Volume 137, Issue 1, January 2015
- jasa express letters
- animal bioacoustics
- architectural acoustics
- biomedical acoustics
- musical acoustics
- physical acoustics
- psychological and physiological acoustics
- speech communication
- structural acoustics and vibration
- underwater acoustics
- letters to the editor
- acoustical news
- acoustical standards news
- book reviews
- reviews of acoustical patents
Index of content:
- JASA EXPRESS LETTERS
137(2015); http://dx.doi.org/10.1121/1.4902434View Description Hide Description
Dispersion curves characterize many propagation mediums. When known, many methods use these curves to analyze waves. Yet, in many scenarios, their exact values are unknown due to material and environmental uncertainty. This paper presents a fast implementation of sparse wavenumber analysis, a method for recovering dispersion curves from data. This approach, based on orthogonal matching pursuit, is compared with a prior implementation, based on basis pursuit denoising. In the results, orthogonal matching pursuit provides two to three orders of magnitude improvement in speed and a small average reduction in prediction capability. The analysis is demonstrated across multiple scenarios and parameters.
A numerically stable formulation of the Green's function parabolic equation: Subtracting the surface-wave pole137(2015); http://dx.doi.org/10.1121/1.4902423View Description Hide Description
The original formulation of the Green's function parabolic equation (GFPE) can have numerical accuracy problems for large normalized surface impedances. To solve the accuracy problem, an improved form of the GFPE has been developed. The improved GFPE formulation is similar to the original formulation, but it has the surface-wave pole “subtracted.” The improved GFPE is shown to be accurate for surface impedances varying over 2 orders of magnitude, with the largest having a magnitude exceeding 1000. Also, the improved formulation is slightly faster than the original formulation because the surface-wave component does not have to be computed separately.
High-frequency whistles of Guiana dolphins (Sotalia guianensis) in Guanabara Bay, southeastern Brazil137(2015); http://dx.doi.org/10.1121/1.4902428View Description Hide Description
Guiana dolphins produce whistles with a higher frequency and less complexity than most other delphinid species. The present study used a recording system with sampling rate of 192 kHz to describe the high-frequency whistles of Sotalia guianensis in Guanabara Bay, Rio de Janeiro. Eleven acoustic parameters (start, end, minimum, maximum, delta, center and peak frequency, duration, and frequency at , , and of duration) were measured for all whistles. Whistles with a fundamental frequency up to 66.7 kHz were reported, thereby expanding the known frequency range of this species.
137(2015); http://dx.doi.org/10.1121/1.4903228View Description Hide Description
The optimal integration of information from independent Poisson sources (such as neurons) was analyzed in the context of a two-interval, forced-choice detection task. When the mean count of the Poisson distribution is above 1, the benefit of integration is closely approximated by the predictions based on the square-root law of the Gaussian model. When the mean count falls far below 1, however, the benefit of integration clearly exceeds the predictions based on the square-root law.
137(2015); http://dx.doi.org/10.1121/1.4902425View Description Hide Description
There are two competing national standards for the calculation of loudness of steady sounds, DIN 45631 and ANSI S3.4. Their different concepts of critical bands lead to different predictions for broadband sounds. As that discrepancy is neither constant nor linear but highly frequency-dependent, the present study investigates spectral loudness summation in three frequency regions, at various levels, and using two different methods. The results show that both algorithms overestimate loudness; however, DIN 45631 comes closer to the subjective evaluations and often falls within their interquartile range. The overestimation by the standards is particularly large in the frequency range from 2 to 5 kHz.
Laboratory measurements of high-frequency, acoustic broadband backscattering from sea ice and crude oil137(2015); http://dx.doi.org/10.1121/1.4902421View Description Hide Description
Recent decreases in summer sea ice cover are spurring interest in hydrocarbon extraction and shipping in Arctic waters, increasing the risk of an oil spill in ice covered waters. With advances in unmanned vehicle operation, there is an interest in identifying techniques for remote, underwater detection of oil spills from below. High-frequency (200–565 kHz), broadband acoustic scattering data demonstrate that oil can be detected and quantified under laboratory grown sea ice and may be of use in natural settings. A simple scattering model based on the reflection coefficients from the interfaces agrees well with the data.
137(2015); http://dx.doi.org/10.1121/1.4902420View Description Hide Description
This letter presents a simple and practical method for evaluating the sound field radiated from a waveguide. By using the proposed method, detailed information about the radiated sound field can be obtained by measuring the sound field in the mouth of the baffled waveguide. To examine this method's effectiveness, the radiated sound pressure distribution in space was first evaluated by using the proposed method, and then it was measured directly for comparison. Experiments using two different waveguides showed good agreement between the evaluated and the measured radiated sound pressure distributions.
137(2015); http://dx.doi.org/10.1121/1.4903916View Description Hide Description
Enhancement of the perceptual encoding of talker characteristics (indexical information) in speech can facilitate listeners' recognition of linguistic content. The present study explored this indexical-linguistic relationship in nonnative speech processing by examining listeners' performance on two tasks: nonnative accent categorization and nonnative speech-in-noise recognition. Results indicated substantial variability across listeners in their performance on both the accent categorization and nonnative speech recognition tasks. Moreover, listeners' accent categorization performance correlated with their nonnative speech-in-noise recognition performance. These results suggest that having more robust indexical representations for nonnative accents may allow listeners to more accurately recognize the linguistic content of nonnative speech.
137(2015); http://dx.doi.org/10.1121/1.4903914View Description Hide Description
Monaural envelope correlation perception is the ability to discriminate between stimuli composed of two or more bands of noise based on envelope correlation. Sensitivity decreases as stimulus bandwidth is reduced below 100 Hz. The present study manipulated stimulus bandwidth (25–100 Hz) and duration (25–800 ms) to evaluate whether performance of highly trained listeners is limited by the number of inherent modulation periods in each presentation. Stimuli were two bands of noise, separated by a 500-Hz gap centered on 2250 Hz. Performance improved reliably with increasing numbers of envelope modulation periods, although there were substantial individual differences.
137(2015); http://dx.doi.org/10.1121/1.4903919View Description Hide Description
The aim of this letter is to address a little understood question in sound source localization: Can the distance of a near sound source affect our own perception of its elevation? The issue is studied by means of an objective analysis of a database of distance-dependent head-related transfer functions (HRTFs) of a KEMAR (Knowles Electronic Manikin for Acoustic Research) mannequin with different pinnae on a dense spatial grid. Iso-directional HRTFs are compared through spectral error metrics; results indicate significant distance-dependent HRTF modifications due to the pinna occur when the source is close to the interaural axis.
137(2015); http://dx.doi.org/10.1121/1.4903917View Description Hide Description
Speech perception studies generally focus on the acoustic information present in the frequency regions below 6 kHz. Recent evidence suggests that there is perceptually relevant information in the higher frequencies, including information affecting speech intelligibility. This experiment examined whether listeners are able to accurately identify a subset of vowels and consonants in CV-context when only high-frequency (above 5 kHz) acoustic information is available (through high-pass filtering and masking of lower frequency energy). The findings reveal that listeners are capable of extracting information from these higher frequency regions to accurately identify certain consonants and vowels.
137(2015); http://dx.doi.org/10.1121/1.4903921View Description Hide Description
Although auditory brainstem responses (ABRs), the sound-evoked brain activity in response to transient sounds, are routinely measured in humans and animals there are often differences in ABR waveform morphology across studies. One possible reason may be the method of stimulus calibration. To explore this hypothesis, click-evoked ABRs were measured from seven ears in four Mongolian gerbils (Meriones unguiculatus) using three common spectrum calibration strategies: Minimum phase filter, linear phase filter, and no filter. The results show significantly higher ABR amplitude and signal-to-noise ratio, and better waveform resolution with the minimum phase filtered click than with the other strategies.
137(2015); http://dx.doi.org/10.1121/1.4903915View Description Hide Description
This study presents the first reported measurements of stimulus frequency emissions (SFOAEs) in 15 human newborns and compares their magnitudes and phase-gradient delays to those reported in adults. SFOAEs in newborns were measured at stimulus levels as low as 15 dB sound pressure level (SPL). Responses were compared between adults and newborns at stimulus levels where SFOAEs in both age groups demonstrated approximately linear growth (<40 dB SPL for newborns, <25 dB SPL for adults). Neonates had adult-like SFOAE delays when compared in this fashion, which compensates for newborn middle ear inefficiencies.
Method for generating realistic sound stimuli with given characteristics by controlled combination of audio recordings137(2015); http://dx.doi.org/10.1121/1.4904011View Description Hide Description
Audio recordings are often used to improve ecological validity of stimuli for laboratory research on effects of noise. In this paper a method is proposed for composing realistic environmental sound stimuli with (1) specified overall spectrum and (2) specified statistical distribution of sound event durations and semantic categories. The combination is addressed as a mixed integer linear programming problem. Objective measurements, for eight stimuli and a moderate-size database, validate the method. The mean error in octave bands exposure level is 2.6 dB and the statistical distribution of sound event durations and semantic categories is perfectly matched.
Overnight consolidation promotes generalization across talkers in the identification of nonnative speech sounds137(2015); http://dx.doi.org/10.1121/1.4903918View Description Hide Description
This investigation explored the generalization of phonetic learning across talkers following training on a nonnative (Hindi dental and retroflex) contrast. Participants were trained in two groups, either in the morning or in the evening. Discrimination and identification performance was assessed in the trained talker and an untrained talker three times over 24 h following training. Results suggest that overnight consolidation promotes generalization across talkers in identification, but not necessarily discrimination, of nonnative speech sounds.
137(2015); http://dx.doi.org/10.1121/1.4903920View Description Hide Description
The goal of this work was to show that a non-absorbing free plate model can predict with a reasonable accuracy guided modes measured in bone-mimicking phantoms that have circular cross-section. Experiments were carried out on uncoated and coated phantoms using a clinical axial transmission setup. Adjustment of the plate model to the experimental data yielded estimates for the waveguide characteristics (thickness, bulk wave velocities). Fair agreement was achieved over a frequency range of 0.4 to 1.6 MHz. A lower accuracy observed for the thinnest bone-mimicking phantoms was caused by limitations in the wave number measurements rather than by the model itself.
137(2015); http://dx.doi.org/10.1121/1.4904914View Description Hide Description
The present study aims to investigate the propagation of time-reversed Lamb waves in bovine cortical bone in vitro. The time-reversed Lamb waves were successfully launched at 200 kHz in 18 bovine tibiae through a time reversal process of Lamb waves. The group velocities of the time-reversed Lamb waves in the bovine tibiae were measured using the axial transmission technique. They showed a significant correlation with the cortical thickness and tended to follow the theoretical group velocity of the lowest order antisymmetrical Lamb wave fairly well, consistent with the behavior of the slow guided wave in long cortical bones.
137(2015); http://dx.doi.org/10.1121/1.4904915View Description Hide Description
Vertical-axis wind turbines are wind-energy generators suitable for use in urban environments. Their associated noise thus needs to be characterized and understood. As a first step, this work investigates the relative importance of harmonic and broadband contributions via model-scale wind-tunnel experiments. Cross-spectra from a pair of flush-mounted wall microphones exhibit both components, but further analysis shows that the broadband dominates at frequencies corresponding to the audible range in full-scale operation. This observation has detrimental implications for noise-prediction reliability and hence also for acoustic design optimization.
137(2015); http://dx.doi.org/10.1121/1.4904916View Description Hide Description
This study reports a finding about vocal expressions of emotion in Mandarin Chinese. Production and perception experiments used the same tone and mixed tone sequences to test whether pitch variation is restricted due to the presence of lexical tones. Results showed that the restriction of pitch variation occurred in all high level tone sequences (tone 1 group) with the expression of happiness but did not happen for other dynamic tone groups. However, perception analysis revealed that all the emotions in every tone group received high identification rates; this indicates that listeners used other cues for encoding happiness in the tone 1 group. This study demonstrates that the restriction of pitch variation does not affect the perception of vocal emotions.
Single-channel blind separation using L 1-sparse complex non-negative matrix factorization for acoustic signals137(2015); http://dx.doi.org/10.1121/1.4903913View Description Hide Description
An innovative method of single-channel blind source separation is proposed. The proposed method is a complex-valued non-negative matrix factorization with probabilistically optimal L 1-norm sparsity. This preserves the phase information of the source signals and enforces the inherent structures of the temporal codes to be optimally sparse, thus resulting in more meaningful parts factorization. An efficient algorithm with closed-form expression to compute the parameters of the model including the sparsity has been developed. Real-time acoustic mixtures recorded from a single-channel are used to verify the effectiveness of the proposed method.