bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of training procedures and vowel set on learning non-native vowel categories
Authors: Kingston John , Bartels Christine , Rice Jeremy , Moore Deanna , Thorburn Rachel , Benkí José , Macmillan Neil A.
Published: October 2005

Results of four new experiments are reported which examine American English listeners’ perception of German front rounded vowels. They differ from previous experiments [Kingston et al., J. Acoust. Soc. Am. 99, 2602–2603(A) (1996)] in that listeners were trained with classification of all two-stimulus subsets of four-member sets of German vowels as well as with the complete four-stimulus identification task used by Logan et al. [J. Acoust. Soc. Am. 89, 874–876 (1991)] in training. Despite the addition of these easier tasks, as in the previous experiments, both learning and generalization were modest in the four new experiments. One new experiment replicated the result obtained earlier with the front rounded vowel set, /y,Y,o/,œ/, whose members contrast for [tense] and [high]: that any contrast involving mid lax /œ/ is particularly easy. Two other experiments examined the lax front vowels contrasting for [high] and [round], /i,Y,ε,œ/; both found correlated feature contrasts to be easier than single feature contrasts, which did not differ in difficulty. The fourth experiment examined the lax round vowels contrasting for [high] and [back], /u,Y,■,œ/, and found all contrasts to be equally easy except the backness contrast between the high vowels, /u:Y/, which was markedly harder. Listeners’ accuracy on a particular contrast thus varies with the set of vowels they have heard. [Work supported by NIH and NSF.]
Native and non-native phonetic speech perception of American and Finnish listeners
Authors: Eyraud Richard , Kuhl Patricia K. , Lang A. Heikki , Iverson Paul , Fisher Ulla , Aaltonen Olli
Published: October 2005

Research by Kuhl and colleagues suggests that linguistic experience affects the internal organization of vowel and consonant categories. The present cross-language experiments test the role of language experience on the internal structure of American English and Finnish phonetic categories. Adult native listeners of Finnish and American English were tested with both native and non-native stimulus sets. The synthesized stimulus sets included a contrast that was phonemic in both languages (/r/–/l/) as well as one that was phonemic in only one language (/v/–/w/). Stimuli were modeled after native speakers of the respective language. The stimuli were: a grid of American English /r/–/l/ tokens varying in F2 and F3; a grid of Finnish /r/ tokens varying in aspiration and trill amplitude; a grid of Finnish /l/ tokens varying in F1 transition length and F2; and an American English /v/–/w/ continuum varying in F2. Listeners gave category goodness and identification judgments for individual stimuli based on their native categories, and then rated the similarity of stimulus pairs. Multidimensional scaling analyses were employed to model the internal structure of these categories. The results suggest that internal structure is dependent on language experience. [Work supported by NIH.]
Three converging tests of improvement in speech production after perceptual identification training on a non-native phonetic contrast
Authors: Bradlow Ann R. , Akahane-Yamada Reiko , Pisoni David B. , Tohkura Yoh’ichi
Published: October 2005

Previous work from these laboratories has shown that monolingual Japanese adults who were subjected to intensive perceptual identification training improved in both perception and production of English /r/-/l/ minimal pairs. The present study expanded on this finding by comparing the results from three different perceptual analysis procedures. The initial test was a direct comparison by American English listeners of the Japanese trainees’ pre-test and post-test utterances. This test assessed the extent to which AE listeners could discriminate pre-test and post-test productions. The second test used a two-alternative forced-choice identification paradigm to assess the intelligibility of the pre-test and post-test /r/–/l/ words. The final test employed an open-set transcription task in which the AE listeners simply transcribed the Japanese productions. Each of these perceptual analysis tests submitted the Japanese productions to increasingly stringent judgment criteria, and thus provided different information about the nature of the production improvement that results from perception training. The long-term effects of this learning was also examined by retesting the Japanese trainees’ production abilities 3 and 6 months after perceptual training was completed. [Work supported, in part, by NIH Grant Nos. DC-00012 and DC-00111 to Indiana Univ., Bloomington.]
Differences between native and non-native speakers’ realization of stress-related durational patterns in American English
Authors: Shibuya Yoshiho
Published: October 2005

The purpose of this study was to investigate differences between native speakers’ and non-native speakers’ realization of stress-related duration and pitch patterns in English. Anderson-Hsieh et al. [Lang. Learn. 42, 529–555 (1992)] found that prosodic deviance showed a significant negative impact on native speakers’ judgments of non-native pronunciation. Japanese uses pitch to highlight accented syllables; English uses pitch, duration, and loudness. Therefore, it is expected that Japanese speakers use pitch, when speaking English, more than American speakers, but use duration less. Experimental results confirmed this. Three Americans and three Japanese were instructed to read English sentences which included words containing six target vowels, in different stress conditions (reduced, unstressed, and stressed), sentence-medially and -finally. It was found that in American speakers’ utterances, the difference in vowel duration showed constant increase from reduced to stressed. Japanese speakers’ utterances also showed an increase, but the differences among the three stress levels were much smaller than native speakers’. The frequency of the pitch peaks showed the opposite pattern: Japanese speakers showed greater differences than the Americans. These results suggest that Japanese speakers realize English stress using the parameters for realizing pitch accent, leading to less acceptable English speech.
The acoustic structure of /i/, /u/, and /a/ in mothers’ speech to infants and adults
Authors: Andruski Jean E. , Kuhl Patricia K.
Published: October 2005

Research has shown that exposure to a specific language alters infants’ perception of vowel sounds by 6 months of age. Language spoken to infants may exert an important influence on the development of language-specific patterns of vowel perception. This study compares the acoustic structure of vowels produced by ten American mothers in conversation with their infant and another adult. In both conversations, mothers were instructed to use seven words which contained either /i/, /u/, or /a/ (‘‘bead, sheep, boot, shoe, pot, sock’’ and ‘‘top’’). Results indicate that mothers consistently increased the degree of acoustic separation between vowel categories in their speech to infants, in comparison with their speech to adults. It is speculated that the acoustic structure of vowels in motherese speech contributes to infants’ acquisition of native-language vowel categories by increasing between-category acoustic differences and by highlighting the features that distinguish these vowels. Currently an attempt is being made to confirm whether this pattern is universal in infant-directed speech with collaborators in Sweden and Russia. Preliminary results suggest that the expansion of the ‘‘acoustic envelope’’ seen in American mothers’ speech to infants holds cross-linguistically. [Work supported by the Social Sciences & Humanities Research Council of Canada and NIH.]
Re-examining age-related differences in the perception of ‘‘say/stay.’’
Authors: Nittrouer Susan , Crowther Court S.
Published: October 2005

Previous ‘‘say/stay’’ perception studies using synthetic stimuli posited F1-onset frequency and gap duration as the relevant cues. Children needed shorter gaps than adults to respond ‘‘stay’’ when F1 onset weakly indicated ‘‘stay,’’ suggesting that children weight that formant transition more. Replicating these experiments with natural speech produced unexpected findings. Acoustic analysis of natural ‘‘say’’ and ‘‘stay’’ tokens showed that: (1) F1 onset did not vary for ‘‘say’’ and ‘‘stay;’’ (2) F2/F3 onsets did vary; and (3) a burst was present in ‘‘stay.’’ Perceptual stimuli, therefore, consisted of natural, burstless vocalic portions from ‘‘say’’ and ‘‘stay,’’ and these same portions with a burst added. Each portion was combined with a natural ‘‘s’’ noise at seven gap durations. The burst effect was stronger for adults than children, and F2/F3 onset had an effect only for burstless stimuli. A second experiment was designed to examine the effects of F2/F3 in burstless stimuli, but adults failed to hear any stimuli as ‘‘stay.’’ Children had no trouble. It is concluded that: (1) F1 onset is not a cue to ‘‘say/stay;’’ (2) adults have learned to use the burst as a cue to ‘‘stay’’ identity; and (3) previous results were not due to the use of synthetic speech. [Supported by NIDCD grant R01 DC 00633.]
A cross-language comparison of speaking rate effects on the production of VOT
Authors: Magloire Joel G. , Green Kerry P.
Published: October 2005

The present study investigated the effects of linguistic experience on the production of voice onset time (VOT) in syllable-initial stop consonants. Spanish and English realize the voicing distinction using different phonetic categories. Of interest in this study was how language background influenced VOT across different speaking rates. Three groups of subjects (English and Spanish monolinguals and Spanish–English bilinguals), produced sentences containing voiced and voiceless stops at different speaking rates. Care was taken to place the bilinguals into Spanish and English monolingual modes on separate occasions. Preliminary analyses of the bilinguals’ data suggest several findings. Comparing the VOT values for bilinguals’ /p/ tokens in both language modes provided evidence for separate phonetic categories. Changes in speaking rate affected the VOT values for the voiceless tokens when in English mode and the voiced tokens when in Spanish mode. Finally, differences were found among the talkers in the way in which they realized the voicing distinction in Spanish, but not in English mode. These results point to differential effects of speaking rate on phoneme categories as a function of language mode. Additional analyses will be presented comparing productions by Spanish and English monolinguals to Spanish–English bilinguals’ in their corresponding language modes. [Work supported by NSF.]
Locating sound sources with vector sound-intensity probes, using polynomial continuation
Authors: Hickling Robert , Morgan Alexander P.
Published: October 2005

Vector sound intensity (i.e., sound-power flow per unit area) can be used to locate sound sources. In a previous paper [J. Acoust. Soc. Am. 97, 856–866 (1995)] it was shown experimentally that the direction of a source can be determined with a vector sound-intensity probe within ±2°. It was also shown that the directions of two continuous, noncoherent sources can be found with a single sound-intensity probe, using the spectral characteristics of the sources and/or spectral subtraction. In the present theoretical paper, it is demonstrated that a system of two vector probes can determine both the spatial coordinates and the sound-power output of two monopole sources through numerical solution of a set of nonlinear equations by the method of polynomial continuation. This procedure can be extended to a greater number of sources and an equal number of probes.
Response to ‘‘Comments on ‘Comparisons of vibration frequencies for rods and beams from one-dimensional and three-dimensional analyses’ ’’ [J. Acoust. Soc. Am. 100, 1890–1892 (1996)]
Authors: Leissa Arthur , So Jinyoung
Published: October 2005

The authors respond to the comments by Hutchinson.
Finite-element modeling of the normal and surgically repaired cat middle ear
Authors: Ladak Hanif M. , Funnell W. Robert J.
Published: October 2005

In this work, three-dimensional finite-element models of the normal and surgically repaired cat middle ear were developed. The normal middle-ear model was formed by adding explicit representations for the footplate and cochlear load to an existing model of the cat eardrum. The footplate was modeled as a thin plate with a thickened rim. The cochlear load was represented by springs attached along the footplate’s periphery. The model is valid for frequencies below 1 kHz and for physiological sound levels. Eardrum and manubrium displacements, and out-of-plane displacements of the footplate’s center, were found to compare well with experimental results. The normal model was modified to simulate the effects of two types of middle-ear surgery, both of which are used to repair a discontinuous ossicular chain. Bulging of the footplate was found to occur when a prosthesis made direct contact with the footplate. The location of the prosthesis along the manubrium did not affect the motion of the footplate as long as the joints were all rigid. When the joints were flexible, the largest displacements occurred when the prosthesis was positioned near the upper end of the manubrium.
Toward optimizing the clinical utility of distortion product otoacoustic emission measurements
Authors: Stover Lisa , Gorga Michael P. , Neely Stephen T. , Montoya Danielle
Published: October 2005

This study examined the effect of primary stimulus level on the ability of distortion product otoacoustic emission (DPOAE) measurements to separate normal-hearing from hearing-impaired ears. Complete I/O functions were obtained for nine f2 frequencies on 210 people approximately evenly divided between normal hearing and hearing impaired. Clinical decision theory was used to assess both DPOAE amplitudes and DPOAE threshold as diagnostic indicators of hearing status. Moderate level primary stimuli elicited responses that separated normal from impaired better than either lower level or higher level stimuli. The two populations were differentiated for all frequencies above 500 Hz by DPOAE amplitude, given primary levels, L1 and L2, of 65 and 55 dB SPL. DPOAE threshold performed equally well, but threshold ambiguity in noise and longer testing times make it a less suitable DPOAE measure to use diagnostically.
Effects of stimulus rate on the feline brain-stem auditory evoked response during development. I. Peak latencies
Authors: Burkard Robert , McGee JoAnn , Walsh Edward J.
Published: October 2005

The effects of stimulation rate on the brain-stem auditory evoked response (BAER) of developing and adult cats were investigated. Age ranged from 10-post-natal days to young adults. Clicks were presented at levels of 90 dB pSPL and 20 dB above each animal’s click threshold (20 dB SL). For all animals, a conventional BAER rate series was obtained at rates of 5, 10, 30, 60, and 90 Hz. BAERs were also obtained using pseudorandom pulse sequences called maximum length sequences (MLSs). The minimum time between pulses, the minimum pulse interval (MPI), included 0.5, 1, 2, 4, and 6 ms, which correspond to average rates of 1000, 500, 250, 125, and 83 Hz, respectively. Dependent variables included the latencies of the first four BAER peaks, labeled i through iv. MLS BAERs were indistinguishable from conventional BAERs at all ages studied. In general, for both conventional and MLS BAERs, peak latencies and the i–iv interval increased with increasing stimulus rate. Although absolute peak latencies and the i–iv interval decreased systematically with age, the relative shift in latency and i–iv interval induced by increasing stimulus rate decreased during development. The enhanced sensitivity to stimulus rate observed at younger ages was not the consequence of the threshold improvement that occurs during development since similar observations were made when stimuli were presented at a constant absolute level (90 dB pSPL) or at a constant level above threshold (20 dB SL). In addition, successive BAER peaks exhibited progressively larger latency shifts with increasing stimulus rate at all ages studied. These data suggest that higher stimulus rates produce greater neural adaptation resulting in prolonged BAER peak latencies. Furthermore, the effects of adaptation are cumulative across synapses, and the mechanisms responsible for the acquisition of adult-like adaptation properties develop during the early post-natal period in the cat.
A three accelerometer method for the measurement of flow rate in pipe
Authors: Kim Young-Key , Kim Yang-Hann
Published: October 2005

A method for the measurement of flow rate in a pipe is proposed. The method utilizes the vibration signals that are generated using an external excitor. Three accelerometers on the surface of a pipe are used to measure these signals. Applying wave decomposition theory to the measured vibration signal, change of wave number, which is one of the results caused by flow rate change, is estimated. The change of wave number is converted into flow rate using the simple mathematical model of fluid conveying pipe. The main advantage of this method is that it does not require any sensory system inside the pipe, so that the characteristics of flow are not disturbed and the measurement position can be easily moved. All possible errors associated with the proposed measurement system are investigated. Those are due to sensor spacing, relative position of sensor with respect to boundaries, phase mismatch as well as magnitude mismatch between sensors, and measurement noise. To verify the potential of this method, experiments using water conveying steel pipe are accomplished. Finally, the estimated flow rates are within 12% error bounds.
Ocean acoustic tomography based on peak arrivals
Authors: Skarsoulis E. K. , Athanassoulis G. A. , Send U.
Published: October 2005

The recently introduced notion of peak arrivals [Athanassoulis and Skarsoulis, J. Acoust. Soc. Am. 97, 3575–3588 (1995)], defined as the significant local maxima of the arrival pattern, is studied here as a modeling basis for performing ocean tomography. Peak arrivals constitute direct theoretical counterparts of experimentally observed peaks, and offer a complete modeling of experimental observables, even in cases where ray or modal arrivals cannot be resolved. The coefficients of the resulting peak-inversion system, relating travel-time with sound-speed perturbations, are explicitly calculated in the case of range-independent environments using normal-mode theory. To apply the peak-inversion scheme to tomography the peak identification and tracking problem is examined from a statistical viewpoint; maximum-likelihood and least-square solutions are derived and discussed. The particular approach adopted treats the identification and tracking problem in close relation to the inversion procedure; all possibilities of associating observed peaks with background arrivals are examined via trial inversions, and the best peak identification is selected with respect to a least-square criterion. The feasibility of peak tomography is subsequently demonstrated using first synthetic data and then measured data from the THETIS-I experiment. In the synthetic case the performance of the overall scheme is found to be satisfactory both with noise-free and noisy data. Furthermore, the identification, tracking, and inversion results using experimental acoustic data from THETIS-I are in good agreement with independent field observations.
Some effects of orchestra shells
Authors: Bradley J. S.
Published: October 2005

This paper presents room acoustic measurements of the effects of adding or modifying an orchestra shell in several halls. The average effects, at audience seats, of adding an orchestra shell in three large multipurpose halls were small but within predicted ranges. At mid- and high frequencies, partial shells produced intermediate results. However, at lower frequencies more complex effects were observed, because the addition of an orchestra shell modified the grazing incidence seat dip attenuation. These effects depended on the geometry of the shell and on the receiver position in the hall. On-stage measurements of support were increased by approximately 5 dB with the addition of an orchestra shell. Although orchestra shells had much larger effects on-stage, they were also found to produce significant audible effects at audience seats.
A parametric study of the concentric-ring transducer design for MRI guided ultrasound surgery
Authors: Fjield Todd , Fan Xiaobing , Hynynen Kullervo
Published: October 2005

Noninvasive surgery using high-powered, focused ultrasound transducers in conjunction with magnetic resonance imaging has been shown to be feasible in previous studies. For clinical treatments, the geometry of standard MRI equipment limits the space available for ultrasound surgical equipment. This space requirement can be reduced in one dimension by using phased arrays to control the focal depth, thus eliminating the space required for the motion of a fixed focus transducer. Because of its symmetry, an annular array is ideal for changing the focal depth. Previous works have simulated, built, and characterized various concentric-ring transducers; however, no study has thoroughly examined the potential and limitations of the concentric-ring design for MRI guided ultrasound surgery. The present work is a systematic examination of the capabilities of the concentric-ring array, using numerical simulations to predict the power field, temperature distribution, and accumulated thermal dose. The results presented here illustrate the effects of ring size, center-to-center spacing configurations, number of rings, and radius of curvature on transducer performance. A 10-cm radius of curvature transducer with 14 evenly spaced rings has been built and characterized in order to verify the accuracy of the numerical simulations. The pressure-squared fields produced by this transducer are in excellent agreement with the simulated fields.
A computer model of blues music and its evaluation
Authors: Hall Mark A. , Smith Lloyd
Published: October 2005

This paper describes a new algorithm that composes blues melodies to fit a given chord sequence. It comprises an analysis stage followed by a synthesis stage. The analysis stage produces a Markov model composed of zero, first-, and second-order transition tables covering both pitches and rhythms. In order to capture the relationship between harmony and melody, a set of transition tables is produced for each chord in the analyzed songs. The synthesis stage uses the output tables from analysis to generate new melodies; second-order tables are used as much as possible, with fall back procedures to lower-order tables. Some constraints are encoded in the form of rules to control the placement of rhythmic patterns within measures, pitch values for long duration notes and pitch values for the start of new phrases. The model was evaluated by a listening experiment; results showed that listeners were unable to reliably distinguish human from computer composed melodies.
Design and tone in the mechanoacoustic piano. Part II. Piano structure
Authors: Conklin Harold A.
Published: October 2005

Editorial note: This invited and tutorial article is being published in three parts. The abstract for the series was published in Part I—Piano hammers and tonal effects [J. Acoust. Soc. Am. 99, 3286–3296 (1996)].
A simple calculation approach for the second harmonic sound field generated by an arbitrary axial-symmetric source
Authors: Ding Desheng , Shui Yongan , Lin Jingbo , Zhang De
Published: October 2005

In a linear approximation, an arbitrary axial-symmetric source can be expressed as the linear superposition of a set of Gaussian sources and the corresponding radiated sound field can be represented as the superposition of this set of Gaussian beams. The analysis is extended to the second harmonic generation due to nonlinear effects under a quasilinear approximation, then the second harmonic sound field could be considered as a sum of self- and cross-interaction terms produced by a series of Gaussian beams. Therefore, the calculation of the second harmonic sound field of an axial-symmetric source can be reduced to a simple linear combination of a set of exponential integral functions, instead of a complicated triple integral. In order to verify this calculation approach, the second harmonic generation of a focused and a simple piston source is examined, and the result is in good agreement with that in earlier paper by complicated computation.
The effect of saturated transmission scintillation on ocean acoustic intensity measurements
Authors: Makris Nicholas C.
Published: October 2005

Coherence theory is used to analyze the statistical properties of ocean-acoustic intensity fluctuations measured after saturated multipath propagation. Previous analyses in this area have been implicitly limited to certain special cases for which the time-bandwidth product of the field received from a given source is unity. In this paper, the statistical description is extended and generalized to be a function of measurement time and temporal coherence. As a result, the well known 5.6-dB transmission loss (TL) standard deviation of Dyer is found to be a special case of a more general TL standard deviation that approximates 4.34 sqrt(1/μ) dB when the time-bandwidth product μ is large. Therefore, the TL standard deviation approaches zero for increasing μ, as it must in the deterministic limit of an arbitrarily large sample size. A similar generalization is obtained for the TL mean, from which it is found that the sonar equation must be corrected for a μ-dependent bias that vanishes in the deterministic limit of large μ. Additionally, asymptotic analysis shows that intensity statistics in the saturated region converge to a log-normal distribution, where μ≳4 is typically sufficient for the log-normal approximation to be made.
Broadband acoustic transmission intensity fluctuations in the Tyrrhenian Sea
Authors: Uscinski B. J. , Akal T.
Published: October 2005

An acoustic propagation experiment was carried out in the Tyrrhenian Sea in October 1985 in which signals from a broadband source were recorded at a range of 5 km with a vertical 62-m hydrophone array over a period of 5 days. The experiment, named ‘‘NAPOLI 85,’’ was designed to investigate the transfer function of the ocean medium over an acoustic frequency range from 250–2000 Hz as a function of time and position down the vertical array. This paper treats the ocean transfer function in both the time and frequency domains for the lower refracted path. The intensity fluctuations down the array at an acoustic frequency of 1 kHz are presented for the 5 days. Large fluctuations occur simultaneously over the whole extent of the array, and these can be explained by refractive effects in an intrusive layer. There are also weak spatial variations down the array arising from diffractive effects in the layer. The physical mechanisms causing the time variations in the layer are not yet understood.
Two-dimensional angle of arrival fluctuations
Authors: Di Iorio Daniela , Farmer David M.
Published: October 2005

Angle of arrival fluctuations are one manifestation of acoustic propagation through a turbulent flow. Here the two-dimensional angle of arrival distribution for a 670-m acoustic path through a high Reynolds number flow in a tidal channel is examined and its origin and relationship to the flow field is determined. Over scales greater than the variability due to turbulence, a solution of the ray propagation equation explains the effect of advection on the horizontal arrival angle. The rapidly fluctuating two-dimensional angle of arrival distribution shows a degree of scatter consistent with the level of turbulent intensity. After removal of effects due to the finite aperture, orthogonal components are correlated during strongly sheared flow implying that the turbulence is weakly anisotropic over the measured scales. This anisotropy is discussed in terms of the cross stream velocity gradients ∂v/∂x′ and ∂v/∂z′, where (x′,z′) are perpendicular diagonal coordinates.
Viscous attenuation of sound in dilute suspensions of rigid particles
Authors: Temkin S.
Published: October 2005

This work considers the attenuation of sound for plane waves traveling in isothermal suspensions of rigid particles, in the limit of small volume concentrations. Two new results for the viscous attenuation coefficient are presented. The first is based on the complete force equation for a sphere in an oscillating, incompressible fluid, and leads to a low-frequency attenuation which differs from existing results, except when the fluid-particle density ratio is small, as is the case in aerosols. The second result is based on an earlier study [S. Temkin and C. M. Leung, J. Sound Vib. 49, 75–92 (1976)] which considered the motion of a sphere in a sound wave in a viscous fluid. This second result includes compressibility effects and merges with the first at low frequencies and with the equivalent result due to scattering alone at high frequencies.
Factors which determine the tunable frequency range of tunable transducers
Authors: Alwi Hasan A. B. , Smith Brian V. , Carey John R.
Published: October 2005

Tuning or varying the resonance frequency of a transducer by adding an additional layer of ceramic, called the control ceramic, is a method for designing a wide bandwidth transducer. By loading the control ceramic with an inductive electrical load the resonance frequency of the whole structure is variable or tunable over a wide range of frequency. Two designs of tunable transducer are discussed in this paper; a two-plate thickness-driven structure with a fundamental frequency of 240 kHz and a sandwich structure with a fundamental frequency of 30 kHz. Tunable ranges of 1.5 and 1.8 oct are obtained, respectively. It is established that the limit of the tunable range for the two-plate transducer is between the fundamental harmonic and the second overtone of the whole structure, which are defined with the control ceramic short circuited. For the sandwich transducer the tunable range is between the fundamental harmonic and the first overtone of the whole structure, which are defined when the control ceramic short circuited. An analysis based on the Mason transmission-line model shows that the fundamental limit of the tunable range is determined by the fundamental resonance frequency and the dynamic coupling coefficient of the drive ceramic and is affected by the presence of any bonds and shims between the ceramics. To obtain a continuously tunable frequency range the position of the drive ceramic must be between the radiating front-end of the structure and the control ceramic.
Simulation of fixed microphone arrays for directional hearing aids
Authors: Liu Chen , Sideman Samuel
Published: October 2005

Microphone arrays with fixed optimum weights are known to suppress the background noise and reverberation that severely reduce the effectiveness of conventional hearing aids. By means of a general technique for digital frequency-domain implementation of optimum broadband arrays that was developed recently [C. Liu and S. Sideman, J. Acoust. Soc. Am. 98, 241–247 (1995)], a practically promising system is proposed to realize the arrays with the well-known sensitivity-constrained superdirective beamforming weights, and with five identical omnidirectional, cardioid, hypercardioid, or dipole microphones, respectively, in the endfire or broadside configurations, which were theoretically proposed by Stadler and Rabinowitz [J. Acoust. Soc. Am. 94, 1332–1342 (1993)]. The digital broadband frequency-domain beamforming system allows the broadband superdirective beamforming weights to be faithfully and independently applied to each frequency component of the signal. The practical application of this technique is demonstrated through computer simulation of the system in anechoic situations. Furthermore, its performance in simulated reverberant environments is evaluated.
Reduction to parts: A semianalytical approach to the structural acoustics of a cylindrical shell with hemispherical endcaps
Authors: Utschig M. , Achenbach J. D. , Igusa T.
Published: October 2005

A reduction-to-parts (RTP) method has been developed to approximate the acoustic impedance of a cylindrical shell with hemispherical endcaps. The approximation greatly reduces the computational effort required to calculate the acoustic impedance as compared to discretization methods and a variational formulation. The shell is subdivided into three parts, two hemispheres and a finite-length cylinder, which can be considered as subregions of separable geometric shapes. Surface displacements from the original shell are applied to these separable geometries, and the corresponding calculated surface pressure responses are mapped back to the original shell. An approximation to the acoustic impedance of the original shell is calculated using the prescribed displacements and the mapped surface pressures. The accuracy of the approximation is improved in the low-frequency range when pressure generated on neighboring parts is taken into account. To verify the approximation, the surface and far-field responses due to a point load are compared with the responses calculated using a variational formulation. The RTP method accurately predicts the near- and far-field acoustic pressures.
Effects of a porous jacket on sound radiated from a pipe
Authors: Kanapathipillai S. , Byrne K. P.
Published: October 2005

Conventional pipe laggings incorporate a porous jacket and an impervious outer cladding sheet. It has been observed during investigations of such pipe laggings that a simple porous jacket applied by itself to a pipe can actually increase the sound radiated. Reasons for this phenomenon are discussed. The effect of a rigid frame porous jacket around a pipe is examined theoretically for the breathing, bending, and ovalling modes of pipe vibration. The predicted insertion loss associated with the bending mode of pipe vibration is compared with the corresponding experimental result and some of the results of a parametric study are given.
Room acoustic prediction based on a unified treatment of diffuse and specular reflection
Authors: Dalenbäck Bengt-Inge L.
Published: October 2005

A new general algorithm for room acoustic prediction is presented. The algorithm, based on approximate cone tracing, handles diffuse reflection by a splitup of cones incident on diffusing surfaces. The splitup of cones treats the interaction between specular and diffuse reflection in a physically sensible manner. A ‘‘brute-force’’ implementation of such an algorithm inevitably creates an exponential dependence of the calculation time on the number of reflection combinations between diffusely reflecting surfaces, and therefore results in extremely long processing times. By exploiting the properties of diffuse reflection, the described algorithm displays an essentially linear dependence resulting in processing times short enough also for personal computers. The algorithm adapts its behavior to the properties of each specific environment, relies on very few nonverifiable assumptions, and is designed to meet the specific requirements of auralization. The splitup of cones creates a myriad of weak diffuse reflections resulting in a very smooth late decay. The algorithm is described in detail and sample predictions are shown.
Identifying cross-correlation peaks due to multipaths with application to optimal passive localization of transient signals and tomographic mapping of the environment
Authors: Spiesberger John L.
Published: October 2005

Cross-correlating the output of two widely separated receivers may fail to provide a means to estimate the arrival time difference of the first arriving signals when the cross-correlation of accompanying multipaths have amplitudes that may be confused with that between the first arrivals. Based on information in two auto-correlation functions, a new, robust, and efficient method is described for identifying which peak in the cross-correlation function corresponds to the arrival time difference between the first arrivals. The information in auto-correlation functions is often sufficient to identify the relative arrival times of all the multipaths at each receiver. The technique relies on (1) a high signal-to-noise ratio following auto- and cross-correlation, and (2) time series which have been preprocessed to suppress all signals except those emanating from a single source. The technique works even when (1) the number of multipaths is unknown, (2) the received signal is not visible above the noise, (3) the transmission time is unknown, (4) the transmitted waveform is unknown, (5) the spatial coordinates of the multipaths are unknown or are impractical to estimate, and (6) the differential Doppler between multipaths is not too large. These techniques may be useful for localizing transient signals and mapping the environment with tomography.
On the incorporation of moiré shape measurements in finite-element models of the cat eardrum
Authors: Funnell W. Robert J. , Decraemer Willem F.
Published: October 2005

The mechanical behavior of the eardrum has previously been shown to depend critically on its shape, but accurate shape measurements have been difficult to make. Phase-shift moiré topography provides a valuable technique for measuring such shapes, and measurement in the presence of large static pressures facilitates the determination of the boundaries of the pars tensa, pars flaccida, and manubrium. New measurements of the shape of the cat eardrum are presented. The presence of hysteresis in the pressure-displacement response is demonstrated. The shapes are incorporated in individualized finite-element models for four different ears, and the variability between and within animals is examined. Fixed-manubrium low-frequency displacements are simulated and compared for the different models.
Speech compensation to structural modifications of the oral cavity
Authors: McFarland David H. , Baum Shari R. , Chabot Caroline
Published: October 2005

Acoustic and perceptual analyses of vowels, stops, and fricatives produced with and without an artificial palate were conducted. Recordings were made both immediately upon insertion of the palate and following a 15-min adaptation period. Results of the acoustic analyses revealed significant alterations in the fricative spectra under conditions of perturbation with fewer, if any, changes in the vowels and stop consonants. Perceptual data confirmed these patterns and provided evidence of possible improvements in compensation over time. The data are compared to our previous studies of speech sound articulation under bite-block conditions. Differences between adaptation to modifications of oral structure (artificial palate) and oral function (jaw fixation by a bite block) are considered.
On the relation between comodulation masking release and temporal modulation transfer functions
Authors: Berg Bruce G.
Published: October 2005

Explanations for the phenomenon known as comodulation masking release (CMR) generally assume that temporal envelope information from different peripheral filters is compared, thus entailing multiple envelope representations. Here it is shown that a leaky-integrator model, yielding a single envelope representation extracted from a broad frequency range, provides an alternative account of CMR. One prediction obtained from model simulations is that adding a single tone to the stimulus will disrupt the CMR effect, leading to an increase in thresholds. Supporting evidence from several experiments shows that the magnitude of CMR is reduced following the addition of a single tone, even when separated from comodulated masking and flanking bands by more than an octave. Whereas these findings are consistent with the leaky-integrator model, they cannot be easily explained by models which assume multiple envelope representations.
Development of auditory information integration abilities
Authors: Allen Prudence , Nelles James
Published: October 2005

The ability of normal-hearing children (aged 4 through 7 years) and adults to integrate information was measured in an auditory sample discrimination task. On each trial a pair of tonal sequences was played whose component frequencies were randomly drawn from two equal-variance, Gaussian distributions with different means. The listeners task was to identify the sequence drawn from the distribution with the higher mean frequency. Performance was first evaluated as a function of the number of components in each sequence. Results showed that discrimination accuracy improved with increasing age until age 7, at which time performance was adult-like. The 7-year-olds and the adults discriminated the sequences with increasing accuracy as the sequence length was increased, but the 4- to 6-year-old listeners, as a group, did not. Data were fitted with a model with two free parameters, one representing resolution of the components and presumed to reflect peripheral processing, and another representing central noise added to the decision process after the component information is combined [R. Lutfi, J. Acoust. Soc. Am. 86, 934–944 (1989)]. On average, both parameters showed gradual changes as age increased, with adult-like values by 7 years of age. Individual data however suggest that the changes in central noise with age may be less gradual than the changes in peripheral resolution. In a second condition, increases in component duration produced improved performance for the 7-year-olds and the adults, while that of the younger listeners remained the same. Fitted parameters suggested improvements in component resolution for the older children, with no changes in central noise levels. In a third condition, reducing the overlap in the distributions improved performance for only a few of several younger children. This improvement was attributable to lower levels of central noise. Overall, these results suggest that with increasing age children are better able to discriminate between sounds that are variable and have overlapping acoustic characteristics. This age-related improvement may be attributed both to improvements in the ability to resolve the components and to reductions in central noise.
The perceptual magnet effect as an emergent property of neural map formation
Authors: Guenther Frank H. , Gjaja Marin N.
Published: October 2005

The perceptual magnet effect is one of the earliest known language-specific phenomena arising in infant speech development. The effect is characterized by a warping of perceptual space near phonemic category centers. Previous explanations have been formulated within the theoretical framework of cognitive psychology. The model proposed in this paper builds on research from both psychology and neuroscience in working toward a more complete account of the effect. The model embodies two principal hypotheses supported by considerable experimental and theoretical research from the neuroscience literature: (1) sensory experience guides language-specific development of an auditory neural map, and (2) a population vector can predict psychological phenomena based on map cell activities. These hypotheses are realized in a self-organizing neural network model. The magnet effect arises in the model from language-specific nonuniformities in the distribution of map cell firing preferences. Numerical simulations verify that the model captures the known general characteristics of the magnet effect and provides accurate fits to specific psychophysical data.
Prominence lent by rising and falling pitch movements: Testing two models
Authors: Rump H. H. , Hermes Dik J.
Published: October 2005

Two experiments are reported in which a pitch-level difference (PLD) model for prominence perception [Hermes and Rump, J. Acoust. Soc. Am. 96, 83–92 (1994)] is subjected to further tests. The model holds that the contribution of pitch to the perceived degree of prominence is proportional to the difference in pitch level between the vocalic nuclei of the accented and the previous syllable. In experiment I, the influence of stretching and compressing the utterance in time was assessed. It was found that the predictions made by the model were not fully supported by the data. An alternative model was developed according to which pitch movements resynthesized in the same register lend equal prominence when pitch levels on the upper declination lines in the stimuli are equal. These two models gave different predictions when the lower declination lines are different. This was tested in experiment II. The results which are more or less between the predictions by the two models suggest that low pitch levels play a smaller role in prominence perception than high pitch levels do.
Auditory and visual speech perception: Confirmation of a modality-independent source of individual differences in speech recognition
Authors: Watson Charles S. , Qiu William Weiguang , Chamberlain Mary M. , Li Xiaofeng
Published: October 2005

Two experiments were run to determine whether individual differences in auditory speech-recognition abilities are significantly correlated with those for speech reading (lipreading), employing a total sample of 90 normal-hearing college students. Tests included single words and sentences, recorded on a videodisc by a male speaker [Bernstein and Eberhardt, Johns Hopkins Lipreading Corpus, The Johns Hopkins University, Baltimore, MD, 1986]. The auditory speech was presented with a white noise masker, at −7 dB Sp/N. The correlations between overall auditory and visual performance were 0.52 and 0.43 in the two experiments, consistent with the existence of a modality-independent ability to perceive linguistic ‘‘wholes’’ on the basis of linguistic fragments. Subjects in the second experiment also identified printed sentences, with 40%–60% portions of the printed characters deleted. Performance on this graphical ‘‘fragmented-sentences test’’ also correlated significantly with auditory speech recognition, providing a possible clue to the cognitive basis for the look-versus-listen correlation. The existence of a modality-independent source of variance in speech-recognition abilities may be a partial explanation of the difficulty in demonstrating strong associations between psychoacoustic measures of spectral or temporal acuity, and speech discrimination or identification. Female subjects in both experiments were significantly better lipreaders than their male counterparts.