method will enable luthiers without electronic equipment in their shops to discover the resonance characteristics of a good guitar and eventually to improve on its musical characteristics.
Ab initio calculations of the oscillations of a clarinet
Authors: Schumacher R. T.
Published: October 2005

The internal oscillating functions volume velocity, pressure, and reed displacement have been calculated for a clarinet. The data used, all in the literature, are the mechanical properties of the reed, the geometrical measurements of the instrument, the properties of air, properties of tone holes [A. H. Benade, J. Acoust. Soc. Am. 41, 1609 (1967)], and data and calculations on the flow of air through a slit. From these, the input impedance Z(ω) is calculated, and is used to find an effective reflection function r(t). The latter is used in an algorithm [first used in calculating bowed string oscillations: M. E. McIntyre and J. Woodhouse, Acoustica 41 (in press)] that permits rapid numerical integration of the integral equations of motion of the system. The normal behavior of clarinets is observed in both chalumeau and clarion registers. Multiphonics are also calculated. Steady state behavior agrees qualitatively with the previous calculations [R. T. Schumacher, Acustica 40, 298 (1978)] to the extent that the latter are comparable with the present more elaborate model.
On reducing auditory feedback in hearing aids
Authors: White Richard E. C.
Published: October 2005

An inherent feature of a conventional magnetic earphone is that the diaphragm motion which generates acoustic output also gives rise to unbalanced displacing forces acting on the earphone's case. Although the displacements of the case are small, the resulting acoustic radiation may be sufficient to cause feed back, particularly with high gain hearing aids. Following a suggestion by Mead Killion, an experimental dynamically balanced earphone system was constructed. Two conventional miniature earphones were coupled back-to-back so that their diaphragms always moved in opposite directions, thus reducing the net out-of-balance force on their cases. The acoustic outputs of the earphones were delivered to the hearing aid tubing via a simple manifold. The success of the scheme was confirmed both by the reduced vibration amplitude of the coupled cases and by a lower level of radiated sound. Preliminary results suggest that in the absence of other limitations this system could allow hearing aid gain to be increased by about 10 dB before the onset of feedback. [Work supported by NINCDS.]
Contributions to N-2-4, N-3-4, N-4-4, θ-2-4, and θ-3-4 hemispheric sound reproduction technology
Authors: Bauer B. B.
Published: October 2005

The dimensions of the problem of sound pickup, recording, transmission, and reproduction over the 2-steradian space surrounding the listener usually is determined by the number of transmission channels economically available for recording and broadcasting—2 in the present-day home records and receivers but with the possibility for expansion to 3 or 4. The problem is complicated by the mandamus of stereo- and mono-compatibility and by the requirements of the artist/producer who seeks superior editing capabilities for creating an effective sonic performance unaided by the audio-visual effects and the psychological aid of a live performance. Some of the theories of surround-sound hemispheric recording and reproduction are outlined together with proposed implementations. A demonstration of 2-channel hemispheric sound reproduction will be provided in the display area.
Reflection of acoustic waves in a duct owing to discontinuous temperature gradient and cross section
Authors: Cole John E.
Published: October 2005

In the exhaust ducts of both internal combustion engines and heat exchangers, mean temperature changes cause the sound speed to vary in the direction of wave propagation. The equation that describes sound propagation in an ideal gas with an exponential variation in sound speed admits an exact solution in terms of known functions [J. E. Cole, III, “Sound Propagation in a Duct with Axial Sound Speed Variation: An Exact Solution,” J. Sound Vib. (in press)]. This general solution is used to evaluate the reflection and transmission coefficients for waves in a rigid duct with discontinuities in temperature gradient as well as, for the case of plane waves, in cross section. These results are shown to specialize to the standard results obtained for isothermal sound propagation. The limits of validity of the isothermal solutions are discussed and example calculations are presented.
Frequency spectra of solutions of stochastic equations, with applications to spectral broadening of waves propagating in a random medium
Authors: Wenzel Alan R.
Published: October 2005

Formulas for the cross-correlation and spectral density functions of the solution of a general linear time-dependent stochastic equation are derived. The analysis is based on a modification of the smoothing method. The formulas are applied to the case of radiation of scalar waves by a random point source in a three-dimensional random medium. The medium is assumed to be statistically homogeneous and isotropic and to be statistically independent of the source. An approximate expression for the power spectrum of the wave is obtained for the case in which the characteristic frequency of the source is much greater than that of the medium. This expression shows that the wave spectrum tends to a limiting form (the fully developed spectrum) with increasing propagation distance. It is also found that the total signal power is conserved as the spectrum evolves. Results obtained for the case of a narrow-band source show a progressive broadening of the wave spectrum with increasing propagation distance and/or with increasing strength of the randomness of the medium, in agreement with observations.
Measurement and analysis of the dynamics of mechanical structures
Authors: Richardson Mark
Published: October 2005

This paper discusses modern methods of testing, modeling, and analyzing the dynamics of mechanical structures. The topics covered are mathematical modeling of structural dynamics, modes of vibration, the normal mode versus the transfer function technique for structural testing, and identifying modal parameters from transfer function measurements. As indicated, much of the discussion concerns the modes of vibration of mechanical structures which turn out to be the link between the testing and analysis methods discussed in this paper. These methods are based upon the use of digital computers, and algorithms such as the finite element method for modeling and analysis, and digital filtering such as the fast Fourier transform for dynamic measurements. Some of the latest techniques for graphically displaying modes of vibration using low cost measurement instrumentation will also be presented.
Computer aided evaluation of viscoelastic properties using a reduced temperature format
Authors: O'Keefe E. J.
Published: October 2005

Accurate determination of viscoelastic properties is essential for the proper design of isolation mounts, damping layers, and resonant dampers. Polymeric materials typically used in these applications have complex stiffness moduli which are a function of temperature, frequency, and strain level; but these effects are not always accounted for when specifying material behavior. Simplifications in mathematical analysis and procedure using a resonant beam technique permits a more convenient specification of properties of samples tested in extension or shear configurations. Despite this test simplification, material specification would be unnecessarily confusing unless presented using a new format termed a reduced temperature plot [D. I. G. Jones, Shock and Vibration Bulletin, 1978]. The intent of this paper is to demonstrate how a computer oriented process can analyze test data, put the data into simplified format using reduced frequency analysis, and then use the information in the design of viscoelastic components.
The relative contribution of rise time, steady time, and overall duration of noise bursts to the affricate-fricative distinction in English: A reanalysis of old data
Authors: van Heuven Vincent J.
Published: October 2005

The results of an unpublished study by Gerstman (1957) indicate that variations of the rise time of a noise burst provide a more powerful cue to the English affricate-fricative distinction than similar variations in steady state duration of the noise burst. Since this finding is counter to the general sensitivity to such durational phenomena (indicating that the human ear is more sensitive to steady state duration differences), I propose a reanalysis of Gerstman's data. Since both rise time and steady time increments add to the overall duration, I have factored out this shared property. It then appears that overall duration explains about 75% of the response variance, whereas rise time or steady time by themselves only explain an additional 7%. I claim that my analysis is more realistic from a perceptual point of view. [Research supported by a grant from the Dutch Organization for the Advancement of Pure Research (Z.W.O.).]
The perception of sequences of identical and different stops in natural and synthetic speech
Authors: Raphael L. J. , Dorman M. F.
Published: October 2005

Previous studies using synthetic nonsense syllables have shown that listeners require a longer closure interval to report hearing a sequence of two identical stops (e.g., /ɛddɛ/) than a sequence of two different stops (e.g., /ɛbdɛ/). Acoustic measurements of real words in natural speech do not reveal an analogous difference in production. That is, speakers produce closure intervals in utterances such as paid Daley and paid Bailey that are essentially of the same duration. A series of experiments using natural speech is reported in which comparisons are made between the perception of (a) identical stop sequences in nonsense syllables versus real words, and (b) identical versus different stop sequences in real words. The results indicate that listeners do not require a greater closure duration to report hearing sequences of identical stops in either real words or nonsense syllables. This suggests that natural speech contains cues, not included in the synthetic syllables previously used, which inform the listener that two identical stops are intended. [Work supported by NICHD.]
Stop consonant perception: A comparison of several perceptual theories
Authors: Klatt Dennis
Published: October 2005

Acoustic cues to the identity of a plosive differ depending on aspects of phonetic environment such as features of a following vowel or consonant, properties of the previous segment, and stress. A complete perceptual theory should not only describe the perceptual strategy of an adult when confronted with this variability (and variability seen across talkers, transmission mediums, and speaking rates), but also account for the acquisition of these skills. In this paper we review the relative merits of burst invariance theories, relational invariance theories, the motor theory, analysis by synthesis, the locus theory, a theory based on the equivalent second formant F2′, and two new models called SCRIBER and LAFS [D. H. Klatt, J. Phonetics 7, (2) (1979)]. The advantage of SCRIBER and LAFS is that they can account for the differential use of various cues in different phonetic contexts by a conceptually simple decoding network structure. In its simplest form, the network represents all possible phonetic transitions of a language by distinct sequences of spectra. Perceptual abstractions such as [p]-ness or labialness are learned through association with the phonemic representations for words that are developed for speech production purposes (with the aid of a certain amount of natural acoustic similarity that exists for different realizations of a stop or of a distinctive feature). [Supported by NINCDS.]
The use of context in spectrogram reading
Authors: Zue V. W. , Cole R. A.
Published: October 2005

In order to assess the role of syntactic, semantic, and discourse knowledge in spectrogram reading, three short stories were recorded and speech spectrograms were made of the individual sentences of each story. The stories were presented one spectrogram at a time to an expert spectrogram reader who is instructed to read each story word-by-word without writing down segment labels. The three stories contained a total of 670 words, and 612 (91%) were correctly identified. The median reading time per sentence across the three stories was about 40 s, or about 20 times real time. However, syllable-by-syllable analysis of reading times in one story reveal that this value was inflated by a small subset of syllables and words that took a long time to decode—sometimes over a minute. The modal (most frequent) reading time per syllable fell between 1–2 s, or between 3 and 6 times real-time. Further analysis reveal that many common syllables were immediately recognized as complete patterns (e.g., “ment”, “tion”), and the use of context to recognize words from partial information was evident in many cases. Implications of the results for real-time spectrogram reading will be discussed.
Phase cancellation of auditory nerve fiber responses to combination tones, f2–f1
Authors: Moffat Anne J. M. , Capranica Robert R.
Published: October 2005

Low-frequency sensitive fibers from the amphibian papilla of anurans (Bufo americanus and Rana pipiens) respond to combination tones of the form f2–f1 in the same way as do mammalian cochlear nerve fibers, even though the structure of the receptor organs is quite different in the two classes. In anurans the shapes of the combination tone and pure tone tuning curves are similar, suggesting that the amphibian papilla fibers are responding to energy generated at the difference frequency. Furthermore, the response of a fiber to a tone pair, whose frequencies are harmonically related and whose fundamental is near the fiber's best excitatory frequency, can be almost totally eliminated by the addition of energy at the fundamental provided it is of appropriate intensity and relative phase. Systematically varying the phase of the fundamental produces a sharp minimum in firing rate with a maximum occurring about 180° later. These results suggest that a basilar membrane is not necessary for propagation of energy at the difference frequency; it can be transmitted by the inner ear fluids and the tectorial membrane. [Supported by NIH Grant NS-09244.]
Cat cochlear nerve fiber spike discharges: Interspike-interval-dependent spike delay
Authors: Gaumond R. P. , Molnar C. E. , Kim D. O.
Published: October 2005

Spike discharges of single cochlear nerve fibers in response to low-frequency (400–4000 Hz) continuous single tones were studied in two ways: (1) the occurrence-times of spikes were measured by conventional threshold-crossing techniques, and (2) the spike waveforms were recorded and analyzed. The occurence-time data yielded estimates of the instantaneous rate of discharge, conditional upon a value of stimulus phase θ and time-since-last-spike τ*. For a given fiber and stimulus, plots of rate versus θ for τ > 4 ms were generally independent of τ except for a τ-dependent scale constant; in addition, an apparent τ-dependent delay was seen as phase shift in the rate-versus-θ plots for τ < 4 ms. More complex behavior was occasionally observed for τ < 1.3 ms. The waveform of the second spike of a pair separated by a short interspike interval appears reduced in amplitude and contaminated by the waveform of the first spike, but the effect of these waveform changes on threshold-crossing time is sufficient to account for only a small fraction of the observed τ-dependent delay. It therefore appears that there is a τ-dependent delay of physiological origin, possibly associated with spike generation or propagation along the nerve fiber. [Supported by NIH grants NS07498, GMC1827, RR00396, NS00162.]
A nonlinear mechanical model of the peripheral auditory system: interpretation of neurally and acoustically observed distortion products (2f1-f2) and (f2-f1)
Authors: Matthews J. W. , Cox J. R. , Kim D. O. , Molnar C. E.
Published: October 2005

The model postulates linear dynamics of the middle ear, linear two-dimensional hydrodynamics of the cochlear fluid [Spenner and Cox, J. Acoust. Soc. Am. 62, S12(A) (1977)], and nonlinear dynamics of the basilar membrane relating transmembrane pressure to basilar-membrane motion. The model is solved digitally in the time domain in order to interpret two experimentally observed nonlinear phenomena: (1) propagating distortion products in the spatial distributions of the responses of populations of single cochlear nerve fibers [Kim et al., Scand. Audiol., (in press)], and (2) recent observations of distortion products in acoustic signals in the ear canal [Kemp, Arch. Otorhinolaryngol. (NY) (in press) and Kim (in preparation)]. Preliminary resulting from this model, as well as previous modeling results [Hall, J. Acoust. Soc. 56, 1818–1828 (1974)], show qualitative agreement with observations of the first phenomenon. [Supported by NIH grants: NS07498; RR00396; NS00162.]
Spatial coding mechanisms in neurons of the torus semicircularis of leopard frogs (Rana pipiens)
Authors: Feng Albert S. , Wallin Paul K.
Published: October 2005

The effect of horizontal position of sound on single unit responses in the torus semicircularis of leopard frogs (Rana pipiens) was observed using a movable sound source in free field. Two classes of neurons were noted on the basis of their response properties. One class of neurons responded (or showed suppressive responses) selectively to sound coming from about the midline. The other class of neurons changed their responses systematically as the sound source was rotated from one side to another. Most of these neurons in the second class showed greater firing rate when the sound was coming from the contralateral field and the firing rate reduced gradually as the sound was moved to the ipsilateral field. Additionally, a few neurons (class II) showed a marked shift in response latency, with or without alteration in the firing rate, as the sound source was moved in the horizontal plane. The existence of these two classes of neurons suggests that both the place and the population mechanisms are potentially useful for the frog to locate a sound source. [This study is supported by a grant from the Research Board of the University of Illinois and a Biochemical Research support grant awarded to A.S.F.]
Preservation of temporal information in the medial geniculate body
Authors: de Ribaupierre F. , Rouiller E. , de Ribaupierre Y.
Published: October 2005

Persistance in the medial geniculate body (MGB) of spike discharges synchronized with the phase of low frequency tones was investigated in cats anaesthetized with nitrous oxide. Only one out of ten single units responded to tone in a sustained manner. Eighty-eight of these units were analysed with high resolution interval and period histograms. Phase-locked activity was observed up to 1000 Hz, and 20% of the units showing “through” responses below that frequency were phase-locked. In the MGB, phase-locked units have a lower index of synchronization than in the periphery, indicating a higher degree of synaptic jitter at this level. For a given unit, the phase angle shifts linearly with frequency. The slope of these phase-versus-frequency lines is a precise measure of the total transmission delay from the cochlea to the MGB. This delay is a function of the characteristic frequency of the unit, showing that the time spread introduced by the cochlea between high- and low-frequency components of a signal is preserved up to the MGB. [Work supported by the SNSF grant 3.2000.073.]
Distribution of ABR (auditory brainstem response) components to monaural clicks in the guinea pigs
Authors: Özdamar Özcan
Published: October 2005

In response to clicks, five distinct, positive-going waves with short latencies are identified in guinea pigs. The different components of these auditory brainstem responses are affected significantly by the position of the electrodes. By using a monopolar recording scheme, ABRs are recorded with epidural electrodes in 18 electrode positions in the parietal bone of the guinea pigs. The results show that the first two components are largest on the ipsilateral side while the third and the fourth components are biggest on the contralateral side. Mapping the first four components on the guinea pig brain atlas suggests that the amplitudes are largest when the electrodes are closest to the suggested generators. Such experiments are expected to be helpful in identifying the ipsilateral and contralateral sources of the auditory brainstem responses.
Binaural interaction in human and cat brain stem evoked responses
Authors: Hosford H. L. , Fullerton B. C. , Levine R. A.
Published: October 2005

Early (less than 10 ms latency) auditory evoked responses were recorded between vertex and midline nape from humans and anesthetized cats. For both monaural and binaural clicks, averaged responses were obtained as a function of intensity. The averaged responses to stimulation of each ear were then summed and compared with the binaural response. For both humans and cats, the early portions of the binaural response (through the third positive peak) were nearly identical to those in the summed monaural responses. In contrast, the later waves of the binaural response differed significantly from those in the combined monaural responses. This difference, indicating binaural interaction, was usually found at all intensity levels for which the responses could be accurately measured. The similar behavior of these responses in both humans and cats suggests a possible correspondence of specific response components between these two species which may prove useful in providing an animal model for studying the origins of these potentials. [Work supported by NIH.]
Encoding of sound location by neurons in the auditory cortex of performing rhesus monkeys
Authors: Benson D. A. , Hienz R. D. , Goldstein M. H.
Published: October 2005

Single-unit activity was recorded from the auditory cortex of rhesus monkeys while they localized noise or tone bursts presented from five speakers positioned in a horizontal plane in front of them. One speaker was directly in front of the animal (0°) and two were on each side at azimuths of 37.5° and 75° from the midline. An index of sensitivity to sound location was defined for each unit as the ratio of the neural response rates between the most effective and least effective speaker locations. Out of 196 units, 122 having an index of 2.0 or greater were classified as location-sensitive units. Among the 122 units, 71 (58%) had their highest rate of response for the most contralateral speaker, nine (7%) for the most ipsilateral speaker, and ten (8%) for the center speaker. The most common observation was that response rates gradually decreased as the sound location was shifted from the most contralateral to the most ipsilateral speaker. Only three of the 196 units responded to one speaker location exclusively. [Research supported by NSF.]
Broadband measurements of volume scattering strength in the Mediterranean Sea
Authors: Doutt James A.
Published: October 2005

Broadband measurements of volume scattering strength between the surface and 1200-m depth within a frequency range of 1.6–16 kHz have been made in the major basins of the Mediterranean. If contours of scattering strength are plotted versus depth and frequency, four zones of high scattering strength can be identified which are generally present in all the basins. Changes in the location of these zones during the diurnal migration will be discussed and seasonal changes will be related to the biology of the scatterers. [Work performed at NATO SACLANT ASW Research Centre.]
Volume-backscattering spectra in the North Atlantic Ocean
Authors: Vent R. J. , Davies I. E.
Published: October 2005

Measures of acoutic volume-backscattering spectra using explosive sources were made in the eastern North Atlantic and southern Norwegian Sea (southwest and northeast of the Faeroe Islands) during August 1978. The experimental data were analyzed from 300 to 20 000 Hz with a resolution of 40 Hz. Spectra from both areas are noticeably different, particularly below 10 kHz where most volume scattering is caused by fishes possessing gas-filled swimbladders. Daytime spectra in the Norwegian Sea were dominated by a strong low-frequency peak between 1500–2000 Hz; concomitant high-resolution depth recordings indicated large concentrations of discrete targets layered between 100–350 m. The blue whiting, Micromesistius poutassou, is known to inhabit the entire area in commercial quantities during this time of year at these depths and is of the proper length (i.e., bladder size) to cause this strong peak. Daytime spectra of the southerly area exhibit features comparable with those commonly observed at midlatitudes which is attributed to swim-bladder resonance of smaller, mesopelagic fishes commonly associated with deep scattering layers.
Acoustic response of bubbly wakes
Authors: Holzmann J. M. , Reischman M. M.
Published: October 2005

The acoustic response of a bubble-laden wake can be predicted theoretically from knowledge of the bubble content. The inverse—surmising the bubble content from the acoustic response—can be accomplished also, albeit crudely. Studies indicate that the size of the bubbles formed by gas ejection from an orifice into a flow, depends on the ratio of the gas flow velocity to the water flow velocity [E. Silberman, 5th Midwestern Conference on Fluid Mechanics, (1957), and N. Hughes et al., unpublished data, NOSC (1978)]. The variation of the acoustic response of a bubbly wake exhausted from a moving vehicle was studied as a function of the rate of flow of gas and as a function of time (an indication of the rate of rise and dissolution of the bubbles). Full scale sea tests were conducted by echo-ranging on the gaseous wake at frequencies between 20–80 kHz. Results indicate that the acoustic response of the wake is a function of the amount of gas contained therein and the wake age. [Work sponsored by NAVSEA 033.]