Journal of the Acoustical Society of America最新文献

The effect of a changing ocean environment on sound propagation across the Gulf Stream near the New England Seamount chain is investigated using satellite altimetry and hydrographic profiles from a large set of Argo floats. Reconstruction of the Gulf Stream vertical structure is accomplished by use of an altimetry-informed gravest empirical mode (AGEM) method. The AGEMs act as transfer functions allowing for the estimation of 3D, interior sound speed fields from 2D, surface altimetry measurements. AGEMs are constructed using empirical relationships between the steric height and the temperature and salinity profiles in the region. Ray tracing and parabolic equation sound propagation models are employed to identify changes in propagation patterns over the 14-year interval between 2009 and 2023. It is found that there has been a reduction in the travel time to a range of 120 km caused by increased temperatures throughout the water column associated with a warming Gulf Stream. It is also observed that the structure of the sound speed gradient field has changed over the decadal window, causing differences in sound propagation interference patterns on the far side of the Gulf Stream.

The Ocean Observatories Initiative (OOI) provides continuous monitoring of acoustic fields at various locations in the northeast Pacific Ocean, among other types of data. The effects of marine seismic reflection surveys on the ambient soundscape in the vicinity of these hydrophones can be quantified by looking at OOI hydrophone data in conjunction with cruise documentation. Two seismic reflection surveys, MGL1905 and MGL2104, and measurements on three hydrophones at varying depths with 64 kHz sampling rates are considered. The seismic air guns are exhibited to raise the mean ambient sound by up to 30 dB over several one-third octave bands, where the impact varies significantly as a function of range, depth, and other factors. Effects can be observed hundreds of kilometers from the air gun arrays, and shots may be frequent enough that the ambient sound does not return to its pre-cruise background levels between shots. Although range is strongly correlated with these effects, metrics, such as sound exposure level or sound pressure level, can easily vary by 10 dB or more at the same range.

Incorporating head-tracking techniques into local active noise control headrest systems enables the plant model used in the controller to be updated dynamically as the user moves their head. This reduces the mismatch between the plant model and the physical plant responses from the secondary sources to the users' ears, which increases the achievable noise reduction when head movement occurs. In practice, since the plant models for different head positions must be identified during a calibration procedure, it is necessary to limit the head-tracking resolution to constrain the complexity of this procedure. This leads to errors between the physical and modelled plant responses as the user's head moves, which impacts the control system's stability and performance. However, the relationship between the control system behaviour and the tracking accuracy is not well understood. This paper investigates the impact of head-tracking resolution, considering translational and rotational movements, on the stability and performance of an active headrest. Assuming the error signals at the user's ears are available for adaptive control, it is shown that the system has an upper-frequency limit beyond which controller instability occurs, and this frequency is influenced by the tracking resolution, the initial head position, and the type of head movement.

This joint Special Issue of JASA and JASA Express Letters focuses on underwater sound source and propagation modelling, both of ambient sound as well as sources of relevance to possible effects of sound on aquatic life, and corresponding acoustical metrics. Combining information on the sound field with information on a dose-effect relationship enables estimation of the potential effects. The Special Issue presents a collection of eighteen articles on the following topics: (1) verification of source and propagation models, (2) validation of source and propagation models, and (3) bioacoustical metrics for assessment of the risk of environmental effects. This special issue demonstrates the need for clear metrics and verification and validation protocols.

Studies are increasingly investigating listeners' acoustic environments using real-world data collection methods to personalize interventions for hearing loss and understand individual differences in intervention outcomes. A pressing methods question is the extent to which the time scale of the sample and number of sampling periods need to be considered. The purpose of this study was to characterize the extent to which the sound levels in a listener's vicinity, one common measure of acoustic environments, change across different time scales. Listeners wore a personal noise dosimeter continuously for one-week sampling periods at three time points. The effects of season, week, day of the week, and time of day on acoustic environment demand (proportion of samples ≥ 40 dB LAeq and mean sound levels for samples ≥ 40 dB LAeq) and diversity (the distribution of LAeq values, quantified by entropy) were characterized. Acoustic environment demand and diversity were relatively similar across seasons and weeks but varied more between days and across the day. Results suggest that a single one-week sampling period, collected at any time of year but balanced across days of the week and time of day, may capture sufficient information about a listener's acoustic environments to inform decisions about interventions.

This study evaluates the performance of subharmonic-aided pressure estimation (SHAPE) with ultrasound contrast agents using data obtained from calibration procedures. A commercial scanner of ultrasonography (GE Healthcare Logiq E20, Wuxi, China) was used to perform SHAPE on a flowing contrast agent (Sonazoid) in a phantom setup under controlled microbubble stability and flow velocity conditions. Subharmonic time-intensity curves were collected during the SHAPE calibration procedure for analysis. Subharmonic amplitude of diluted contrast agents exhibited a time-dependent decline but was not affected by velocity. SHAPE sensitivity was measured through reciprocal pressurizing and depressurizing sequences to mitigate the effect of subharmonic decline over time. A wide range of mechanical index (MI) levels within the steady growth phase of the calibration curve showed higher SHAPE sensitivity compared to the traditionally recommended "optimal" MI at the maximum slope. The approximate maximum SHAPE sensitivity was -0.04 dB/mm Hg. Subharmonic amplitude was linearly correlated with pressure at a range of MI levels (R2 > 0.9, p < 0.05) but showed significant variations (approximately 2 dB standard deviation) in the time series. The lowered sensitivity compared to previous reports, combined with the substantial variation in subharmonic amplitude, raises concerns about the accuracy and consistency of SHAPE in clinical applications.

Higher-order stereophony is a new approach for spatial audio reproduction which extends classic two-channel stereophony to higher order soundfield reproduction and generalised multi-channel loudspeaker arrays. Higher order stereophony achieves accurate soundfield reproduction over a line by reproducing the degree m = 0 spherical harmonic soundfield coefficients only. The reproduction line is assumed to align with the interaural axis of a listener. This article addresses the extension of higher order stereophony to binaural reproduction. The technique is shown to exactly reproduce binaural signals when using a rigid sphere head-related transfer function model, and to reorder the energy of more generalised head-related transfer functions into spherical harmonic coefficients with degree index close to 0. To truncation order N, higher order stereophony requires only (N + 1) spherical harmonic coefficients compared to (N + 1)2 with higher order ambisonics, and the two techniques are compared through simulations and a listening test. Higher order stereophony is shown to perform similarly to higher order ambisonics under truncation to the same order, but using a smaller number of soundfield coefficients. For higher virtual source elevations, higher order stereophony performs worse than higher order ambisonics due to its ability to only reproduce axisymmetric head-related transfer functions.

Feature-aided tracking integrates supplementary features into traditional methods and improves the accuracy of data association methods that rely solely on kinematic measurements. However, previous applications of feature-aided data association methods in multi-target tracking of passive sonar arrays directly utilized raw features for likelihood calculations, causing performance degradation in complex marine scenarios with low signal-to-noise ratio and close-proximity trajectories. Inspired by the successful application of deep learning, this study proposes BiChannel-SiamDinoNet, an advanced network derived from the Siamese network and integrated into the joint probability data association framework to calculate feature measurement likelihood. This method forms an embedding space through the feature structure of acoustic targets, bringing similar targets closer together. This makes the system more robust to variations, capable of capturing complex relationships between measurements and targets and effectively discriminating discrepancies between them. Additionally, this study refines the network's feature extraction module to address underwater acoustic signals' unique line spectrum and implement the knowledge distillation training method to improve the network's capability to assess consistency between features through local representations. The performance of the proposed method is assessed through simulation analysis and marine experiments.

Improving the underwater three-dimensional imaging resolution of a sonar system is of great significance to achieving high-precision ocean exploration results. Actually, improving the resolution can be considered from the perspective of information acquisition. The acoustic orbital angular momentum (AOAM) wave has a modal dimension and can carry more target information. However, there are few studies on the application of AOAM waves for underwater three-dimensional imaging. This paper establishes the related signal models of the AOAM wave in underwater imaging and examines the sound field characteristics from both simulation and underwater real test data. A method called mode matching beamforming (MMBF) is proposed, and a composite structure of uniform circular array (UCA) plus spiral array is combined to study the imaging performance of AOAM waves and plane waves. The simulation results indicate that, compared with the plane wave, the sidelobe in the AOAM wave imaging beam pattern reaches -22.43 and -29.10 dB in the azimuth and elevation angles, respectively, and the mainlobe widths are reduced by 1.70° and 0.40° in both directions. Finally, this paper uses the MMBF method to process the echo data of underwater real object and realizes the imaging of the corner reflector.

Wavelet scattering is a highly effective feature extraction method, prevalent in many other fields. This paper introduces wavelet scattering to the field of passive acoustic monitoring, employed to test its relevance to the field using a manually verified subset of an open access dataset. Additionally, we introduce an adaptive whitening method to increase detection efficacy. This approach is shown to be most performant with a spectral entropy detector enhanced by a novel thresholding technique. We demonstrate that a simple classifier trained with little data and utilizing wavelet scattering features can greatly improve the performance of the proposed spectral entropy detector. The efficacy of our method is demonstrated on Antarctic blue whale (Balaenoptera musculus intermedia) calls.