Journal of the Acoustical Society of America最新文献

The high electrical output performance of the phononic crystal (PnC)-based piezoelectric energy harvesting (PEH) system is of great research value in self-powered applications. This work presents the effect of incomplete line defect size on elastic wave energy localization and harvesting. The results show that for a given 7 × 5 supercell when the incomplete line defect reaches the second to sixth layer, the energy localization and harvesting performance show a changing trend of first increasing and then decreasing; when the incomplete line defect reaches the 4th, 5th, 3rd, 2nd, and 6th layers of the supercell, respectively, the performance of PEH systems shows a trend from large to small. Among them, when the incomplete line defect reaches the fourth layer of the supercell, the performance of the PEH system is optimal, and the maximum output voltage and the maximum output electric power are 22.54 V and 12.78 mW, respectively. This work provides valuable insights for improving the performance of PEH devices by using the PnC with incomplete line defects.

Zero-directional refraction phenomenon refers to the capability where waves do not undergo refraction at a material interface under specific conditions, which has broad potential applications, particularly in the fields of optics, acoustics, and phononics. Previous research of zero-directional refraction rely on the zero or equivalent-zero index of the material parameters, which is quite challenging to manipulate the zero-directional transport of waves. In this paper, based on the topological theory, we have constructed a pillared phononic crystal (PnC) plate structure with pseudospin topologically protected transport, enabling zero-directional refraction of elastic waves without using zero or equivalent-zero index of the material parameters. By initially adjusting the contraction and expansion of the pillared unit cell, a band inversion effect between pseudospin dipoles and quadrupoles is induced, thus leading to a topological phase transition of elastic wave. Combining the phase matching between topological interface and terminal medias, the elastic waves in pillared PnC plate can exhibit zero-directional refraction behavior. Finally, it was demonstrated that the phenomenon of zero-directional refraction exhibits robustness in the presence of cavities and bends, and different incident angles. This research result provides new insights for designing and manipulating the emission and directional antennas of elastic waves.

Deploying acoustic sensors on free-flying, long-living balloons helps to reach the areas not accessible with the traditional ground-based sensors, reduce flow noise, and improve characterization of various infrasound sources. Instrumented balloons can potentially increase the infrasonic detection range and early warning lead time for natural hazards. Balloons are also considered as platforms for planetary exploration. When assessing the capabilities of balloon-borne infrasonic sensors and interpreting the measurements, it is imperative to recognize that the balloon inevitably distorts the signals and background infrasound field by scattering the incoming sound. This paper quantifies the effects of hot-air and helium balloons on acoustic pressure and particle acceleration and the role of balloon skin in infrasound diffraction. It is found that balloon-borne vector sensors are more susceptible to distortions than pressure sensors, leading to major differences between the apparent and true source bearing and directionality.

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.