bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of extraneous sounds on the perceptual estimation of first-formant frequency in vowels
Authors: Roberts Brian , Moore Brian C. J.
Published: October 2005

The contribution of extraneous sounds to the perceptual estimation of the first-formant (F1) frequency of voiced vowels was investigated using a continuum of vowels perceived as changing from /I/ to /q/ as F1 was increased. Any phonetic effects of adding extraneous sounds were measured as a change in the position of the phoneme boundary on the continuum. Experiments 1–5 demonstrated that a pair of extraneous tones, mistuned from harmonic values of the fundamental frequency of the vowel, could influence perceived vowel quality when added in the F1 region. Perceived F1 frequency was lowered when the tones were added on the lower skirt of F1, and raised when they were added on the upper skirt. Experiments 6 and 7 demonstrated that adding a narrow-band noise in the F1 region could produce a similar pattern of boundary shifts, despite the differences in temporal properties and timbre between a noise band and a voiced vowel. The data are interpreted using the concept of the harmonic sieve [Duifhuis et al., J. Acoust. Soc. Am. 71, 1568–1580 (1982)]. The results imply a partial failure of the harmonic sieve to exclude extraneous sounds from the perceptual estimation of F1 frequency. Implications for the nature of the hypothetical harmonic sieve are discussed.
Loudness relations for individuals and groups in normal and impaired hearing
Authors: Hellman Rhona P. , Meiselman Carol H.
Published: October 2005

Individual and group loudness relations were obtained at a frequency in the region of impaired hearing for 100 people, 98 with bilateral cochlear impairment. Slope distributions were determined from absolute magnitude estimation (AME) and absolute magnitude production (AMP) of loudness; they were also derived from cross-modality matching (CMM) and AME of apparent length. With respect to both the means and the individual slope values, the two distributions closely agree. More than half of the measured deviations are less than 20%, with an overall average of −1.5%, meaning that transitivity is preserved for bilaterally impaired individuals. Moreover, over the stimulus range where cochlear impairment steepens the loudness function, both the group means and the individual slope values are clearly larger than in normal hearing. The results also show that, for groups of people with approximately similar losses, the standard deviation is a nearly constant proportion of the mean slope value giving a coefficient of variation of about 27% in normal and impaired hearing. This indicates, in accord with loudness matching, that the size of the slopes depends directly on the degree of hearing loss. The results disclose that loudness measurements obtained by magnitude scaling are able to reveal the operating characteristic of the ear for individuals.
How much masking is informational masking?
Authors: Lutfi Robert A.
Published: October 2005

It is estimated that 22% of the masking observed in many traditional tone-in-noise detection experiments is due to uncertainty associated with trial-to-trial variation in the noise waveform.
Limits of auditory pattern discrimination for patterns with various durations and numbers of components
Authors: Watson Charles S. , Foyle David C. , Kidd Gary R.
Published: October 2005

In three experiments, listeners’ abilities to detect changes in randomly generated tonal sequences were determined for sequences or ‘‘patterns’’ ranging in total duration from 62.5 62.5 ms to 2 s. Experiment 1 utilized an adaptive-tracking procedure, with n, the number of pattern components, as the dependent variable, and included a variety of spectral and temporal discrimination tasks with isochronous patterns. When the to-be-detected change was the only variation on a given dimension (e.g., the presence or location of a brief pause), patterns were discriminable when the absolute duration of the changed element, or pause, exceeded a critical value. However, when each pattern component varied on the dimension of the to-be-detected change (e.g., frequency), discriminability was strongly related to the number of tones in the pattern, and only weakly to the durations of either the target components or the total pattern. This dependence of discrimination performance on n was also demonstrated with anisochronous patterns in experiment 2. Experiment 3 revealed the same dependence of performance on the number of components per pattern as did experiments 1 and 2, but with Δf/f as the dependent variable, rather than n. The number of pattern components and the proportional duration of the target components, relative to total pattern duration, were confounded in these experiments. Additional research is therefore required to determine whether number or proportional target-tone duration is the primary determinant of pattern discriminability.
Modal sampling method for the vibration study of systems of high modal density
Authors: Guyader J. L.
Published: October 2005

This paper presents a method to predict the vibration response of a group of modes, using a sample of modes of the group. The accuracy of the prediction can be improved when increasing the size of the sample. Numerical calculations made on a beam, driven in longitudinal motion, show the ability of the method to reconstitute the energy response of a group of modes including resonant modes, with a sample of a number of modes close to that in the effective damping bandwidth.
Absorption of ultrasonic waves in aqueous solutions of N-methylacetamide and zinc chloride
Authors: Miecznik Piotr
Published: October 2005

Measurements of the absorption coefficient of ultrasonic waves have been made within the frequency range of 10–100 MHz in aqueous solutions of N-methylacetamide (NMAA) and zinc chloride (ZnCl2). The method used to prepare quasi-two-component solutions permitted a change in the ratio of the number of amide molecules to electrolyte molecules, given a constant number of water molecules. The results indicate the occurrence of a single relaxational process in the solutions under investigation and the frequency range adopted. On the basis of the theory of relaxational absorption of sounds, relaxation parameters as well as the enthalpy of activation of the solution in question, which was 16.4 kJ/mol, have been calculated. The character of the relaxational process observed was determined on the basis of the analysis of relaxational curves. The discovered relaxational process in H2O–NMAA–ZnCl2 was ascribed to the formation and disintegration of ‘‘solvatomers’’ composed of [NMAA Zn(H2O)3]2+.
The stability of resonant vibration to temperature change in modal vibration control of large ultrasonic tools using wave-trapped horns
Authors: Adachi Kazunari
Published: October 2005

The stability of resonant vibration to temperature change is a crucial point to consider the feasibility of the method of modal vibration control of large ultrasonic tools using ‘‘wave-trapped horns.’’ The stability for aluminum tools through theoretical consideration and numerical simulations is evaluated. As a result, the vibration modes are found inherently quite stable to the temperature change expected to occur in ordinary working environments.
Three-dimensional numerical modeling of geoacoustic scattering from seafloor topography
Authors: Burns Daniel R. , Stephen Ralph A.
Published: October 2005

A three-dimensional (3-D), second-order finite-difference method was used to create synthetic seismograms for wave propagation in heterogeneous media in order to investigate the scattering of elastic and acoustic energy due to topography on the seafloor. The method uses a fully staggered grid in Cartesian coordinates as developed by Virieux [Geophysics 51, 889–901 (1986)]. Numerical results were generated for two models: a linear fault scarp on the seafloor, and a flat seafloor containing a rectangular channel. Wave-front snapshots allow the scattering and focusing of different wave modes with direction to be visualized. Compressional and shear wave backscattering from the sides of the features can be seen together with the trapped compressional wave energy propagating inside the channel. The results illustrate the effects of out of the plane scattering due to simple seafloor topographic features.
Acoustic response of a rectangular levitator with orifices
Authors: El-Raheb Michael , Wagner Paul
Published: October 2005

The acoustic response of a rectangular cavity to speaker-generated excitation through waveguides terminating at orifices in the cavity walls is analyzed. To find the effects of orifices, acoustic pressure is expressed by eigenfunctions satisfying Neumann boundary conditions as well as by those satisfying Dirichlet ones. Some of the excess unknowns can be eliminated by point constraints set over the boundary, by appeal to Lagrange undetermined multipliers. The resulting transfer matrix must be further reduced by partial condensation to the order of a matrix describing unmixed boundary conditions. If the cavity is subjected to an axial temperature dependence, the transfer matrix is determined numerically.
Comments on ‘‘An exact ray theoretical formulation of the Helmholtz equation’’ [J. Acoust. Soc. Am. 8
6, 234–246 (1989)]
Authors: Floyd Edward R.
Published: October 2005

Differences between ‘‘exact rays’’ and ‘‘rigorous rays’’ are noted.
Stimulus order effects in vowel discrimination
Authors: Repp Bruno H. , Crowder Robert G.
Published: October 2005

In same–different discrimination tasks employing isolated vowel sounds, subjects often give significantly more ‘‘different’’ responses to one order of two stimuli than to the other order. Cowan and Morse [J. Acoust. Soc. Am. 79, 500–507 (1986)] proposed a neutralization hypothesis to account for such effects: The first vowel in a pair is assumed to change its quality in memory in the direction of the neutral vowel, schwa. Three experiments were conducted using a variety of vowels and some initial support for the hypothesis was obtained, using a large stimulus set, but conflicting evidence with smaller stimulus sets. Rather than becoming more similar to schwa, the first vowel in a pair seems to drift toward the interior of the stimulus range employed in a given test. Several possible explanations are discussed for this tendency and its relation to presentation order effects obtained in other psychophysical paradigms is noted.
Classification of audiograms by sequential testing using a dynamic Bayesian procedure
Authors: Özdamar Özcan , Eilers Rebecca E. , Miskiel Edward , Widen Judith
Published: October 2005

A new method for estimating audiograms using behavioral responses is presented. The method is based upon a modification of the Bayesian probability formula in which an outcome is predicted from a static set of events. In the new method, classification of audiograms by sequential testing (CAST), the probabilities of occurrence of audiogram patterns are dynamically updated according to the outcome of each test trial. Computer simulation using an infant response model suggests that the procedure is efficient, sensitive, and specific.
Electrically evoked whole-nerve action potentials: Parametric data from the cat
Authors: Brown Carolyn J. , Abbas Paul J.
Published: October 2005

In a companion paper [Brown et al., J. Acoust. Soc. Am. 88, 1385–1391 (1990)], a method for recording the electrically evoked whole-nerve action potential in human cochlear implant users was reported. The procedure for recording the response requires that two biphasic current pulses, a ‘‘masker’’ and a ‘‘probe,’’ be presented at a rate and level sufficient to drive the auditory nerve into a refractory state. The present study was designed to assess the sensitivity of that recording technique to variations in stimulation parameters. The experiments described in this paper demonstrate that: (1) the EAP as recorded in the cat is triphasic and is defined by two negative peaks occurring at latencies of approximately 0.26 and 0.82 ms; (2) EAP amplitude is independent of the level of the masker stimulus for current levels equal to or greater than the current level of the probe stimulus; and (3) the time course of recovery of the EAP from the refractory state is stable over a range of both probe and masker current levels.
Edge effect on radiation efficiency of a baffled beam below the critical frequency
Authors: Peng H. , Banks-Lee P.
Published: October 2005

The radiation efficiency of a beam is theoretically determined from the total acoustic power radiated from the vibrating surface. The beam is supported in an infinite baffle, with edges constrained by either rotational or translational springs. Asymptotic solutions are derived for frequencies well below the critical frequency (KL≪1). In the range of KL<1, the asymptotic solutions are validated by numerical evaluation. For comparison, the low-frequency solutions are normalized by dividing them by the radiation efficiency of a beam with hinged supports. Numerical results show that a beam with edges constrained by soft springs may generate higher radiation efficiency than one with edges constrained by stiff springs. For a beam with edges constrained by translational springs, the maximum value of normalized efficiency ratio asymptotically approaches 2 as the mode number tends to infinity. For a beam with edges constrained by rotational springs, the radiation may be higher than that of a clamped beam. This phenomenon exists only for low-order modes.
A new integral equation formulation for an axisymmetric structure
Authors: Sarkissian Angie
Published: October 2005

A new method is developed to compute the acoustic field outside an axisymmetric structure from the normal velocity values on the surface. Surface pressure and normal velocity are expanded in a series of functions that are orthonormal on the surface of the structure and have a constant ratio of pressure to normal derivative of pressure at vanishing frequency. The Helmholtz integral equation is next used to compute the field everywhere outside the structure. The method is tested by applying it to scattering from a rigid cylinder with hemispherical endcaps. The series is shown to converge very rapidly.
On the linearity of the momentum equation for progressive plane waves of finite amplitude
Authors: Hamilton Mark F. , Blackstock David T.
Published: October 2005

This Letter is primarily in response to the Letter to the Editor by G. M. Tarkenton entitled ‘‘Remarks on ‘On the coefficient of nonlinearity β in nonlinear acoustics’ ’’ [J. Acoust. Soc. Am. 88, XXXX–XXXX (1990)]. It is reaffirmed that for progressive plane waves, the momentum equation contributes nothing at second order to the expressions for the coefficient of nonlinearity and finite amplitude propagation speed.
Subjective evaluation of acoustic properties of concert halls based on their impulse response
Authors: Hojan Edward , Pösselt Christoph
Published: October 2005

Impulse responses, binaurally recorded using an artificial head, of six European concert halls have been convolved with selected signals of music and speech. Acoustic signals thus obtained have been evaluated subjectively. Questionnaire techniques with semantic differential scales have been used that reflect four perceptual attributes: ‘‘clarity,’’ ‘‘sharpness of localization,’’ ‘‘spaciousness,’’ and ‘‘overall impression.’’ The greatest correlation among perceptual attributes has been obtained between sharpness of localization and clarity and the smallest for spaciousness and overall impression. In the ranking of concert halls, the highest rank has been awarded to the Concertgebouw in Amsterdam.
The power radiated by a vibrating body in an acoustic fluid and its determination from boundary measurements
Authors: Borgiotti Giorgio V.
Published: October 2005

The power radiated into a specified angular sector by a vibrating object immersed in a fluid is expressed as a quadratic functional of the boundary normal velocity field. The diagonalization of the functional, obtained through the singular value decomposition of its discretized version, identifies a set of orthonormal boundary velocity patterns, each corresponding to a far-field pattern belonging to a set of functions orthonormal in the angular sector of interest. Any boundary normal velocity field can be represented as a linear superposition of the orthonormal patterns. The velocity patterns having high radiation efficiencies form a subset, whose dimension depends upon the object boundary shape and size in wavelengths. The other velocity patterns do not radiate efficiently and contribute mainly to the evanescent field in the neighborhood of the object. Assuming that some noise is present, only the radiation patterns associated with the efficiently radiating velocity patterns are observable in the far field. Therefore, the dimension of their set defines the number of degrees of freedom of the far field. The efficiently radiating velocity patterns constitute a set of spatial filtering functions, separating the radiating from the essentially nonradiating components of an arbitrary boundary normal velocity field.
Fourier synthesis of three-dimensional scattering in a two-dimensional oceanic waveguide using boundary integral equation methods
Authors: Fawcett John A. , Dawson Trevor W.
Published: October 2005

A numerical method is presented for computing the three-dimensional pressure field generated by compact harmonic sources in a two-dimensional stratified acoustic waveguide. This method can serve to model acoustic scattering from ridgelike bathymetry, or surface features such as ice ridges, in a realistic oceanic waveguide model. The basic technique entails synthesizing the three-dimensional solution by using Fourier transform methods based on a sequence of two-dimensional problems. Numerical results from computations based on a simple cosine-bell ridge model and a more complex ice model are presented, and a comparison with the analogous strictly two-dimensional model is also considered.
On the influence of different parameters on heterogeneous shock cavitation
Authors: Rein Martin , Meier Gerd E. A.
Published: October 2005

The sudden rupture of liquids behind strong tension waves, which is significantly affected by cavitation nuclei, is called heterogeneous shock cavitation. The process of cavitation is described by a microbubble model, taking into account the dynamics of the individual cavitation nuclei. The effect of different parameters, such as the amplitude and steepness of the tension wave and the properties of the liquid on the characteristics of heterogeneous shock cavitation, is numerically investigated. The number density of cavitation nuclei, but not their size, turns out to play a predominant role for heterogeneous shock cavitation within wide bounds.
Acoustic streaming in a rotating fluid
Authors: Whitworth Glenn
Published: October 2005

Acoustic streaming theory is derived that is applicable to a fluid that is slow moving in a reference frame that rotates with a constant angular velocity Ω. A simplified streaming equation is obtained for the special case in which the acoustic angular frequency ω is large relative to Ω, and the change in fluid density due to rotation alone is negligible. For this special case it is shown that the ‘‘driving force’’ for the acoustic streaming is independent of Ω. Thus if no acoustic streaming is present in a fluid system that is stationary, then no steady-state acoustic streaming is predicted for a similar system that rotates with constant angular velocity. For a system in which acoustic streaming is present, the flow behavior depends on the relative magnitudes of the Coriolis forces and the viscous forces. If the Ekman number is large (that is, the viscous force dominates) then the predicted flow is identical to that which would exist in a stationary system. If, on the other hand, the Ekman number is small then the Coriolis force dominates and the component of flow in the direction of the axis of rotation can be much smaller in the rotating system than in a similar system at rest.
A general theory for wave field extrapolation in bounded and unbounded homogeneous media
Authors: Doelman N. J.
Published: October 2005

In this article wave field extrapolation in bounded and unbounded homogeneous media is studied. A generally applicable description for any type of homogeneous medium with arbitrary boundary conditions is developed. The extrapolation theory is based on the Kirchhoff integral in the frequency domain. In several steps this Kirchhoff integral is transformed into a straightforward extrapolation expression. First, Green’s function is expanded in an infinite series of eigenfunctions belonging to the lateral directions. Second, the wave field extrapolation operation is diagonalized by choosing a base of eigenfunctions for the Hilbert function space. Further facilitation of the extrapolation problem for both bounded and unbounded homogeneous media is achieved by employing one-way wave equations. These one-way wave equations decompose a wave field into a downstream and an upstream traveling wave field. The final result is a comprehensive description of both forward and inverse wave field extrapolation, which can easily be applied to quite complicated extrapolation problems in any type of homogeneous medium.
Effects of fluctuating noise and interfering speech on the speech-reception threshold for impaired and normal hearing
Authors: Festen Joost M. , Plomp Reinier
Published: October 2005

The speech-reception threshold (SRT) for sentences presented in a fluctuating interfering background sound of 80 dBA SPL is measured for 20 normal-hearing listeners and 20 listeners with sensorineural hearing impairment. The interfering sounds range from steady-state noise, via modulated noise, to a single competing voice. Two voices are used, one male and one female, and the spectrum of the masker is shaped according to these voices. For both voices, the SRT is measured as well in noise spectrally shaped according to the target voice as shaped according to the other voice. The results show that, for normal-hearing listeners, the SRT for sentences in modulated noise is 4–6 dB lower than for steady-state noise; for sentences masked by a competing voice, this difference is 6–8 dB. For listeners with moderate sensorineural hearing loss, elevated thresholds are obtained without an appreciable effect of masker fluctuations. The implications of these results for estimating a hearing handicap in everyday conditions are discussed. By using the articulation index (AI), it is shown that hearing-impaired individuals perform poorer than suggested by the loss of audibility for some parts of the speech signal. Finally, three mechanisms are discussed that contribute to the absence of unmasking by masker fluctuations in hearing-impaired listeners. The low sensation level at which the impaired listeners receive the masker seems a major determinant. The second and third factors are: reduced temporal resolution and a reduction in comodulation masking release, respectively.
Binaural masking experiments using noise maskers with frequency-dependent interaural phase differences. I: Influence of signal and masker duration
Authors: Kohlrausch Armin
Published: October 2005

In this paper previous experiments on auditory filter shapes in binaural masking experiments [A. Kohlrausch, J. Acoust. Soc. Am. 84, 573–583 (1988)] are extended to a wider range of masker and signal durations. The masker was a dichotic broadband noise with frequency-dependent interaural parameters. The interaural phase difference of the masker was 0 below 500 Hz and π above 500 Hz. Signal frequency varied between 200 and 800 Hz, and the signal was presented either monaurally (Sm) or binaurally in antiphase (Sπ). In the first experiment, the masker duration was fixed at 500 ms and signals of 250 and 20 ms were used. In the second experiment, the signal duration was fixed at 20 ms, and the masker duration was reduced to 25 ms. The results from both experiments are consistent with studies using No or Nπ maskers: The binaural masking level difference (BMLD) increases slightly for shorter test signals and decreases strongly for short maskers. The BMLD patterns of the first experiment are well described by the auditory-filter model derived for stationary test signals, if the additional influence of ‘‘off-frequency listening’’ for the short test signal is taken into account. The BMLDs resulting from the second experiment (25-ms masker), however, are much lower than predicted by this filter model. This outcome supports previous observations that binaural unmasking becomes less effective for very short masker durations and indicates that this effect is even stronger for maskers with a complex structure of interaural parameters.
Coherence lengths of seafloor noise: Effect of ocean bottom structure
Authors: Schreiner Anthony E. , Dorman LeRoy M.
Published: October 2005

Results are reported from an experiment, conducted in 1987, in which an ocean bottom seismograph array of 150-m aperture and minimally redundant design was used to record the ambient noise in deep water off the California coast. The minimum interelement spacing among the nine instruments was 8 m. The coherence lengths observed imply that the noise field in the 0.05- to 5-Hz band are fundamental and higher-mode Rayleigh/Stoneley/Scholte waves and the relative amplitudes of the modes imply that the excitation occurs within 20 km of the array. These observations imply that the noise energy is scattered into the seafloor waveguide at the boundaries of the sediment pond in which the array was sited. The implications for sub-bottom sensors are discussed.
Finite-amplitude ultrasonic measurements of polyethylene oxide and polyacrylamide solutions
Authors: Milliken William J. , Powell Robert L.
Published: October 2005

Experiments on the propagation of planar acoustic waves in aqueous solutions of high-molecular-weight polyethylene oxide and polyacrylamide are discussed. The acoustic absorption of the solutions was determined at 2.5 and 7.5 MHz, and the growth and decay of the amplitude of the second-harmonic component generated by the 7.5-MHz source was measured. It was found that the absorption and second-harmonic amplitude generally increased with both concentration and molecular weight. However, the absorption was found to be much less than in Newtonian fluids with equal zero-shear-rate properties (i.e., viscosity, density, and small-signal wave speed). Additionally, the frequency dependence of the data indicate that a relaxation process occurs in both polymers at a characteristic frequency in the range 1–10 MHz. At low polymer concentration, the second-harmonic amplitude was less than that found in water under similar experimental conditions.
On the frequency separation of simultaneously evoked otoacoustic emissions’ consecutive extrema and its relation to cochlear traveling waves
Authors: Zwicker Eberhard
Published: October 2005

Simultaneously evoked otoacoustic emissions (SEOAEs) were recorded in 24 ears of 17 normal-hearing subjects. The data are pooled as frequency separations between neighboring maxima expressed in critical-band rate. The distribution shows a clear maximum at 0.4 Bark corresponding to a distance of about 0.5 mm along the basilar membrane. This characteristic value is discussed using related data from an analog model of nonlinear cochlear preprocessing with active feedback and lateral coupling. Results indicate that the phase characteristic of the traveling wave in the cochlea has a slope of 180° per 0.4 Bark (0.5 mm) near the respective characteristic place. A frequency shift corresponding to a traveling-wave-place shift of 0.5 mm results in an SEOAE-phase shift of two times 180°, i.e., 360° phase shift, as found for neighboring SEOAE maxima or minima.
The representation of the spectra and fundamental frequencies of steady-state single- and double-vowel sounds in the temporal discharge patterns of guinea pig cochlear-nerve fibers
Authors: Palmer A. R.
Published: October 2005

Psychophysical results using double vowels imply that subjects are able to use the temporal aspects of neural discharge patterns. To investigate the possible temporal cues available, the responses of fibers in the cochlear nerve of the anesthetized guinea pig to synthetic vowels were recorded at a range of sound levels up to 95 dB SPL. The stimuli were the single vowels /i/ [fundamental frequency (f0) 125 Hz], /a/ (f0, 100 Hz), and /c/ (f0, 100 Hz) and the double vowels were /a(100),i(125)/ and /c(100),i(125)/. Histograms synchronized to the period of the double vowels were constructed, and locking of the discharge to individual harmonics was estimated from them by Fourier transformation. One possible cue for identifying the f0’s of the constituents of a double vowel is modulation of the neural discharge with a period of 1/f0. Such modulation was found at frequencies between the formant peaks of the double vowel, with modulation at the periods of 100 and 125 Hz occurring at different places in the fiber array. Generation of a population response based on synchronized responses [average localized synchronized rate (ALSR): see Young and Sachs [J. Acoust. Soc. Am. 66, 1381–1403 (1979)] allowed estimation of the f0’s by a variety of methods and subsampling the population response at the harmonics of the f0 of the constituent vowel achieved a good reconstruction of its spectrum. Other analyses using interval histograms and autocorrelation, which overcome some problems associated with the ALSR approach, also allowed f0 identification and vowel segregation. The present study has demonstrated unequivocally that the timing of the impulses in auditory-nerve fibers provides copious possible cues for the identification of the fundamental frequencies and spectra associated with each of the constituents of double vowels.
Comment on ‘‘Near-grazing propagation above a soft ground’’ [J. Acoust. Soc. Am. 8
2, 1706–1711 (1987)]
Authors: Li K. M. , Attenborough K. , Heap N. W.
Published: October 2005

Makarewicz [J. Acoust. Soc. Am. 82, 1706–1711 (1987)] has proposed an interesting method for predicting the attenuation of the A-weighted sound-pressure level at long ranges from a point source above a locally reacting plane ignoring the influence of meteorological and topographical conditions. An error found in his derivation resulting from inconsistent use of his chosen sign convention for the time dependence is documented. Furthermore, use of a more versatile ground impedance model, namely, a two-parameter variable porosity model, is suggested. This enables a closed-form solution for minimizing the A-weighted mean-square sound pressure.
Measurement of the turbulent boundary layer wave-vector spectrum
Authors: Sherman Charles H. , Ko Sung H. , Buehler Barry G.
Published: October 2005

Wave-vector filter measurements have been made with the objective of improving quantitative knowledge of the flow excitation function. Two hydrophone arrays with the same number of elements but with different spacings were used. The more closely spaced array covers high-wavenumber characteristics of the convective region of the turbulent boundary layer pressure fluctuations, whereas the other array covers the lower-wavenumber region where contaminants associated with the experimental arrangement also usually exist. Measured results (dB re: 1 μPa2/Hz) are presented as amplitude contour plots as a function of the two wave-vector components at various frequencies. Wave-vector components associated with free-plate vibrations in the low-wavenumber domain were also identified in the results measured using the larger array.
Coarticulatory organization for lip rounding in Turkish and English
Authors: Boyce Suzanne E.
Published: October 2005

A number of studies, involving English, Swedish, French, and Spanish, have shown that, for sequences of rounded vowels separated by nonlabial consonants, both EMG activity and lip protrusion diminish during the intervocalic consonant interval, producing a ‘‘trough’’ pattern. A two-part study was conducted to (a) compare patterns of protrusion movement (upper and lower lip) and EMG activity (orbicularis oris) for speakers of English and Turkish, a language where phonological rules constrain vowels within a word to agree in rounding and (b) determine which of two current models of coarticulation, the ‘‘look-ahead’’ and ‘‘coproduction’’ models, best explained the data. Results showed Turkish speakers producing ‘‘plateau’’ patterns of movement rather than troughs, and unimodal rather than bimodal patterns of EMG activity. In the second part of the study, one prediction of the coproduction, model, that articulatory gestures have stable profiles across contexts, was tested by adding and subtracting movement data signals to synthesize naturally occurring patterns. Results suggest English and Turkish may have different modes of coarticulatory organization.
An improved formalism for wave scattering from rough surfaces
Authors: Milder D. Michael
Published: October 2005

The scattered field and its normal gradient obey a mutual linear relation at the scattering surface that is distinct from the physical boundary condition connecting either quantity to the incident radiation. On a moderately rough surface this relation can be represented by an operator whose series expansion in surface slope converges nicely even for large values of the Rayleigh parameter. This allows the Helmholtz integral for scattering amplitude to be written as a series of readily computable terms, one or two of which provide good approximations for surfaces too irregular for the usual Bragg expansion. This formulation reproduces the Bragg series for small surface elevations, and in the limit of low roughness wavenumber gives the Kirchhoff approximation with an explicit correction term in surface curvature. The usual results for a composite surface also emerge naturally. On several test profiles the method produces better overall accuracy than other multiscale approximations, at comparable efficiency.
A study on the automatic recognition of voiceless unaspirated stops
Authors: Wang Hsiao-Chuan , Liu Lih-Cherng , Lee Lee-Min , Chang Yueh-Chin
Published: October 2005

This paper presents a method of feature extraction for the automatic recognition of voiceless unaspirated stop consonants in Mandarin speech. The features are derived from the spectrographic acoustic patterns of syllable-initial voiceless unaspirated stops /p,t,k/, which include the burst spectrum, the formant transition, and the voice onset time. A normalization process for the second and the third formants at the voice onset is proposed. Based on these derived features, Bayes classifiers and a layered neural net are applied to classify the places of articulation of these stop consonants. The experiments show that the derived features are robust and efficient for speaker-independent speech recognition, and the neural net is a preferable choice in the classification of these stops in multiple contexts.
Development of the filtered-U algorithm for active noise control
Authors: Eriksson L. J.
Published: October 2005

The filtered-X algorithm developed by Widrow and Burgess is an alternate form of the least-mean-square (LMS) algorithm for use when there are transfer functions in the auxiliary path following the adaptive filter. To ensure convergence of the algorithm, the input to the error correlators is filtered by a copy of these auxiliary path transfer functions. More recently, the author has presented a new approach to active noise control in the presence of acoustic feedback that uses an infinite impulse response (IIR) filter structure with an alternate form of the recursive least-mean-square (RLMS) algorithm. This algorithm may be described as a filtered-U algorithm since it uses a copy of the auxiliary path transfer functions to filter the generalized input vector U to the error correlators of both the direct and recursive elements of the filter to ensure convergence. The relationship of the filtered-U to the filtered-X algorithm and other earlier concepts is discussed.
Adaptive postbeamformer interference canceler with improved performance in the presence of broadband directional sources
Authors: Godara Lal C.
Published: October 2005

A postbeamformer interference canceler (PIC) is a beam space processor that processes the signals derived from an antenna array by forming two beams using fixed beamforming weights. One beam, referred to as the signal beam, is formed to have a fixed response in the known signal direction. The processed output of the second beam, referred to as the interference beam, is subtracted from the output of the signal beam to form the output of the PIC. In the presence of broadband directional sources, the formation of a beam is usually carried out by a set of steering delays followed by a weight and sum network. For this case, the processing of the interference beam output is carried out by a tapped delay line filter. When the two beams of the PIC are formed using conventional weights and the tapped delay line filter weights are adjusted to minimize the mean output power of the PIC, a substantial amount of the signal gets suppressed. It is due to the presence of signal component in the interference channel. This paper considers a frequency domain structure of the PIC (FDPIC) in the presence of broadband directional sources; derives conditions required for the performance of the FDPIC to be equal to the performance of the time-domain structure of the PIC (TDPIC); presents an algorithm to calculate the fixed weights of the two beams at each frequency bin such that the FDPIC maintains a specified frequency response in the signal direction and its optimized performance is better than that of the TDPIC using conventional beam weights; and suggests a scheme to select a gradient step size, which allows the misadjustment of the convergence time constant of the iterative gradient algorithm to be specified.
Frequency resolution as a function of hearing threshold level and age
Authors: Lutman Mark E. , Gatehouse Stuart , Worthington Andrew G.
Published: October 2005

Frequency resolution ability was measured using a psychoacoustical tuning curve (PTC) or a notch-noise technique in two population samples. The first sample incorporated 1764 subjects with various degrees of sensorineural hearing impairment and ranging in age from 17–80 years. The second sample included 240 subjects aged between 50 and 75 years, carefully balanced in terms of impairment and age to avoid confounding between these two variables. In both samples, frequency resolution ability declined with increasing hearing threshold level (HTL), as measured by either method. In a subsample tested with both methods, the correlation between the two was only modest. After accounting for HTL, there was a minor dependence of frequency resolution on age, older subjects having poorer frequency resolution once HTL had been accounted for. No addition to the explained variance was achieved by taking sex, occupational group, or audiogram slope into account. Despite the documented reproducibility of the measures, much of the variance in the frequency resolution measurements remained unrelated to HTL or age.
The problem of energy conservation in one-way models
Authors: Porter Michael B. , Jensen Finn B. , Ferla Carlo M.
Published: October 2005

It is shown that the standard stair-step representation of a sloping bottom may result in significant prediction errors. In fact, current parabolic equation implementations are not energy conserving. The problem is shown to derive from the approximate treatment of the interface conditions at vertical boundaries along the stair steps. Several improved interface conditions are proposed.
Sound generation in the vicinity of the sea surface: Source mechanisms and the coupling to the received sound field
Authors: Cato Douglas H.
Published: October 2005

This paper presents a theory of the mechanisms of sound generation in fluids containing moving fluid interfaces, i.e., discontinuities in density and sound speed, following the approach of Lighthill [Proc. R. Soc. London Ser. A 211, 564–587 (1952)]. It is shown that in addition to the expected volume distributions of quadrupoles, motion of the discontinuities radiate sound equivalent to that from distributed monopoles and dipoles in place of the surfaces. These sources account both for the generation of sound and for the effect of the surfaces on the radiation of that sound. The results are applied to sound generation in the vicinity of the sea surface. All sources are inherent in the theory. The second part of this paper derives a direct relationship between the sound pressure spectrum in the ocean and the frequency wave-number spectra of the near surface fluid processes responsible for generating the sound, on the assumption that these fluid processes are statistically homogeneous in the horizontal plane. The effects of refraction and bottom reflections are ignored. The results are given in terms of “coupling factors” that are measures of the extent to which the source field copules to the received sound field. The coupling factors are evaluated and the results give some insight into the source characteristics required to ensonify the far field.
Forward masking by maskers of uncertain frequency content
Authors: Neff Donna L.
Published: October 2005

Large amounts of simultaneous masking can be produced when the frequency content of multicomponent maskers is changed with each presentation. This study examined whether such masker uncertainty also influences forward masking. The forward maskers were a 1000-Hz sinusoid, a broadband noise, and tonal complexes composed of 2–100 sinusoids drawn at random from a 300 to 3000-Hz range. A 10-ms signal at 1000 Hz followed the offset of 200-ms, 60 to 80-dB maskers with delays of 4–32 ms. For comparison, simultaneous-masked thresholds were measured for a 200-ms signal at 1000 Hz for a subset of conditions or taken from an earlier study. Unlike simultaneous masking, forward masking showed little effect of masker uncertainty. As confirmed by fitting a three-parameter descriptive model of forward masking, the pattern of results was similar for the sinusoidal, noise, and multicomponent forward maskers and there was no reduction in masking with decreased masker uncertainty. Performance in simultaneous masking improved to equal that in forward masking when the signal was shortened from 200 to 10 ms. Thus temporal disparities between masker and signal can offset the effects of spectral uncertainty and help separate the relative contribution of peripheral versus more central processes.
Effects of signal-to-noise ratio, signal periodicity, and degree of hearing impairment on the performance of voice-separation algorithms
Authors: Stubbs Richard J. , Summerfield Quentin
Published: October 2005

Procedures for enhancing the intelligibility of a target talker in the presence of a co-channel competing talker were evaluated in tests involving (i) continuously voiced sentences spoken on a monotone, (ii) continuously voiced sentences with time-varying intonation, and (iii) noncontinuously voiced sentences produced with natural intonation. The procedures were based on the methods of harmonic selection and cepstral filtering [R. J. Stubbs and Q. Summerfield, J. Acoust. Soc. Am. 87, 359–372 (1990)]. Target and competing voices were combined at signal-to-noise ratios (SNRs) between −10 dB and +10 dB. Subjects were a group with normal hearing and a heterogeneous group with mild-moderate cochlear hearing impairments. Processing enhanced the target voice over a range of SNRs for each type of sentence and for most listeners. Enhancement was greatest at negative SNRs. Among the impaired listeners, benefit was generally greater for those with milder losses. These results consolidate and extend previous demonstrations that voice-separation algorithms that exploit the harmonic structure of the voiced portions of speech can enhance intelligibility. However, practical application of such algorithms depends on a solution to the problem of tracking the fundamental-frequency contour of one voice in the presence of a competing voice.
Effects of absorption on the nonlinear interaction of sound beams
Authors: Darvennes Corinne M. , Hamilton Mark F. , Tjo/tta Jacqueline Naze , Tjo/tta Sigve
Published: October 2005

Nonlinearity in the propagation and interaction of sound beams in real fluids is considered, with special emphasis on the effects of absorption. Asymptotic formulas are derived for the sum and difference frequency sound generated by two harmonic sound beams. The amplitude and phase conditions of the sources are arbitrary, within the limits imposed by the parabolic approximation. A distinction is made between two main contributions to the nonlinearly generated sound in the far field, the continuously pumped sound and the scattered sound. The relative amplitudes of the pumped and scattered waves are shown to depend critically on the frequency dependence of the absorption coefficients. Numerical results are presented for the noncollinear interaction of Gaussian primary beams, and also for second harmonic generation in the field of a circular uniform piston source.
Perception of concurrent vowels: Effects of harmonic misalignment and pitch-period asynchrony
Authors: Summerfield Quentin , Assmann Peter F.
Published: October 2005

Three experiments examined the ability of listeners to identify steady-state synthetic vowel-like sounds presented concurrently in pairs to the same ear. Experiment 1 confirmed earlier reports that listeners identify the constituents of such pairs more accurately when they differ in fundamental frequency (f0) by about a half semitone or more, compared to the condition where they have the same f0. When the constituents have different f0’s, corresponding harmonics of the two vowels are misaligned in frequency and corresponding pitch periods are asynchronous in time. These differences provide cues that might aid identification. Experiments 2 and 3 determined whether listeners can use these cues, divorced from a difference in f0, to improve their accuracy of identification. Harmonic misalignment was beneficial when the constituents had an f0 of 200 Hx so that the harmonics of each constituent were well separated in frequency. Pitch-period asynchrony was beneficial when the constituents had an f0 of 50 Hz so that the onsets of the pitch periods of each constituent were well separated in time. Neither cue was beneficial when both constituents had an f0 of 100 Hz. It is unlikely, therefore, that either cue contributed to the improvement in performance found in Experiment 1 where the constituents were given different f0’s close to 100 Hz. Rather, it is argued that performance improved in Experiment 1 primarily because the two f0’s specified two pitches that could be used to segregate the contributions of each vowel in the composite waveform.
The structure of echolocation sounds used by the big brown bat Eptesicus fuscus: Some consequences for echo processing
Authors: Masters W. Mitch , Jacobs Susan C. , Simmons James A.
Published: October 2005

Analysis of the sonar emissions produced by five big brown bats (Eptesicus fuscus) during detection and range-discrimination tests show that each bat has a distinctive, “personal” emission. This may help bats distinguish their own emissions from those of others and thereby prevent jamming. Emissions usually contain three harmonics and are strongly frequency swept. Modeling of the sweep shape showed it to be more nearly linear in log time than hyperbolic (linear period modulation), which is optimal for Doppler tolerance. However, logarithmic time and linear period modulation are similar in their Doppler properties, and so bats may suffer little penalty for using a slightly nonoptimal sweep shape. We suggest that bats use logarithmic time modulation rather than linear period modulation in order to simplify signal processing during approach to prey, as this type of modulation stabilizes the filtering of echoes resulting from the bat’s automatic gain control. Likewise, the use of several harmonics in the emission may simplify signal processing of Doppler-shifted echoes by reducing the number of matched filters needed for reception.