bluuebunny/crossref_metadata_2025 huggingface dataset:
Speech synthesis by interpolation of prestored filter parameters
Authors: Gillmann R. A. , Ritea H. B.
Published: October 2005

A series of experiments as performed to compare the relative subjective quality of synthetic speech produced by several different sets of prestored filter parameters. These include (1) linear prediction coefficients, (2) reflection coefficients (k parameters), and (3) vocal-tract area functions. For each experiment, a set of filter coefficients for both phoneme nuclei and transitions were extracted from prestored and preprocessed digitized speech. Continuous sets of filter coefficients were generated by interpolation. Both linear and higher-order interpolation schemes were tested. Synthetic speech was also generated using only phoneme nuclei, in order to quantify the contribution of the transitional segments to overall speech quality. The various synthesis methods were subjectively evaluated by a panel of listeners. The results of this evaluation, along with sample recordings, will be presented.
Contribution of natural durations to speech synthesized by rule
Authors: Ingemann Frances
Published: October 2005

Rules for speech synthesis using the FOVE program at Haskins Laboratories incorporate some durational rules which attempt to produce differences in durations similar to those in natural speech. A recent set of rules produce speech in which the words are approximately 85% intelligible in relatively difficult sentences. To determine whether further attention to durational values would prove profitable in revising the rules, an experiment was conducted in which synthetic sentences by rule were modified by changing only the durations to match those of a reading of the same sentences by a human speaker. Frequencies and amplitudes of the speech by rule were unchanged. Listeners' performance on ten nonsense sentences of the type “The (adjective) (noun) (verb) and (noun)” improved from 77% to 85% word intelligibility when natural durations were used. It seems clear that further refinement of the rules for duration as well as for frequency cues is necessary. [Work supported by Veterans Administration contract V101 (134) p-342.]
New source model for narrow-band vocoders
Authors: Viswanathan R. , Makhoul J. , Huggins A. W. F.
Published: October 2005

Present-day narrow-band vocoders employ an idealized source (or excitation) model, which is either a sequence of quasiperiodic pulses for voiced sounds, or white noise for unvoiced sounds. This model seems to be largely responsible for the “buzziness” and lack of naturalness perceived in the resulting synthesized speech. We propose a new source model, which combines both pulse and noise sources in a novel way. Based on the observation that spectra of voiced speech sounds (e.g., voiced fricatives and even certain vowels) exhibit devoiced or incoherent high-frequency bands, the model divides the spectrum into a low-frequency region and a high-frequency region, with the pulse source exciting the low region and the noise source exciting the high region. The cutoff frequency that separates the two regions is adaptively varied in accordance with the changing speech signal. We present the advantages of the proposed model over the pulse/noise model, and describe a method for implementing it. Synthesis experiments conducted using the above model with manually extracted cutoff frequency data indicate the power of the model in almost entirely eliminating the “buzzy” quality. [Work sponsored by ARPA-IPTO.]
Testing recognition of computer-generated speech with elementary school children
Authors: Laddaga Robert , Sanders W.
Published: October 2005

Recently, two experiments were performed on recognition of computer-generated speech. One experiment tested recognition of letter sounds by first graders, the other tested fifth graders' recognition of consonant sounds in monosyllabic words. The systems tested were the Allen/Klatt system [J. Allen, 1977 IEEE Int. Conf. ASSP, p. 579 (1977)] the Votrax VS6 and ML1 systems (all phoneme synthesizers), and the institute's MISS system (linear predictive compression of recorded speech) [Sanders and Laddaga, J. Acoust. Soc. Am. 60, Suppl. 1, S76(A) (1976)]. Human speech was used as a control. A sign test was used to rank the systems; in both experiments the ordering was human speech, MISS, Allen/Klatt, Votrax. The pairwise comparisons were significant at less than the 1% level, except for three cases involving the control, MISS, and Allen/Klatt. A learning study was done for the letter experiment using linear probability models, whose results corroborated the ranking determined from the sign test. Study was made of individual problem sounds for each system in terms of human vocal parameters. [Supported by NSF grant SED74-15016-A02.]
Relative difficulty and robustness of speech recognition tasks that use grammatical constraints
Authors: Sondhi M. M. , Levinson S. E.
Published: October 2005

The well-known information theoretic property, relative redundancy, is a natural measure of grammatical constraint in speech. Low redundancy implies weak grammatical constraint which makes speech recognition more error prone and thus more difficult. High redundancy corresponds to strict grammatical constraints which reduce the difficulty and thus increase recognition robustness. We have derived methods for the exact computation of the relative redundancy of finite subsets of English and have applied our methods to eight speech recognition task languages that have appeared in the literature. A comparison of the difficulty of these tasks is made based on our results.
Suppression of transmission errors in DPCM coded speech
Authors: Steele R. , Goodman D. J. , McGonegal C. A.
Published: October 2005

We describe a technique for suppressing the effects of transmission errors in speech communication by first-order differential PCM. The technique is employed only at the decoder and thus requires no error-detecting or error-correcting coding. A simple algorithm based on the statistics of differences between adjacent received speech samples is used to identify erroneous transmissions. Error correction is achieved by means of an interpolative method. Signal-to-noise ratio measurements and listening experience demonstrate that the system significantly reduces the effects of transmission errors occurring at rates as high as 0.5%–5%.
On creating reference templates for speaker-independent recognition of words
Authors: Rabiner Laurence R.
Published: October 2005

The three aspects of a statistical approach to a pattern recognition problem are the selection of features, choice of a measure of similarity, and a method for creating the reference templates (patterns) used in the statistical tests. In this talk, we concentrate on methods for creating the reference templates. In particular, a method of combining word patterns from a number of speakers is proposed. The creation of templates, based on this method, is discussed. To test the ideas proposed here, a 54-word vocabulary word recognition system was implemented. Using a selected set of the training words to create the template, recognition accuracies of 85% were obtained in a forced-choice recognition test on the 54-word vocabulary using eight new speakers. The correct word was within the top five choices 98% of the time. Using a strategy in which all the training words were used to create the templates, the recognition accuracy fell to 77% and the correct word was within the top five choices only 89% of the time.
Interfrequency correlation of specularly scattered underwater sound
Authors: Shields R. B. , Medwin H.
Published: October 2005

The wind-driven surface of a large anechoic tank was used to study the interfrequency correlation between the amplitude fluctuations of 32 specularly scattered harmonic frequency components from 5 to 160 kHz. The temporal variations of the scattered pressure show maxima and minima that depend on the sound frequency. We find that the interfrequency correlation of pressure-amplitude fluctuations calculated over several “ocean” periods exhibits peaks and troughs. The negative correlations observed suggest the possibility of improving underwater communication during short-term signal fades by varying the carrier frequency to utilize the surface effect. [Work supported by ONR.]
Comparison of volume scattering prediction models
Authors: Brooks A. L. , Brown C. L.
Published: October 2005

Vertical profiles of scattering strength were successfully predicted on a seasonal basis for an ocean area off Bermuda from net trawl data on the vertical population density of 55 species of air-bladdered, midwater fish. The final predicted profiles compare favorably in shape and magnitude with measured profiles of scattering strength at 3.85, 5.0, 7.0, 9.0, and 15.5 kHz. At 3.85 kHz only one of the predicted scattering strength values lies outside of plus or minus one standard deviation from the measured value. For the predictions at 15.5 kHz, most values lie within 2 dB of the measured data. The surprisingly simple prediction model using fish abundance as a function of depth correlated with measured profile data, achieves a notably superior attainment in its predictive capabilities over an earlier, more complicated model which required inputs on difficult to obtain swim-bladder volume information. The success of the final prediction model is attributed largely to the fact that the vertical distribution density of the 55 species used serves as a reliable index to the total population of potential scatters within the insonified volume measured. Failure of the earlier model, based essentially on swim-bladder volumes was caused primarily by the inability of sampling methods to furnish sufficiently precise input information. [Work supported by NAVSEA.]
Extension of the theory of the disk parametric array
Authors: Bartram J. F.
Published: October 2005

In an earlier paper [J. C. Lockwood, J. Acoust. Soc. Am. 56, 1293–1294 (1974)], Lockwood analyzed a parametric acoustic array, the primary field of which is a thin disk of cylindrically spreading waves. This primary wavefield is perfectly collimated in one coordinate direction and omnidirectional in another, thus is a first step in a treatment of the fan beam. He assumes that finite-amplitude attenuation is not significant. The present paper extends Lockwood's analysis to the case of a sector of the disk; that is where the primary wavefield is no longer omnidirectional in one coordinate direction, but has a beamwidth less than 2π. Also, a taper function appropriate to cylindrical spreading is introduced to account for significant finite-amplitude attenuation.
Flight effects on predicted fan flyby noise
Authors: Heidmann M. F. , Clark B. J.
Published: October 2005

A paper study was made of the impact on PNLT (Perceived Noise Level, Tone corrected) and flyby EPNL (Effective Perceived Noise Level) when forward motion reduces the noise generated by the bypass fan of an aircraft engine. Blade passage frequency (BPF) of a typical subsonic tip-speed fan with BPF tone cutoff design features was systematically varied from 0.5 to 8 kHz. Two cases of predicted flight effects on fan source noise were considered: (1) reduced BPF tone level of 8 dB and (2) reduced broadband noise levels of about 2 dB in addition to reduced tone level. The fan source noise attained its maximum perceived noise reduction due to flight effects at a BPF of 4 kHz. The PNLT was reduced 7.6 and 10.0 dB for cases (1) and (2), respectively. The maximum reduction in 500-ft sideline flyby noise occurred at a BPF of 2.5 kHz. The EPNL was reduced 5.0 and 7.8 dB for cases (1) and (2), respectively. A factor of 2 change in tone frequency gave about one-half the maximum EPNL reduction.
Suprasegmentals in deaf speech: Preliminary results
Authors: Simon Claude , Gold Toni , Levitt Harry
Published: October 2005

Recordings of phrases and sentences, contrasting on the prosodic level, were obtained from normal-hearing and hearing-impaired children, 9–12 years of age. Preliminary results from an acoustic analysis of F0, durational, and intensity patterns indicate that, on questions, the normal-hearing children make use of the typical rising F0 contour, although not always on the appropriate syllable. Also, the slope of the rising F0 contour is not as consistent as was found for English adults [Ashby, Proc. Eighth Int. Congr. Phonet. Sci. (1975)l. The hearing-impaired children exhibited some control over prosodic pattern features, but these were not systematically appropriate. In particular, they appeared to use idiosyncratic durational cues contrastively between question and statement. One hypothesis is that durational cues compensate for the inability to reproduce the cause (F0 rise) of a perceived consequential acoustic change (increased intensity). This does not necessarily signal “deviant” language behavior since normal-hearing children go through similar stages at earlier ages. [Research supported in part by PHS Grant No. 09252 from NINCDS.]
Interior noise in a propeller-driven aircraft with a cylindrical fuselage
Authors: Bhat R. B. , Mixson J. S.
Published: October 2005

Interior noise in a propeller-driven aircraft with a cylindrical fuselage is analyzed in this paper. The frequency range of interest is divided into a low-frequency range (0–500 Hz) and a high-frequency range (500–5000 Hz) and different noise transmission mechanisms are assumed in these two ranges. In the low-frequency range, since the interior noise is mainly due to the overall cylindrical modes, the fuselage is treated as a cylindrical shell with the properties of the stringers and ring frames smeared over its surface. In the higher-frequency range, the interior noise is mainly due to the individual panel modes of the fuselage and is treated as such in the analysis. Fuselages of different lengths (10–25 m) and different diameters (2–6 m) are analyzed.
Speech processing aid for persons with profound sensorineural hearing loss
Authors: Schreiner P. G.
Published: October 2005

A speech recoding aid has been developed to enhance speech discrimination by profoundly hearing-impaired listeners. A unified system design employing amplitude compression, linear bandwidth compression, and equalization has been used to transform speech so that it more nearly conforms to the restricted frequency and amplitude response characteristics of an impaired-hearing system. Time-domain frequency compression of the speech signal by a factor of 4 was accomplished utilizing an analog pitch detection technique to allow real-time pitch-synchronous processing during voiced speech. An initial speech discrimination experiment using the recoded speech was performed with normal-hearing subjects. At the end of a three-period test sequence, the average discrimination scores for vowel contrasts were 92% and for consonant contrasts 75%. [Work supported by NIH.]
Listener-assessed intelligibility of hearing-aid-processed speech
Authors: Punch Jerry L. , Howard Mary T.
Published: October 2005

The capacity of listeners to yield preferences for hearing aids that provide maximally intelligible speech was evaluated by the method of paired comparisons. Discourse, spoken by a male talker with General American dialect, was processed by five hearing aids under conditions of quiet and a background of multitalker babble. Hearing-aid-processed revised CID sentences, spoken by the same male talker and embedded in the same multitalker background, were used as stimuli in establishing criterion measures of intelligibility. All stimuli were tape recorded and delivered via nonaural earphone to 90 normal listeners. The relationship between listener assessments of intelligibility for discourse and objective measurements of sentence intelligibility was evaluated by correlation analysis. Clinical implications of the results will be discussed. Findings represent preliminary evidence that measures of listener-assessed intelligibility may offer a valid, reliable, and rapid means of evaluating behavioral performance under the wide variety of electroacoustic characteristics available in a master hearing aid. [Work supported by VA.]
Translating hearing aid for “deaf” patients with nearly normal ultra-audiometric hearing
Authors: Halperin Henry , Cullen John , Berlin Charles , Killion Mead
Published: October 2005

There have been many attempts at speech transposing for the deaf by bringing speech information into lower-frequency bands to make use of residual low-frequency hearing. Because of the unusual hearing loss configuration referred to in the previous paper, it was decided to try translation in the opposite direction (i.e., to the high-frequency residual hearing band). This presentation will describe the hearing aid, construction, present some speech recorded through the aid, and discuss some considerations taken to insure the aid did not jeopardize the patients' residual hearing. Patients' experiences with the aid (lowering of speech detection threshold, distinguishing tone glides, and increased awareness of the environment) will also be discussed.
Rapid versus rabid: A catalogue of acoustic features that may cue the distinction
Authors: Lisker L.
Published: October 2005

In American English, initial /bdg/ often lack the acoustic feature taken as the defining feature of voiced stops; intervocalically before unstressed vowel /ptk/ lack aspiration, without which initial stops are not labeled /ptk/. Initially, the two categories differ in the timing of vocal fold adduction and onset of fold vibration, and several acoustic cues, all tied to the VOT difference, have been studied. Medially there is also a difference in the management of the larynx, though it results in a phonetically simpler contrast, one of voicing with no accompanying aspiration difference. Acoustically, however, the list of features that play, or might plausibly play a role is quite large. The word pair rapid-rabid, for example, might be affected by the following: (1) presence/absence of low-frequency buzz during the closure interval, (2) duration of closure, (3) F1 offset frequency before closure, (4) F1 offset transition duration, (5) F1 onset frequency following closure, (6) F1 onset transition duration, (7) [æ] duration, (8) F1 “cut-back” before closure, (9) F1 cutback following closure, (10) VOT cutback before closure, (11) VOT delay after closure, (12) F0 contour before closure, (13) F0 contour after closure, (14) amplitude of [i] relative to [æ], (15) decay time of glottal signal preceding closure, (16) intensity of burst following closure. Even if some of these should turn out to be perceptually negligible, enough of them surely have cue value to make it a formidable task to justify preferring an acoustic to an articulatory account of the distinction between the two English words. [The support of the National Institute of Child Health and Human Development is gratefully acknowledged.]
Role of stop consonants in word recognition
Authors: Jakimik J. , Cole R. A.
Published: October 2005

The perceptibility of various phonetic features during word recognition was assessed by having listeners detect systematic mispronunciations of words in a short story. Mispronunciations were produced by changing a single-consonant segment to produce a nonsense word (e.g., “boy” to “poy”). The rationale behind the experiments was that, in order to perceive a word as mispronounced, the listener must make a phonetic discrimination. Therefore, the listening for mispronunciation task examines the use of phonetic information during the process of recognizing words from fluent speech. The results of six experiments revealed that changes involving prestressed word-initial-stop consonants were detected more often than changes involving any other consonant. Thus, voicing changes were better detected in stops than in fricatives (70% versus 38%). Changes in manner of articulation were also better detected in stops than in fricatives (84% versus 53%). Changes in place of articulation in stops were better detected than place changes in nasals (77% versus 64%) and voicing changes in stops were better detected than place changes in nasals (75% versus 69%). Voicing and place changes in stops were consistently well detected (at least 70%) over three speakers differing in speech style and rate. The results showed that phonetic features are more perceptible in stops than in other consonants in fluent speech. The results suggest that stop consonants in word-initial position provide the most important and reliable phonetic information about a word's identity in fluent speech. They therefore play a special role in the word recognition process.
Onset spectra and stop consonant recognition
Authors: Dorman M. F. , Raphael Lawrence J.
Published: October 2005

In a series of experiments, we presented listeners signals consisting of an onset spectrum appropriate for one place of articulation followed at silent intervals from 0 to 150 msec by transition cues appropriate for a different place of articulation. As Fisher-Jørgensen [Ann. Rep. Inst. Phonetics (1972)] has reported for a similar transposition experiment, the onset spectrum determines place identification in some vocalic environments but not others. When the onset spectrum does determine place judgments it “overrides” the place of articulation signaled by the transition cues over silent intervals of up to 60 msec. [Research supported by NICH HD-01994.]
Patterns of response to within-category acoustic variation in dichotically presented stimuli
Authors: Carney Edward , Speaks Charles
Published: October 2005

As in a previous experiment [Carney and Speaks, J. Acoust. Soc. Am. 59, S7(A) (1976)], two sets of tapes for dichotic listening were prepared from synthetic stop-vowel stimuli which varied on a voice onset time (VOT) continum. Each set contained the same three voiced syllables (ba, da, ga) in combination with one of two sets of voiceless syllables which differed in VOT by 30 msec from set I to set II. The two sets of voiceless syllables differed only in acoustic structure, not in subjects' identification. Six stimulus-onset asynchronies were used for each of eight subjects, and, in the present experiment, the syllables were aligned by onset of their consonantal portions. Analysis of errors revealed that subjects used V features to construct “blend” error responses significantly more often in set II (longer VOT) than in set I. Results are discussed with reference to “graded feature detectors” [Miller, Percept. Psychophys. 18, 389–397 (1975)] and an alternative “decision” model. [Work supported by USPHS Grant No. NS-12125.]
Acoustic memory effects for consonants with lengthened transitions
Authors: Mandler R. , Dechovits D.
Published: October 2005

Differences in acoustic memory effects between consonants and vowels have led to the assumption that transience of the acoustic signal may affect persistence in immediate memory [Crowder, J. Verb. Learn. Verb. Beh. 10, 587–596 (1971); Crowder, J. Exp. Psychol. 98, 14–24 (1973)]. The present study was undertaken to determine whether less transient consonants are more persistent than natural stop consonants. Stop stimuli with lengthened F2 and F3 transitions employed in a perceptual study reported on at the last meeting of this society were utilized. Data resulting from stimulus suffix and recency effect tests indicate that these stimuli give results characteristic of short-transitioned stops. Thus, transience is not a factor in acoustic storage.
Room reverberation effects on recognition of some consonant features
Authors: Gelfand S. A.
Published: October 2005

The effects of real room reverberation (T=0.75 sec) on speech sound recognition was investigated for young, normal-hearing subjects. Initial versus final and quiet versus reverberant results were significantly different. Place information was most affected, followed by frication. Stop and nasal information were next affected. Voicing was quite robust; and duration, sibilance, and liquid information were virtually unaffected. Several interesting confusion patterns emerged. Except for the relatively high susceptibility of frication, the effects of reverberation on speech recognition seem somewhat similar to that reported for masking and low-pass filtering. Reverberation appears to result in temporal smearing of the speech signal, so as to act as a speech-shaped masking noise. Also, short-duration events appear lengthened, and seem to be associated with stops being reported as fricatives; and relatively long temporal spreading of the fundamental and lower formants appears to be associated with stops being reported as nasals. Comparison of the results with previous data obtained with artificially induced reverberation revealed some qualitatively and quantitatively different effects.
Reduction of community noise levels through effective vehicle noise legislation
Authors: Lawrence Anita
Published: October 2005

Legislation limiting the noise emission of new and/or in-service vehicles has the obvious aim of reducing community annoyance caused by traffic noise, but the effectiveness of such legislation must be questioned. Firstly, the rank ordering of the noise levels emitted by different vehicles changes according to the particular vehicle operating mode specified for the test, yet most current legislation specifies only one operating mode which is itself of limited relevance to urban or highway traffic conditions. Secondly, there is still a wide discrepancy between the predicted lower traffic noise levels which should result from quieter vehicles and acceptable community noise levels. Thus, for the effective protection of a community against traffic noise, legislation should be extended to include at least the following: (a) the measurement of a vehicle's noise emission in several operating modes, (b) the restriction of vehicle movements with respect to routes and times, and (c) the provision of compensation to owners of adversely affected buildings so that the attenuation provided by their external envelopes may be improved.
Computational experiments on the effects of inlet turbulence and inflow distortion on fan noise
Authors: Groeneweg John F.
Published: October 2005

Existing solutions to the problem of sound production by an axial-flow fan interacting with inlet turbulence and inflow distortion (Marvin E. Goldstein et al., NASA TN D-7676, May 1974 and NASA TN D-7667, June 1974) were evaluated over a range of inflow parameters. Sound power in the fan fundamental and second harmonic tones was computed and the modal power distributions contributing to the total tone power were identified. Comparisons and contrasts between the relations of input parameters to sound power produced were made for the two forms of inflow disturbance. It was found that the bulk of the modal power was carried by modes near cutoff for both forms of inflow disturbance when described by parameter values typical of those expected in practical fan test situations. The implications of the numerical results for the design of passive inlet flow control devices proposed to simulate flight conditions during static fan tests are discussed.
Effectiveness of an inlet flow turbulence control device to simulate flight fan noise in an anechoic chamber
Authors: Woodward R. P. , Wazyniak J. A. , Shaw L. M. , MacKinnon M. J.
Published: October 2005

A hemispherical inlet flow control device was tested on a 50.8-cm (20-in.) diameter fan stage in the NASA-Lewis anechoic chamber. The control device used honeycomb and wire mesh to reduce turbulence intensities entering the fan. Farfield acoustic power level results showed about a 5-dB reduction in blade passing tone noise at 90% design fan speed with the inlet device in place. The device resulted in about a 10-dB reduction in multiple pure tone generation at this fan speed. Hot film cross probes were inserted in the inlet to obtain data for two components of the turbulence at 65% and 90% design fan speed. Without the flow control device the axial intensities were below 1.0% while the transverse intensities were almost twice this value. The inflow control device reduced the circumferential turbulence intensities by a factor of three and also reduced the axial length scale.
Empirical model for inverted-velocity-profile jet noise prediction
Authors: Stone James R.
Published: October 2005

An empirical model for predicting the noise from inverted velocity-profile coaxial or coannular jets is presented and compared with small-scale static and simulated-flight data. The model considers the combined contributions of as many as four uncorrelated constituent sources: the premerged-jet/ambient mixing region, the merged-jet/ambient mixing region, outer-stream shock/turbulence interaction, and inner-stream shock/turbulence interaction. The model for both mixing regions is developed from the NASA interim prediction method for jet noise. The noise from the merged region occurs at relatively low frequency and is modeled as the contribution of a circular jet at merged conditions (between inner and outer streams) and total exhaust area, with the high frequencies attenuated (since the high-frequency region of this fictitious jet does not exist). The noise from the premerged region occurs at higher frequency and is modeled as the contribution of an equivalent plug nozzle at outer stream conditions, with the low frequencies attenuated (since the outer jet is broken up rapidly, before much low frequency is generated). The shock noise for each supersonic stream is calculated from a modification of the Harper-Bourne and Fisher (1973) model.
Space-time correlations of airfoil noise
Authors: Miller W. R. , Bucha M. P. , Meeecham W. C.
Published: October 2005

Space-time correlation measurements of surface pressure fluctuations on airfoils, immersed in a cold air jet, with their farfield sound were made over the exit velocity range of 68–190 m/sec (Mach 0.2–0.6). Measurements of surface pressure fluctuations were taken both at the one-third chord and the trailing edge of a 1-in. chord airfoil. The position of the farfield microphone was varied throughout the hemispherical region downstream of the jet exit. Analysis of the cross-correlation and delay time measurements on a 1-in. chord airfoil indicate that the dominant source region for the radiated sound is near the trailing edge. However, for the probe microphone mounted 1 in. from the leading edge of a second, 3-in. chord airfoil, two correlation peaks were recorded. The first corresponds to direct radiation from the probe location, and the second is due to acoustic transmission upstream from the trailing edge. The normalized cross-correlation coefficients were in a ratio of 1:5, respectively. This indicates that the sound from midchord is down 14 dB from the trailing edge sound; theory would indicate even less midchord sound. [Work partially supported by NASA and the TRW Foundation.]
Acoustic wave propagation through a plate
Authors: Dreyer John F.
Published: October 2005

By using variations in the complex exponential approach a new equation for transmission through a plate is developed. Energy and single interface transmission relationships are met. The supporting equations give the amplitude of the forward and reflected pressure and velocity components at the two interfaces. The pressure amplitude of the reflection at the first interface of an immersed plate is found to vary through zero from positive to negative as the thickness wave number is decreased.
Transmission and reflection characteristics of single and multilayered viscoelastic plates
Authors: Madigosky W. , Fiorito R.
Published: October 2005

An acoustic transmission matrix program capable of computing transmission (T), reflection (R), and absorption (A) coefficients for a single or multiple layer system of elastic/viscoelastic plates immersed in a fluid for arbitrary angle of incidence and frequency has been developed by extending the formulation of Young for elastic layers. [J. Young, J. Acoust. Soc. Am. 59, 1500 (1976)] The program which utilizes elastic/ viscoelastic material properties is applied to several cases of interest. The single steel plate is studied parametrically for various loss factors; single-layer high-loss plates of neoprene and plexiglass and, finally, two-layered systems of low-loss/ high-loss materials (steel/neoprene, steel/plexiglass) are also examined. Transmission and reflection coefficients are interpreted in terms of propagation and material constants. Modal and half-wave resonances are discussed and used to interpret the behavior of T as a function of incidence angle and frequency thickness product. Comparison is made between theory and experiment.
Stress concentrations in conventional shaped metal and unidirectional composite compliant tubes
Authors: Brigham Gerald A.
Published: October 2005

The design of compliant tube gratings for acoustic decoupling in water requires considerable detailed modeling of tube elastodynamics, array acoustics, grating resonant frequency, resonant bandwidth, elastomer loading, and tube stresses induced by uncompensated hydrostatic loading. Since the stresses depend on the same tube parameters as the acoustic characteristics it becomes necessary to simultaneously consider all grating factors including weight, thickness, and cost. For obvious reasons, however, tube strength must be given top priority in any design, and fundamental to estimating strength is a knowledge of stress risers in uniformly loaded oval shells. For conventional shaped tubes, such as those used by NUSC, the maximum stress is compression on the inside at the center of the curved ring segment. For very thick curved ends the ordinary thin shallow shell model is inappropriate and should be replaced by a more precise model. This paper presents the theoretical and emperical highlights of a detailed stress analysis of compliant tubes, including the flexural stress at the tube ends as well as the ring stresses.
The effect of fluid viscosity on the vibrations of two concentric tubes
Authors: Yeh T. T. , Chen S. S.
Published: October 2005

This paper presents an analytical study of coupled vibrations of two coaxial tubes separated by a viscous fluid to provide some additional insights into the effect of fluid viscosity. The paper is a sequel to the authors' recent paper, “Dynamics of a cylindrical shell system coupled by viscous fluid” [J. Acoust. Soc. Am. 62, 262–270 (1977)]. First the fluid forces acting on the tubes associated with small tube displacements are obtained in closed form based on the linearized Navier Stokes equation. Then, free and forced vibrations of the coupled tube/fluid system are analyzed. Finally, numerical results are presented for several cases to illustrate the effect of various system parameters. Some important conclusions are as follows: (1) The sensitivity of fluid viscosity on the added mass is much smaller than that on the damping coefficient. (2) In most practical application, the effect of the fluid viscosity on the system natural frequencies and mode shape are negligibly small. However, fluid viscosity contributes significantly to the modal damping. (3) A geometrically reduced scale model always yields higher damping than the full-scale system and the potential flow solution always underestimates the system damping.
The acuity of phonotactic approach in the green treefrog Hyla cinerea
Authors: Rheinlaender J. , Capranica R. R. , Gerhardt H. C.
Published: October 2005

The phonotactic responses of 41 individual females were videotaped to determine their head orientation prior to each leap and the direction and distance of the leaps in approaching the sound source broadcasting conspecific mating calls. Each approach consists of a sequence of zig-zag hops which results in alternating stimulation of the right and left ears. This form of navigation is at times supplemented by scanning motions of the head. In 80% of all hops observed the deviation of the head and the subsequent jump from the sound axis falls within ±30°. At head angles less than ∼10° the subsequent jump is less well oriented than for greater angles. This means that a certain minimum of interaural difference is required for accurate sound localization. These behavioral results thus indicate the magnitude of binaural cues that must be processed by the treefrog's CNS. [Work supported by NIH and Heinrich-Hertz-Stiftung.]
Auditory corticotectal connections of cat
Authors: Andersen R. A. , Snyder R. , Merzenich M. M.
Published: October 2005

Microelectrode recording techniques and the anterograde transport of tritiated amino acids (TAA) were utilized to demonstrate the projections of AI, AII, and the anterior auditory field (AAF) to the inferior colliculus (IC). Microinjections of TAA into AI resulted in two restricted, labeled laminae in the central IC of both sides: one in the dorsomedial division of the central nucleus (ICC) and one in the pericentral nucleus (ICP). The location and orientation of the projection arrays, as a function of the best frequencies of the cortical injection sites, were consistent with best frequency-position data obtained in microelectrode mapping studies in the ICC. With injections in AII near the border of AI, very sparse, diffuse labeling in ICP and in the dorsal and medial aspect of IC was observed. No projection to IC was observed in four AAF cases. These results indicate that (1) of these three fields, AI has the greatest descending input to IC; (2) the projection from AI is topographic (cochleotopic); and (3) the projections to the dorsomedial division of ICC are laminar and the position and orientation of the the laminae are appropriate with their being continuous with the morphologically laminated ventral lateral division. [Supported by NIH grant NS-10414.]
Effects of stimulus frequency on adaptation in auditory nerve fibers
Authors: Abbas Paul J.
Published: October 2005

Several experimental methods of depressing the response of auditory nerve fibers to tonal stimuli (such as two-tone suppression or stimulation of the efferent bundle) has been shown to reduce the response to signal frequencies at or near fiber CF more than to frequencies greater or less than CF. In this study we have used an adapting tone presented before each test tone burst to reduce the fiber's response. We then observed the effects of changing test-tone frequency. Discharge rate in response to the test tone was measured as a function of stimulus level with and without the adapting tone present. The adapting tone was always at fiber CF and held at a fixed level. The difference in discharge rate between presentation with and without the adapting tone was then plotted as a function of stimulus level. This difference was approximately constant over a range of stimulus levels [as reported by R. L. Smith, J. Acoust. Soc. Am. 59, S16(A) (1975)]. The depression in discharge rate was found to be approximately constant across a wide range of stimulus frequencies both above and below fiber CF.
Physiological masking functions in normal and acoustically traumatized cats
Authors: Shepard N. T. , Abbas P. J.
Published: October 2005

In cats that have undergone acoustic traumatization, it has been observed that several characteristics in the shape of single auditory nerve fiber tuning curves correspond to histological changes in the hair cells of the cochlea [N. Y. S. Kiang, M. C. Liberman, and R. A. Levine, Ann. Otol. Rhinol. Laryngol. 85, 752–768 (1976)]. Dallos and Cheatham (J. Acoust. Soc. Am. 59, 591–597 (1976)] using the whole-nerve action potential as a response have demonstrated masking curves in normal animals similar in shape to single-fiber tuning curves. We have measured whole-nerve action potential tuning curves (AP tuning curve) in both normal and acoustically traumatized cats to investigate the sensitivity of such a measure in reflecting changes in single-fiber tuning curves. A tonal masker in a forward-masking paradigm was used to elicit the measured responses. AP tuning curves were generated at several signal frequencies in order to measure the physiological changes at different places along the cochlea. A preliminary review of the data indicate that the AP tuning curves in acoustically traumatized animals can show a broadening of the tip region relative to normals.
Environmental features governing signal design in bat sonar
Authors: Simmons J. A.
Published: October 2005

Echolocating bats (800 species) represent a wide range of types of practical sonar systems evolved to fit specific acoustic environments and varying target situations. Bats which pursue isolated targets use narrow-band, CF signals for searching and low-distortion, moderately broadband FM signals for target characterization. Bats pursuing prey in the general vicinity of obstacles use two- or three-harmonic broadband FM-plus-CF signals to detect and characterize targets. These bats always have an ear out for potential flight hazards. Some bats operating in dense clutter use multiple-harmonic, very broadband FM signals for target detection and characterization. Other bats use narrow-band, long-CF signals for Doppler resolution of targets in clutter and moderately broadband FM signals for target description. Some species are adaptable and can use several of these signal patterns. Elements of sonar signal design are illustrated with real-world weights attached to their significance in data on bat echolocation. In particular, attention is focused on use of multiple-harmonic waveforms in clutter and the coupling of different signals into compound transmissions for processing by compound receivers.
Temperature coupling in the vocal communication system of the treefrog, Hyla versicolor
Authors: Gerhardt H. Carl
Published: October 2005

The pulse-repetition rate (PR) of mating calls of male treefrogs is highly temperature dependent. Since females are attracted by mating calls over a range of at least 9°C, the question arises: Do vocalizations produced at different temperatures attract females equally well? Gravid females were given a choice between two synthetic calls with PR's typical of those produced by males at about 16°C (15/sec) and 24°C (24/sec), respectively. Eight females chose the call with a PR of 24/sec when their body temperatures were about 24°C; subsequently, six of the same females responded when their body temperatures were about 16°C; they chose the call with a PR of 15/sec. Four females initially tested at 16°C chose the 15/sec call; subsequently at 24°C, two chose the 24/sec call and one chose the 15/sec call. These results were obtained at a playback level of 75 dB SPL re 2 × 10−4 μ bar; at 85 dB, females chose the 15/sec call at 16°C but failed to discriminate at 24°C. Evolutionary and neurophysiological implications will be discussed. [Supported by NSF and NIH.]
Public annoyance with motorcycle noise
Authors: Walsh John B.
Published: October 2005

To better understand public annoyance with motorcycle noise. Suzuki Motor Company, Ltd., had a survey conducted to investigate public attitudes towards the annoying characteristics of motor vehicles in general, the public perception of the causes of annoying noise from motorcycles, and the public attitude concerning methods to reduce annoying motorcycle noise. Two samples were included in the survey—a nationwide sample and a California sample. The survey results are useful in understanding the public attitude toward motorcycle noise, and in developing appropriate strategies to reduce public annoyance with motorcycle noise.
Annoyance scales for simulated VTOL and CTOL overflights
Authors: Galanter Eugene , Popper R. D. , Perera T. B.
Published: October 2005

Annoyance of simulated VTOL and CTOL overflights was measured by magnitude estimation scaling. Forty subjects were presented individually with a series of overflight sounds consisting of a mix of aircraft. L-1011 arrivals and departures at each of three intensity levels were interleaved with Boeing-Vertol B-347 overflights with flight parameters adjusted to produce three subjectively varying levels of “blade slap.” Each of the “blade slap” variations was also presented at three intensity levels. In addition the L-1011 arrivals and departures were octave filtered (10 dB) at each of three center frequencies: 315, 800, and 1600 Hz. These six “treated” spectra were also presented at three intensity levels. An L-1011 arrival at 89 dbA was used as the standard called “100.” Each of the 33 stimuli was presented in a different random order to each subject for their judgments. Plotted against dBA helicopters were more annoying than arrivals which were more annoying than departures. Plotted against EPNdB arrivals and departures showed equivalent annoyance, whereas helicopters continued more annoying. Helicopters with varying “blade slap” showed differential annoyance against dbA but were conformed by EPNL. [Work supported by DOT-FAA and NASA.]
On the nondetectability of phase delay distortion in hearing aids
Authors: Voroba B. , Beex A. A.
Published: October 2005

Since the time of Ohm and Helmholtz, researchers have argued over the detectability and importance of phase shift effects. Rarely has this subject been explored with hearing impaired listeners or their prosthetics. An experiment was performed in which normal-hearing and hearing-impaired subjects were presented with the combination of high- and low-pass speech components. The high-pass frequencies were alternately time delayed, or nondelayed, with respect to the low-pass signals so as to simulate the phase characteristics of a hearing aid. All subjects uniformly reported no detectable difference between the various test conditions suggesting that present hearing-aid phase characteristics have little or no detrimental effect upon listener perceptions.
Relationship of tonal masking to speech intelligibility in noise for listeners with sensorineural hearing damage
Authors: Leshowitz B.
Published: October 2005

The present investigation sought to establish empirical evidence for the audiological observation that listeners with normal pure-tone thresholds below 2000 Hz and selective high-frequency sensorineural hearing loss often experience great difficulty perceiving speech in a noise background. For patients with either noise trauma or presbyacusis, masked-speech intelligibility thresholds (S/N) were about 10 dB higher than for normal observers. In an effort to provide a psycho-acoustical explanation for the speech communication deficit, pure-tone masking patterns were measured. Relative to the normal control group, listeners with high-frequency hearing loss showed as much as 30 dB more upward spread of masking, often in frequency regions of normal pure-tone threshold. The strong positive relationship between the masked-speech intelligibility threshold and the upward spread of masking suggests that it may be possible to predict the patient's speech perception handicap in noise from audiometric measurements of masked threshold. Implications of the present work for development of close-talking-microphone hearing aids will be discussed. [Work supported by an NIH Postdoctoral Fellowship awarded to the author at the Institute for Perception Research, Eindhoven, The Netherlands.]
Asymptotic temporary threshold shift
Authors: Barry John P. , Bilger Robert C.
Published: October 2005

Five men having normal pre-exposure audiograms were monaurally exposed in a diffuse sound field for 24 hours to octave-band noise centered at 500 or 2000 Hz at 90 or 80 dB SPL, respectively. Each subject's exposures were two weeks apart. The growth of threshold shift was measured 10 times, and recovery was followed for a course of three days post exposure by a fixed-frequency-Bekesy-tracking procedure. Functional asymptotic threshold shift (ATS) was achieved for either noise exposure within eight hours at all 11 audiometric test frequencies. The maximum ATS for either exposure was the upper cut-off frequency of the noise with significant spread to the first octave above the noise's center frequency. For each exposure, growth was linear in logarithmic space. For multiple exposures on one subject at each band, the relationship between asymptotic level and noise intensity appeared to be linear with a slope of 1.6. Group data demonstrated that recovery from a 16.7 dB asymptotic threshold shift at 707 Hz required 98 h and was biphasic. Recovery from an 11.3 dB ATS at 2828 Hz required 20 h. Recovery from either noise was linear in logarithmic space.