bluuebunny/crossref_metadata_2025 huggingface dataset:
Psychophysical factors of spatial impression
Authors: Bilsen Frans A. , Kruysse Herman W. , Raatgever Johan
Published: October 2005

Spatial impression (or spaciousness) is an important perceptual attribute in room acoustics, implying (1) the sensation of a listener in a concert hall of being enveloped by the sound field and (2) the perceived broadening of the sound source. A psychophysical experiment will be reported using dichotic presentation of (filtered) white noise, in which the influence on spatial impression was investigated of three signal variables, viz., the interaural correlation, the center frequency, and the relative bandwidth of the filtered versions of the noise. Eight untrained subjects participated in a scaling experiment: They were presented 4 times with 80 (4*5*4) experimental conditions; subjective criterion was the perceived width of the sound image. The raw ordinal data were analyzed by canonic correlation analysis (CANALS); on the resulting data, ANOVA was applied. The main outcome of the experiment is that the interaural correlation and the center frequency are independent and adequate predictors of spatial impression. This result and the results of other experiments will be interpreted in the context of existing binaural theories. [Work supported by the Netherlands Organization for the Advancement of Pure Research (ZWO).]
Effects of roving level on binaural detection and discrimination on and off midline
Authors: Koehnke J. , Colburn H. S.
Published: October 2005

NoSπ detection thresholds and interaural time and intensity jnd's were measured both with and without a 10-dB random rove applied to the overall level. The stimulus for discrimination and the masker for detection were a 1/3-oct noise band centered at 500 Hz; for detection, the target was a 500-Hz tone burst. Thresholds and jnd's were measured using an adaptive, four-interval, two-alternative forced-choice procedure for several interaural time and intensity reference conditions including differences of 0 and 24 dB and 0 and 600 μs. Results indicate no effect of roving level for the 0-dB, 0-μs reference condition for binaural detection or interaural discrimination. For NoSπ detection, there is no effect of roving level or reference condition on thresholds. For interaural time discrimination, jnd's are larger off midline and roving level variation has no consistent effect on performance. For interaural intensity discrimination, jnd's generally increase off midline and are usually larger when measured with roving level than without. [Work supported by NIH.]
Lateralization on the basis of interaural envelope delays: The effect of additional frequency components
Authors: Dye Raymond H. , Niemiec Andrew J.
Published: October 2005

A lateralization experiment was performed in which threshold interaural envelope delays were measured as a function of modulation frequency (fm = 25, 50, 100, 200, 300, 400, and 500 Hz) for three- and five-component complexes whose center frequency (fc) was either 2000 or 4000 Hz. A two-alternative forced-choice procedure was used in which the envelope lagged to the right ear during one interval and to the left interval during the other. The level of each component was 50 dB SPL, and the signal duration was 200 ms with 10-ms linear rise-decay times. Thresholds obtained with three- and five-component complexes were quite similar regardless of fm, a finding that seemed consistent with the notion that the envelope is extracted from components interacting within an auditory filter, with more distal components having no effect. Surprisingly, making the outermost sidebands (fc − 2fm and fc + 2fm) diotic was found to severely impare one's ability to utilize envelope delays even when the fm's were quite high. These findings place in doubt the contention that the binaural auditory system extracts envelopes by monitoring the outputs of narrow-band auditory channels. [Work supported by NINCDS and AFOSR.]
Interaural envelope correlation and the high-frequency MLD
Authors: Bernstein Leslie R.
Published: October 2005

Data from a number of investigations suggest that listeners are extremely sensitive to interaural temporal disparities in the envelopes of high-frequency, complex waveforms. In the present study, an attempt was made to assess whether this sensitivity could be the basis for MLDs obtained at high frequencies. An adaptive, two-alternative forced-choice task was used to estimate detection thresholds for a number of interaural configurations including NoSo, NoSm, and NoSπ at a center frequency of 3571 Hz. In addition, a sinusoidally amplitude-modulated 3571-Hz tone whose carrier was interaurally in phase but whose modulator was interaurally phase-reversed was employed as a signal. The bandwidth of the diotic masking noise ranged from 50 to 400 Hz. For all conditions, dichotic thresholds were accounted for quite well by assuming that, for each listener, detection occurs when the signal decreases the interaural correlation of the envelope of the noise to some threshold value. This finding as well as alternative explanations will be discussed in terms of modern models and theories of binaural hearing. [Research supported by Air Force Office of Scientific Research.]
Optimal use of noise control foams
Authors: Bolton J. Stuart
Published: October 2005

Polyurethane foam is used with increasing frequency in noise control applications owing to its ease of handling and manufacturability. Until recently it has not been possible to predict its acoustical behavior with the accuracy that is possible for fiberglass, thus discouraging the use of foam in critical applications. Now theoretical models governing one-dimensional wave propagation in noise control foams have become available that have been shown to be capable of reproducing normal incidence absorption and transmission measurements accurately. These theories have been used to predict the behavior of foam in several absorption and transmission applications. In confirmation of largely anecdotal evidence, it has been found that the acoustical behavior of foam is very sensitive to its method of application to backing surfaces and to the way surface coatings are applied. In addition, it has been possible to identify optimum treatment configurations. These studies will be summarized here. Progress towards full three-dimensional foam models will also be described. Such models are necessary to allow the prediction of oblique incidence sound transmission and absorption. Finally, theory and experiments related to a new use of foam as a vibration damping material will be reported.
Measurement of acoustic impedance of sound absorbing materials in a free field at low frequencies
Authors: Champoux Y. , Allard J. F.
Published: October 2005

The two-microphone technique allows the precise measurement of acoustic velocity and consequently the determination of acoustic intensity. Using this principle, a method has been proposed to measure, in a free field, the acoustic impedance of sound absorbing materials. Good results were obtained for frequencies ranging from 700 Hz to 4 kHz [J. F. Allard et al., J. Sound Vib. 114(2) (1987)]. Recently, it has been demonstrated theoretically [Y. Champoux and A.L'Espérance, J. Acoust. Soc. Am. Suppl. 1 80, S56 (1986)] that for low frequencies, even if the source is several meters from the sample, the spherical nature of the waves has to be taken into account. This paper presents experimental evidence that confirms that the modeling correctly describes the phenomena. Further several refinements to the experimental technique, allowing precise measurements for frequencies as low as 250 Hz, will be demonstrated.
The replacement of mineral wool in perforated ceilings by a laminated textile
Authors: Frommer Glenn H.
Published: October 2005

A layer of 0.2-mm textile laminated onto a perforated metal band has been developed to replace inlays of 12-mm 34-k/m3 mineral wool in DAMPA ceiling products. Sound absorption values for the textile are 15%–20% better at frequencies under 315 Hz, and generally higher at all other frequencies, NRC = 0.75. This exceptional property is achieved by optimizing the streaming resistance of the textile and its lamination. The ceiling units conform with the requirements of the British Building Regulations, 1976, for a class-0 surface and the ASTM requirements for smoke density. In contrast with other porous materials, vibrational tests show no evidence of fallout. The Danish Environmental Prize has been awarded for the development of these products.
Acoustic issues from a marine surveyor's viewpoint
Authors: Hull Wesley V.
Published: October 2005

The ships and instrumentation used in the National Ocean Service hydrographic and bathymetric surveying represent capital investment of several hundred million dollars and recurring annual costs of tens of millions. The efficiency in survey coverage, while maintaining required survey accuracy, is of utmost concern. Deficiencies in any of the several types of acoustic systems used in the surveys can and do contribute significantly to the loss of survey production. This paper describes briefly three types of survey missions, highlighting the acoustic systems used and the known or preceived acoustic phenomenological factors that contribute to lost production. These systems include dual frequency echosounders, multibeam swath sonar systems, and conventional side scan. The paper also discusses emerging technology, now under consideration, including both interferometric and multibeam side scan systems, again with emphasis on the critical acoustic phenomena. Finally, a new concept dubbed “the acoustic knife,” for which an experimental project is now contemplated, is discussed.
Scattering of sound from the rough seafloor
Authors: Stanton T. K.
Published: October 2005

The scattering of sound from the rough seafloor and resultant echo fluctuations are functions of seafloor geomorphology and sonar parameters such as beamwidth, frequency, and angle of incidence. The scattering is very difficult to describe analytically and quite often requires numerical and empirical techniques. Like most rough interfaces, the seafloor can be described by two classes of surfaces: (1) stochastic and (2) deterministic. For both types of surfaces, it is essential to model the roughness as being two-dimensional, i.e., not striated. Because of the randomness of the seafloor, the echo will fluctuate from ping to ping as the sonar moves over the floor. Patches or distinct geomorphological features will cause deviations in the statistical properties of the echoes. [Work supported by the ONR.]
Shallow seismoacoustic experiments using shear waves
Authors: Stoll R. D. , Bryan G. M. , Flood R. , Chayes D. , Manley P.
Published: October 2005

During the summer of 1986 a series of seismoacoustic experiments were carried out in shallow water off the New Jersey shore. The purpose of these experiments was to measure the geoacoustic properties of the ocean sediments that comprise the upper few hundred meters of the sediment column. Seismic sources and receivers were deployed at or very near the bottom in order to excite shear waves in the sediment and minimize the effects of interference from water-borne propagation. The experiments were performed at several sites where prior field work had established physical properties and a detailed profile of the sediments. By using conventional air guns deployed in an unconventional way, strong interface and diving shear waves were generated, and these data were inverted to obtain shear wave velocity as a function of depth. The inversion results were then compared with the predictions of a geoacoustic model that accounts for the effects of voids ratio, overburden pressure, and other physical parameters. The in situ measurements from experiments and the gradients predicted by the model were in good agreement, suggesting a strong dependence of velocity on overburden pressure near the water-sediment interface. [Work supported by ONR, Code 1125 OA].
Quantitative experimental verification of seabed shear modulus profile inversions using surface gravity (water) wave-induced seabed motions
Authors: Trevorrow Mark , Yamamoto Tokuo , Badiey Mohsen , Turgut Altan , Conner Craig
Published: October 2005

A previously developed theory enables seabed shear modulus profiles to be calculated through the combination of water wave-seabed interaction theories and geophysical inversion methods. A new instrumentation system, consisting of three orthogonally mounted accelerometers and a pressure sensor, has been developed to measure water wave-induced pressures and seabed motions. This new passive remote system provides a fast and convenient method to determine in situ sediment shear modulus with depth profiles, without disturbing the sediment or drilling. Experiments have been conducted in various sediments and water depths off the coast of New Jersey. Extensive experimental data reduction techniques are developed to deal with real ocean data. Actual experimental results are given, along with quantitative measures of uncertainty and resolution. Comparisons between the experimental shear modulus inversions, in situ sediment strength tests, and laboratory analysis of core samples show that this method can accurately predict shear modulus to depths of 50 m or more. [Work supported by ONR.]
Acoustic wave propagation through porous media with arbitrary pore-size distributions
Authors: Yamamoto Tokuo , Turgut Altan
Published: October 2005

In the Biot theory, the effect of frequency on the oscillatory viscous forces within a porous medium is treated by replacing the kinematic viscosity ν by an oscillatory viscosity νF. Here, F is a function of angular frequency ω, the kinematic viscosity ν, and the single pore size a. In this paper, a mathematical expression of F is presented for arbitrary distribution of pore sizes that can be used in the Biot theory without modification. It is shown that porous media with a given permeability and porosity may be represented by an infinite number of pore-size distributions. The dispersion and attenuation of acoustic waves through such porous media are independent of the pore-size distribution at the low- and high-frequency limits, while they are strongly dependent on the pore-size distribution in the intermediate frequency range. For porous media with φ-normal pore size distributions having a given value of permeability, the maximum specific attenuation decreases and the bandwith of dispersion increases with an increasing standard deviation of the pore-size distribution. Finally, the generalized Biot theory for arbitrary distribution of pore sizes is compared with the entire data of compressional wave attenuation through surficial marine sediments given by E. Hamilton. Comparison between his data and the predictions from this theory show good agreement. [Work supported by ONR.]
Effects of seabed properties on acoustic normal mode propagation in a stratified shallow ocean
Authors: Badiey Mohsen
Published: October 2005

The pressure field of a point source in a shallow stratified ocean over a nonhomogeneous anisotropic seabed is calculated using normal modes. The sediment is modeled using the Biot-Yamamoto theory of poro-elastic media. The influence of geoacoustic properties of sediments on low-frequency transmission loss is investigated. It is found that the variation of permeability has large influence on acoustic wave attenuation, whereas the elastic properties variation has lesser effect. Finally, the existing model is used in an attempt to extract the depth structure of permeability and porosity of the seabed. [Work supported by ONR.]
Dynamic behavior of sediment and water-sediment interface. Homogenized process application to porous saturated media
Authors: Avallet C.
Published: October 2005

An application of the homogenized process to the dynamic behavior of marine sediments is presented here. The medium is considered as a porous viscoelastic solid saturated by a viscous fluid. Under the assumption of periodicity for pore structure (microscopic scale), the homogenization technique leads to the macroscopic description. The set of equations so obtained is similar to the classical Biot's results. The homogenized model is somewhat easier to use: A generalized Darcy's law governs the motion of the pore fluid relative to the solid [Auriault et al., J. Acoust. Soc. Am. 77, 1641–1650 (1985)]. A reasonable assumption allows the computation of the frequency dependence of the permeability from its quasistatic value. Using the homogenized set of macroscopic equations, compressional and shear waves in porous media, surface waves at fluid-porous solid interface, and reflection properties of plane acoustic waves were calculated. Results are compared to those obtained by Biot's theory and to experiments. The aim of this work was to show the applicability of the model to unconsolidated sediments (high porosity silt and clay or sandy media). [Work supported by D.R.E.T.]
Measuring the sound power of a noise source and detecting pure tones with a single instrument combining true 1/3 octave band digital filters and an FFT analyzer
Authors: Bjor Ole-Herman , Ese Gustav
Published: October 2005

In the past, there has been a requirement for determination of both the sound power of sources and an investigation of the pure-tone content. This is especially true in the computer and business equipment industry. Measurement of the sound power normally calls for standard (ANSI) class III 1/3 octave band filters, while pure-tone determination requires narrow-band (FFT) measurements; hence, two separate instrument systems were required. This paper describes a new instrument for these determinations in which the true standardized 1/3 oct filters and the FFT are combined. The procedure for automatically identifying prominent discrete tones per ANSI S12.10 is discussed.
Evaluation of a hearing conservation program at a large industrial company
Authors: Clark William W. , Bohl Carl D. , Davidson Lisa S. , Melda Keith A.
Published: October 2005

The hearing conservation program (HCP) of a large industrial company was evaluated by comparing the audiometric data of two groups of workers from three geographically separate plants. Group 1 was selected from individuals employed in areas where the time-weighted average (TWA) sound level exceeded 90 dBA and group 2 from individuals with TWAs of less than 85 dBA. Differences between mean STS values for groups and plants were the main criteria used in making judgments on the HCP effectiveness. In addition, age, sex, years of service, and nonoccupational noise exposure were evaluated. A significant difference in mean STS was found between the two groups; however, the “nonoccupationally exposed” group had more STS than expected. The male-female distribution, previous hearing loss, and nonoccupational exposure were judged to be contributing factors in the differences that existed between plants and groups. [Work supported by Grant OH 02128 from NIOSH.]
Sound propagation and community noise exposure considerations for enroute noise of advanced turboprop aircraft
Authors: Weslet John , Sutherland Louis C.
Published: October 2005

The sensitivity of predicted ground noise levels for advanced turboprop aircraft to changes in atmospheric absorption losses is reviewed, and the resulting community noise environments evaluated in terms of possible criteria for acceptable levels. Atmospheric absorption coefficients at high altitudes are subject to possible errors of over ±70% due to the current uncertainty in atmospheric absorption prediction models at the very low humidities involved. However, the integrated absorption loss over the entire propagation path is nearly independent of the particular prediction model chosen. The humidity and temperature structure of the atmosphere is a more significant source of variation in the total atmospheric absorption loss. Based on a reference profile of humidity content versus altitude, and existing models for a standard atmosphere, estimates of enroute noise of advanced turboprop aircraft are made and compared with available data. The noise exposure on the ground is considered in terms of both the maximum sound level and sound exposure level for one overflight, and the day-night average sound level for various scenarios of daily operations. These estimates of the resulting community noise exposure are compared to possible criteria for acceptable levels for single and multiple aircraft flyovers. [This work was supported in part by the Federal Aviation Administration.]
A theoretical interpretation of a dosage-effect relationship for the prevalence of annoyance in a community
Authors: Fidell Sanford , Green David M. , Schultz Theodore
Published: October 2005

A dosage-effect relationship by Schultz [“Synthesis of social surveys on noise annoyance,” J. Acoust. Soc. Am. 64, 377–405 (1978)], that relates community noise exposure to the prevalence of annoyance, has become a widely used tool in assessing environmental noise effects. Because Schultz's relationship is applied to a broad range of exposure conditions, and because it is entirely empirical, its application to specific situations is frequently challenged. A simple mathematical model can account not only for the shape of the relationship synthesized by Schultz, but also for the differences between Schultz's relationship and that proposed by Kryter [“Community annoyance from aircraft and ground vehicle noise,” J. Acoust. Soc. Am. 72, 1222–1242 (1982)]. A single parameter, representing response bias, suffices for this purpose. [This work was sponsored by the U.S. Air Force Noise and Sonic Boom Impact Technology program under Contract F33615-86-C-0530.]
Effects of hearing protectors on head diffraction
Authors: Franks John R.
Published: October 2005

The diffraction by the head and pinna of sound incident upon the ear has been well documented. However, the modification of head diffraction patterns by the placement of hearing protectors in, or over, the ears has not been investigated. Polar sensitivity plots were obtained in an anechoic sound field from the right ear of the Knowles Electronics Mannequin for Acoustic Research (KEMAR). Test frequencies ranged from 100–10 000 Hz in steps of 1/3 octave. Plots were obtained in the horizontal plane for three conditions: (1) ear open; (2) ear occluded with a malleable foam-type ear plug; and (3) ear covered by a conventional ear muff. Polar data were converted to field-to-drum transfer functions for every 45° change in angle of signal incidence for each condition. The diffuse-field ear-open transfer functions will be compared to previously published functions for KEMAR. The effects of ear occlusion with muffs, caps, and plugs as seen by attenuation and canal resonance shift will be discussed.
A theoretical model of the annoyance of individual noise intrusions
Authors: Fidell Sanford , Green David M. , Pearsons Karl S.
Published: October 2005

Self-reports of noise-induced annoyance can be modeled as the product of a rational, decisionlike process in which people discriminate among annoying and nonannoying noise intrusions heard in the presence of a reference distribution of noise exposure. This view, developed under the sponsorship of the U.S. Air Force Noise and Sonic Boom Impact Technology program, can assign explicit roles to both acoustic and nonacoustic variables in a probabilistic decision-making process. The model, expressible in spreadsheet form, permits identification of two components of annoyance judgments: direct annoyance, based on sensitivity to the immediate characteristics of acoustic signals, and response bias. The model also provides insight into the extent to which acoustic variables may be considered to cause annoyance.
The coordination of glottal with oral articulations in Icelandic and Hindi
Authors: Kingston John
Published: October 2005

In most consonants produced with glottal abduction, the opening is largely or entirely contained within the accompanying oral articulation. Furthermore, the peak glottal opening occurs at a constant interval from the beginning of the oral articulation in unaspirated stops and voiceless fricatives and at a constant interval from the release in aspirated stops, indicating tight coordination with the oral articulation [A. Löfqvist and H. Yoshioka, “Interarticulator programming in obstruent production,” Phonetica 38, 21–34 (1981)]. Icelandic and Hindi possess stops in which the glottal opening takes place largely outside the oral closure; in Icelandic preaspirated stops, abduction precedes the closure and in Hindi breathy voiced stops, abduction follows the closure. Both languages also have (post) aspirated stops with which the stops of interest can be compared. This study examined whether external glottal articulations are also tightly coordinated with the oral articulation of the consonant. One female speaker of each language has been recorded so far, producing words containing the stops of interest at different rates and with stress either on the syllable containing the stop or not. If the oral and glottal articulations are coordinated with one another, then changes in their individual durations due to changes in rate or stress location should covary. The duration of both pre- and post-aspiration in Icelandic covaried with the duration of the adjacent vowel, and the duration of preaspiration also covaried with the following stop closure, but the duration of postaspiration did not covary with the preceding stop closure. In Hindi, the duration of both breathy voice and (post) aspiration coratied with the duration of the preceding stop closure but the duration of neither covaried with that of the following vowel. Both kinds of Hindi stops are like those observed in other languages, but the relative timing of glottal and oral articulations in the Icelandic stops is dearly different. In that language, the oral articulation with which the glottal articulation is coordinated is the vowel or the vowel and consonant combined.
Temporal effects of geminate consonants and consonant clusters
Authors: Dunn Margaret H.
Published: October 2005

Current phonological theory analyzes geminate consonants as sequences of adjacent timing slots that completely share features while closing one syllable and opening the next. This analysis predicts that the temporal organization of utterances with geminate consonants is parallel to that of utterances including heterosyllabic consonant clusters. This prediction was tested using Finnish and Italian, two languages with very different temporal organizations. Five Italian and four Finnish subjects read lists of nonsense words including bilabial geminates and both homorganic and heterorganic clusters. The hypothesized equivalence of geminates and clusters was tested by examining the amount of closed syllable vowel shortening exhibited in the two environments. The results did show that geminates patterned with dusters, with respect to preceding vowel duration in both languages, but closed syllable vowel shortening was exhibited only in the Italian. This result suggests that the syllable may be used as a unit of temporal organization in Italian, but some other units of temporal organization must be proposed for Finnish. [Work supported by NIH Grant NS-13617.]
Stop consonant voicing in Malay-English bilinguals
Authors: Yeni-Komshian Grace H. , Bhathal Inderjit K.
Published: October 2005

The productions of two groups of Malay-English bilinguals were investigated. The subjects, native speakers of Malay, were asked to read Malay and English words that differed in voicing of initial and final stop consonants. The four subjects in the Malaysia group resided in Malaysia and were not exposed to a predominantly English speaking environment, and the two subjects in the U.S. group resided in the U.S. for 5 years. Results on word initial stops are reported here. In Malay, voiced initial stops are characterized by voicing lead and voiceless stops by short voicing lag. Comparison of the two bilingual groups revealed that, although there were no significant differences in the voiced productions, there was a shift towards a more Englishlike production for the voiceless stops by the U.S. group. Analysis of the English words showed no differences in the production of the voiced stops; however, the U.S. group produced the voiceless stops with significantly longer VOT values than the Malaysia group. None of the subjects showed a shift in voicing characteristics as a function of language. These results suggest that native Malay productions in bilinguals, residing in the U.S., were altered in a direction that is characteristic of English.
Timing of contextual nasalization in two languages
Authors: Huffman Marie K.
Published: October 2005

Coarticulatory patterns in nasality in two West African languages—Akan and Efik—will be described. These languages make different phonological use of the feature (nasal). Nasality is determined from nasal and oral airflow as recorded with a Rothenburg split mask. The focus is on the timing of contextual nasalization; in particular, the coarticulatory effects of nasal consonants on adjacent vowels that are not contrastively (+ nasal). These effects are said to vary depending on the phonological use of nasality in a language. In Akan, there is an oral/nasal contrast on vowels, even in the environment of nasal consonants; thus contextual nasalization may be limited, so as to preserve the phonemic contrast. In Efik, there is no such contrast on vowels, so contextual nasalization of vowels may be more extensive, beginning earlier, and ending later, as has been reported elsewhere for English. Data for several speakers of each language will be discussed. [Work supported by NSF.]
Cross-linguistic articulatory models of vowels
Authors: Jackson Michel T. T.
Published: October 2005

The mathematical and phonetic foundations of a family of techniques for quantitatively analyzing articulator positions during speech production will be discussed in terms of a small number of modes that span the observed space of articulatory variation. Particular articulatory positions are represented as weighted combinations of the modes; various naturalness conditions that depend on having multispeaker data can be used to resolve mathematical indeterminacies in the choice of modes. Results using measurement of articulator positions from sagittal x rays of English, Icelandic, Spanish, and Akan vowels suggest that the basis needed for any one language is of relatively small dimensionality. Typically, only two or three modes suffice to generate the observed range of articulator positions. However, not all languages have the same modes of articulator positioning. Thus a cross-language modal analysis requires higher dimensionality, i.e., more modes. In conclusion, there are systematic differences between languages in the functional organization of a set of articulatory primes. These differences in functional organization lead to the observed cross-language differences in modal organization. [Work supported by NSF.]
Cross language study of the effects of voiced/voiceless consonants on the vowel voice source characteristics
Authors: Chasaide Ailbhe Ní , Gobl Christer
Published: October 2005

Source characteristics of a vowel may differ according to the voiced/ voiceless nature of adjacent consonants. The postvocalic consonant could be particularly crucial, as vocal fold abduction for a voiceless consonant may be initiated considerably before oral occulsion. Here, CV (:) C utterances (where C = voiced/voiceless labial stop or fricative) were analyzed for female and male speakers of Swedish, English, and French. Characteristics of the voice source were measured from inverse filtered data using the four-parameter LF model developed at the KTH. Airflow recordings with a Rothenberg mask allowed inferences regarding incomplete vocal fold closure during the vowel and at onset and offsets. Results indicate major effects of a following consonant; the later part of the vowel preceding a voiceless consonant shows a marked drop in excitation strength and a steeper spectral slope, as might be expected when the vocal folds are opening but vibrating. A spectral consequence of this abducting gesture is a widening of the F1 bandwidth and an upward shift in formant frequencies. These effects were much less in evidence in French than in Swedish and English. The preceding consonant had comparatively little effect; full excitation strength is achieved almost immediately.
Phase-lock of spontaneous oto-acoustic emissions to a cubic difference tone
Authors: van Dijk Pim , Wit Hero P.
Published: October 2005

If a single external tone is used to study phase-lock of a spontaneous oto-acoustic emission, it is difficult to separate this tone from the emission signal. Therefore, two tones with frequencies f1 and f2 and levels L1 and L2 were presented to ears having a spontaneous oto-acoustic emission. Here, f1 and f2 produced a 2f1 − f2 distortion product close to (< 50 Hz) the emission frequency f0. Frequency spectra and zero-crossing time trend recordings were obtained for various values of L1, L2,f1, and f2. When the L1 and L2 were sufficiently high, the emission was phase locked to the 2f1 − f2 tone generated in the ear. When L1 and L2 were small, the emission was sustained at f0. At intermediate levels, the emission is not constantly locked to 2f1 − f2, but occasionally jumps to f0. The behavior described above is identical to that of a self-sustained oscillator in the, presence of noise, driven by an external tone [R. L. Stratonovich, Topics in the Theory of Random Noise (Gordon and Breach, New York, 1963), Vol. II, Chap. 9]. [Work supported by Z. W. O.]
Effects of frequency separation of primary tones on the amplitude of acoustic distortion products
Authors: Harris Frances P. , Stagnet Barden B. , Martin Glen K. , Lonsbury-Martin Brenda L.
Published: October 2005

The effects of frequency separation of equilevel primary tones, f1 and f2, on the amplitude of distortion-product emissions (DPEs) at 2f1 − f2 was investigated in 10 ears of five humans with normal hearing. The DPEs at 1, 2.5, and 4 kHz in response to primaries at 65, 75, and 85 dB SPL were generated with f2/f1 ratios varying in 0.02 steps from 1.01 to either 1.41 (4 kHz), 1.59 (2.5 kHz), or 1.79 (1 kHz). Results indicated that, in generating the maximum DPE amplitude, f2 − f1 frequency separation was systematically related to stimulus frequency and level. Thus, for all levels of stimulation, f2/f1 ratio was inversely related to DPE frequency so that higher ratios were most effective in generating DPEs at 1 kHz, while lower ratios elicited large emissions at 2.5 and 4 kHz. In addition, for all three DPEs, in obtaining maximum responses, primary-tone level was directly related to f2/f1 ratio in that lower ratios were most efficacious in generating DPEs to 65-dB stimuli, while higher ratios elicited larger DPEs in response to 75- and 85-dB primaries. On the average, however, across all frequency-amplitude stimulus conditions, maximal DPE amplitude was best obtained using an f2/f1 ratio of 1.23. Overall, DPE findings describing the outcome of varying level, frequency separation, and frequency region of primary tones were consistent with those reported in the psychophysical literature for normal-hearing humans. [Work supported by NINCDS.]
Spontaneous oto-acoustic emission from a chinchilla ear following exposure to noise
Authors: Clark William W. , Solomonson Martha
Published: October 2005

A spontaneous oto-acoustic emission (SOAE) was observed in one chinchilla after two exposures to an octave band of noise (OBN) centered at 0.5 kHz, 95 dB SPL, each for 9 days. This SOAE, not present before the second exposure, was a narrow-band signal at 2.2 kHz that varied from 10–26 dB SPL across recording sessions. The SOAE has remained stable over the 3-year period since it was discovered. During the past year, this animal has been trained behaviorally so that detection and discrimination thresholds can be determined in the region near the SOAE. Measures of auditory sensitivity at quarter-octave intervals between 0.125 and 16.0 kHz revealed a hearing loss (re: normal chinchilla) of 22 dB centered at 2.37 kH2. However, thresholds determined at 10-Hz intervals between 1600 Hz and 2800 Hz showed that the SOAE was correlated generally with a region of enhanced sensitivity in the microstructure of the audiogram. However, in the immediate vicinity of the SOAE thresholds were elevated by 5–10 dB; addition of a tonal masker (2.2 kH2 at 5–20 dB SPL) had no effect on the shape of the audiogram. [Work supported by Grant OH 02128 from NIOSH.]
Interaural phase and level effects on binaural interaction component (BIC) of the brain-stem auditory evoked potential
Authors: Bopanna Ballachanda B. , Moushegian George
Published: October 2005

Electrophysiological studies have elegantly demonstrated that neurons in lower brain-stem nuclei are exquisitely sensitive to the parameters of sound that mediate localization and lateralization phenomena. In the present study, the binaural interaction component (BIC), derived from brain-stem auditory evoked potentials, was obtained using low-frequency stimuli with various combinations of time and level differences delivered through earphones. The aim has been to determine whether these volume-conducted multineuronal responses reveal any of the neural mechanisms of lateralization. The findings show that characteristics of the binaural interaction component, e.g., latency, amplitude, and waveform morphology, evoked by low-frequency tone bursts, are differentially altered with changes in interaural phase. The effects on the binaural interaction component with interaural level differences were also substantial but not similar to the changes produced with phase. From this research, it has become apparent that, given appropriate recording and stimulating parameters, many nuances of binaural hearing may be neurophysiologically addressed in studies of volume-conducted evoked and derived potentials.
AP and ABR tuning curves: A comparative study
Authors: Elshintinawy Abdelhamid A. , Abbas Paul J.
Published: October 2005

Whole-nerve action potential (AP) and auditory brain-stem response (ABR) were recorded from anesthetized eats. Response amplitude and latency to a probe stimulus were measured and tuning curves were constructed using three masking paradigms; forward, simultaneous (a tone burst masker overlapping the probe), and continuous (a continuous masker tone). AP and ABR tuning curves were generated on the basis of criterion changes in both amplitude and latency of the response. Within each of the masking techniques, tuning curves developed from the amplitude and latency criterion changes of the AP and the ABR showed no significant differences. The only significant differences were measured across masking conditions. Forward masking tuning curves were found to have steeper high-frequency slopes, higher Q 10 values, and lower sensitivity indicies (defined as the difference between probe level and the level at the tip of the tuning curve). Low-frequency slopes and the tip-to-tail ratios showed no significant differences. [Work supported partially by the Deafness Research Foundation.]
Fiber tract model of auditory brain-stem response generation
Authors: Özdamar Özcan , Delgado Rafael E. , Grandori Ferdinando
Published: October 2005

A fiber tract model for the generation of auditory brain-stem responses (ABRs) is developed using volume conducted potentials in a spherical conducting medium. This model proposes that the fast components of the ABR are generated by the synchronized propagation of the action potentials traveling along the auditory brain-stem pathways. The model represents an action potential with up to 100 current dipoles traveling along a pathway corresponding to a known auditory brain-stem tract. Coordinates of the major fiber tracts are obtained from human brain atlases and adapted to a spherical head model. Computations assuming classical interconnections between brain-stem nuclei show that such synchronously propagating action potentials can generate waveforms similar to recorded ABRs. According to this model, positive peaks correspond to the depolarizing wave front of the action potential while negative valleys are generated with the repolarizing phase.
Steady-state evoked potentials in sleeping humans to continuous modulated tones
Authors: Cohen Lawrence T. , Rickards Field W.
Published: October 2005

At a previous meeting of the society, Rickards and Clark [J. Acoust. Soc. Am. Suppl. 1 72, S54(1982)] showed that steady-state evoked potentials could be recorded from alert humans in response to amplitude-modulated tones over a wide range of modulation frequencies. A subsequent paper has shown that, while there is an amplitude response maximum for alert subjects at a modulation rate of approximately 40 Hz and this frequency is thus appropriate for optimum threshold detection, different circumstances apply for sleeping subjects. Sleeping subjects differ from alert subjects in both amplitude response and background EEG noise, as functions of modulation frequency. A detection efficiency function reveals that during sleep the optimum modulation frequency, dependent on stimulus carrier frequency, lies well above 40 Hz. For lower carrier frequencies a peak occurs at about 90 Hz, while at higher frequencies the optimum modulation frequency is as high as 150 Hz. These higher modulation rates allow more efficient detection than does 40 Hz. Stimuli with high modulation rates have been used successfully with sleeping subjects including neonates.
AGC behavior of a recovery model for auditory neuron firings
Authors: Wilson Timothy A.
Published: October 2005

In a recovery model for auditory neuron firings [Westerman and Smith. J. Acoust. Soc. Am. 81, 680–691 (1987); Johnson and Swami, J. Acoust. Soc. Am. 74, 493–501 (1983)], the firing history manifests itself as a reduction in the instantaneous probability of a neural event. In this paper, it is shown that the ensemble behavior of such a model may be interpreted as that of a feedback automatic gain control (AGC). The AGC input is the excitation function and its output is the ensemble-average firing rate. The impulse response of the gain-control filter is a superposition of time-invariant and time-varying components that are related to the recovery function's absolute- and relative-refractory intervals, respectively. In response to a steplike input, the model's output resembles the firing-rate response of an auditory neuron to a tone burst: Both contain an exponentially decaying rapid transient whose time constant decreases as the input size increases. [Work supported by DARPA under contract N00014-82-K-0727, monitored through the Office of Naval Research.]
Evaluation of an eight-channel scala tympani electrode with single unit recording in the auditory nerve
Authors: Liang David H.
Published: October 2005

In order for a multichannel cochlear prosthesis to be more effective than a single-channel prosthesis, the different channels of the stimulating electrode must be able to activate separate populations of the neurons in the auditory nerve. Earlier animal studies [C. van den Honert and P. Stypulkowski, Hear. Res. 14, 225–243 (1984); H. S. Lusted, Ph.D. thesis, Stanford University, 1980] have resulted in conflicting conclusions about whether this occurs for monopolar stimulation. To address this question, an eight-channel electrode array was acutely placed in the scala tympani of seven cats. Recordings were then made in the VIIIth nerve, of single unit responses to electrical stimulation from each of the channels in the array. For each unit isolated, threshold current for biphasic monopolar stimulation was determined for each of the electrode channels. Some units were found to be highly selective in their response to the different channels of the electrode array, with the most effective electrode having a threshold lower than an adjacent electrode by up to a factor of 5 times. Adjacent electrodes were either 1.0 or 1.5 mm apart. Other units were found not to be very selective in their response. This suggests that some degree of spatial selectivity is achievable with monopolar stimulation. [Work supported by NIH.]
Effect of acoustic tone perception on several higher modes of brain-generated electromagnetic waves: Preliminary evidence
Authors: Stocklin Philip L.
Published: October 2005

Brain-generated microwaves were detected and measured for each of two subjects for several higher modes in the frequency range of the 7th–13th primary mode of the adult human brain (1200–1900 MHz). Differences in mode amplitude of 5–8 dB were measured with a loud acoustic tone stimulus ON and OFF. Higher mode amplitude change occurs immediately upon tone stimulus start or stop. In order to increase higher mode power well above ambient noise, a zero mode “pumping” procedure was used. Intersubject and control subject comparisons show no acoustic/ microwave crosstalk, either mechanical or electrical. No mode activity was measureable by any subject in the mode frequency region of any other subject, with or without zero mode pumping. [Work sponsored by Mentec, Inc.]
Perception of vowel nasalization in VC contexts: A cross-language study
Authors: Stevens Kenneth N. , Andrede Amália , Viana M. Céu
Published: October 2005

A series of stimuli ranging between [tΛtΛ], [tΛ̄tΛ], and [tΛntΛ] were synthesized by systematically manipulating (1) the duration of nasalization in the vowel [Λ], (2) the amount of nasalization in the vowel, and (3) the duration of the nasal murmur following the vowel. The stimuli were presented to native speakers of Portuguese, English, and French, which differ with respect to the occurrence of nasal vowels in their phonological systems. The listeners were asked to judge, for each stimulus, (1) the presence or absence of nasalization and (2) the adequacy of the stimulus as a natural utterance with respect to its nasalization. The different language groups gave similar responses with regard to the presence or absence of nasalization. However, judgments of the naturalness of the stimuli in the different languages depend on the temporal characteristics. French listeners preferred a longer duration of nasalization in the vowel and were indifferent to the presence of murmur; English listeners preferred some murmur and accepted briefer nasalization in the vowel; and Portuguese responses were intermediate. Preliminary acoustic data from utterances in the three languages are in accord with these perceptual findings.
On the identification of Spanish voiced stops
Authors: Gurlekian Jorge A. , Guirao Miguelina , Franco Horacio
Published: October 2005

Experiments were conducted to examine the interaction between relevant acoustic features of Spanish /b,d,g/ emitted with /a/ in CV syllables and VCV combinations with the first or second vowel with stress. Duration of steady and transitional vowel segments and the closure duration were systematically segmented at particular time intervals. The entire sequences and spliced segments were presented to native Spanish speakers for identification. Results were presented as a ratio between different closure durations and the number of vocalic periods required for the identification of the stop. Different ratios were obtained for each consonant in the CV syllable. When the closure portion was removed completely, the unvoiced counterparts were accurately perceived. This was not true for /g/, where the absence of the burst avoided the shifting to /k/. For the VCVs when the closure portion was entirely removed and the remaining parts were rejoined, the stops—approximants in this context—were still identified. These results showed that /b/ and /d/ identification was cued by a voiced portion preceding the transition of the following vowel. Primary features for these sounds were located in the transition edges—final and initial—which overlapped both vowel and consonant information.