Journal of the Acoustical Society of America最新文献

This study (1) characterized the effects of channel interaction using spectral blurring, (2) evaluated an image-guided electrode selection (IGES) method aiming to reduce channel interaction, and (3) investigated the impact of electrode placement factors on the change in performance by condition. Twelve adult MED-EL (Innsbruck, Austria) cochlear implant recipients participated. Performance was compared across six conditions: baseline (no blurring), all blurred, apical blurred, middle blurred, basal blurred, and IGES. Electrode placement information was calculated from post-insertion computerized tomography (CT) imaging. Each condition tested measures of speech recognition and subjective ratings. Results showed poorer performance when spectral blurring was applied to all channels compared to baseline, suggesting an increase in channel interaction was achieved. Vowel recognition was more sensitive to apical and middle blurring while consonant recognition was more sensitive to basal blurring, indicating that phoneme identification may be useful for assessing channel interaction clinically. IGES did not significantly improve group performance, and electrode placement factors did not impact results. However, participants who were more affected by spectral blurring tended to benefit more from IGES. These findings indicate that spectral blurring can help identify areas most affected by channel interaction to help optimize electrode selection.

An acoustic propagation experiment was conducted in the western continental shelf of India (off Kollam, Kerala) in water depth of ∼71 m with seafloor consisting of hard sandy sediments. The multipath arrival times are obtained from peaks in acoustic impulse response measurements made on a single hydrophone for two source-receiver ranges of 245 m and 320 m. The arrival times are used for inverting the water column sound speed profile (SSP) utilizing the empirical orthogonal functions (EOFs), which can completely describe large datasets. The EOFs are generated from a seasonal dataset consisting of 12 SSPs collected once every month of the year at the same location. Inversion is formulated as an optimization problem and solved by employing the method of Differential Evolution Algorithm. A ray-theory based forward propagation model is implemented to model multipath arrival times with candidate SSPs, reconstructed from the EOFs as input for the two source receiver ranges. The objective function measures mismatch between the observed and modeled travel time estimates. The SSP estimated from modeled arrival times with EOFs as search space is found to agree reasonably well with in situ SSP for the two ranges.

The stress-strain relation in a transversely isotropic (TI) material is described by five independent parameters. In the incompressible limit, only three parameters are required to describe shear wave propagation. Existing material parameterization models are not ideal for the analysis of wave propagation in the nearly incompressible TI (NITI) regime due to difficult-to-interpret parameters, complicated forms of the stiffness matrix elements, or the lack of five independent parameters. This study describes a new parameterization model for a general, TI material that uses the bulk modulus K, shear moduli μT and μL, a modulus-like term μE, and a new parameter η. In the proposed parameterization model, each parameter has a clear interpretation related to compressibility and shear wave propagation. The incompressible limit is represented by the limit K → ∞. Wave speeds and polarizations are derived and evaluated in both incompressible and NITI regimens. First-order NITI corrections are shown to be inversely proportional to the ratio of bulk modulus to shear moduli. In biological soft tissues, this ratio is approximately 106. NITI corrections depend on all five independent parameters; however, the small scale of these corrections validates previous studies that have assumed particular values for the parameter η.

Power-law adaptation is a form of neural adaptation that has been recently implemented in a popular model of the mammalian auditory nerve to explain responses to modulated sound and adaptation over long time scales. However, the high computational cost of power-law adaptation, especially for longer simulations, means it must be approximated to be practically usable. Here, a straightforward scheme to approximate power-law adaptation is presented, demonstrating that the approximation improves on an existing approximation provided in the literature. Code that implements the new approximation is provided.

The soundscape approach provides a basis for considering the holistic perception of sound environments in context. Whereas steady advancements have been made in methods for assessment and analysis, a gap exists for comparing soundscapes and quantifying improvements in the multidimensional perception of a soundscape. To this end, there is a need for the creation of single value indices to compare soundscape quality which incorporate context, aural diversity, and specific design goals for a given application. Just as a variety of decibel-based indices have been developed for various purposes (e.g., LAeq, LCeq, L90, Lden, etc.), the soundscape approach requires the ability to create original indices for different uses, which share a common language and understanding. Therefore, a unified framework for creating bespoke and reference single index measures of soundscape perception is proposed, allowing for different metrics to be defined in the future. This framework is based on a four-step test-target paradigm wherein a desired soundscape perception is defined as a target distribution within the soundscape circumplex, and the two-dimensional Kolmogorov-Smirnov distance is used to test an assessed soundscape against this target. Applications and implications of this framework are discussed, and a multi-objective optimisation method for empirically defining perception indices is proposed.

This study examines whether cue integration in tone perception undergoes changes caused by disparities in language experience among two groups of multidialectal speakers from Changsha: participants in the dialect-preserving group speak Changsha dialect (CD), Changsha Plastic Mandarin (CPM), and Standard Mandarin (SM), whereas participants in the dialect-lost group speak CPM and SM but not CD. An identification test on T1 and T4 was conducted, both of which are present in the CD and CPM. T1 and T4 are associated with a high pitch, but they differ in pitch height, pitch contour, and voice quality. In particular, T4 is associated with a tense voice quality. The results showed that F0 height is the primary cue for distinguishing T1 and T4 by both groups. Voice quality affects the perception of the dialect-preserving group, but it does not have an impact on the perception of the dialect-lost group. Alternatively, F0 contour plays a more important role in T1/T4 perception for the dialect-preserving group than for the dialect-lost group. This suggests that differences in language experience caused by dialect loss affect the use of F0 and voice quality cues in tone perception.

The Lambert diffuse reflection model is used widely in computerized prediction of sound in rooms as well as for outdoor scenarios. One seemingly surprising consequence of the model was pointed out by Borish [J. Audio Eng. Soc. 34, 539-545 (1986)]: A diffusely reflecting, non-absorbing wall seems to give a 3 dB stronger reflection than a specularly reflecting wall for a source and receiver along the same plane normal. Similar observations have been made by others, and it is usually commented that the two reflection types distribute the reflected energy in different directions. The aspect of energy conservation does not seem to have been sorted out entirely. It is shown here that the difference between an omnidirectional receiver, like a microphone, and a surface element receiver, which can give the total reflected power, explains the claim. Analytic solutions and numerical evaluations of the well-known integrals for a single infinite wall confirm that energy conservation is indeed maintained and also lead to a spatial distribution of the Lambert reflection strength, which differs substantially from the previously published values. The special case can serve as a useful benchmark test of implementations of diffuse reflections, which follow Lambert's law.

Space-time modulation opens the door for unprecedented wave behavior control, such as nonreciprocal wave manipulation. Here is proposed a one-dimensional space-time modulated membrane system aiming to realize a kind of acoustic metamaterial with space-time modulated effective density. Three different approaches, namely, the effective medium method, transfer matrix method, and time-domain simulation, are applied to analyze the acoustic response of the system under a monochromatic incidence. Results show that the proposed metamaterial can support two different nonreciprocal acoustic functionalities, namely, unidirectional parametric amplification and parametric frequency conversion, when different modulation profiles are enforced.

A primary feature of bat and dolphin biosonar is the ability to measure echo-delay, both to determine absolute target range and to resolve range differences between targets. Measurements of range (i.e., echo-delay) discrimination thresholds in echolocating animals, however, vary across studies. This variance may reflect different test methods, such as whether the animal could simultaneously receive echoes from two compared targets (simultaneous condition), or only one target at a time (successive condition). The present study compares these test conditions directly in a dolphin. Dolphin echo-delay discrimination thresholds were measured under both simultaneous and successive conditions at simulated mean ranges of 3, 10, and 14 m to assess potential interactions across target range. The potential for spectral cues at various range differences under a simultaneous condition was also evaluated using a model of the dolphin peripheral auditory system. Results indicate that the availability of spectral cues during the simultaneous condition imparted limited improvement relative to the successive condition where spectral cues were unavailable. Echo-delay discrimination thresholds showed an overall increase with an increase in range in both the simultaneous and successive conditions.

Underwater noise data were collected from 84 pile drives during bridge construction at various sites in Florida. These data were used to develop an empirically based model for underwater transmission loss associated with root mean squared, peak, and sound exposure level values. The model was verified using readings from other datasets as well as data from this study, and it appeared to reproduce reported transmission loss coefficient values well when data were curated to match data used in the empirical model's development and limited to situations where robust data were used in model development. As such, the model described here has some limitations, but in the context of pile driving in Florida where most piles are of similar dimensions and driven in similar water depths, especially during impact pile driving concrete piles, it may represent a useful design tool that engineers can use to predict underwater noise due to pile driving without the need to sample sound at multiple locations during driving.