Journal of the Acoustical Society of America最新文献

The impact of a chromium (Cr) coating on the elastic guided waves propagating in zirconium alloy (called M5 Framatome and referred to as M5 hereafter) nuclear cladding tubes is studied both theoretically and experimentally. Longitudinal modes are measured on different 9.5 mm-diameter tubes by a non-contact laser ultrasonic technique. These modes are calculated using the M5 elastic constants determined from x-ray diffraction measurements. Since Cr has a much higher shear wave velocity than the M5 alloy, the dispersion of observed guided modes is significantly modified by the coating. In the mid-frequency range, characterized by shear wavelengths on the order of the tube thickness, the second longitudinal mode appears to be particularly sensitive to the coating. In a higher frequency range, it is observed that modes are well measured in a frequency-wavenumber domain corresponding to the leaky surface wave of a Cr coated infinite M5 substrate. A simple but effective model predicts the observability of each mode, in good qualitative agreement with experimental observations.

With development of intelligent cabin, specialized psychoacoustic evaluation method is needed to link subjective and objective parameters for audio quality design in vehicle cabins, in which traditional psychoacoustic metrics are limited in capturing multidimensional perceptual differences. This study proposes a pentatonic harmonic audio system evaluation (PHASE) framework to evaluate audio quality in vehicle cabins. The reverberation time and frequency responses were measured in five representative cars. The harmonic features were derived from the frequency responses based on the pentatonic scale. Six music clips were recorded in driver's and rear-right seats to generate ten sets (five driver's seat, four rear-right seats, and one baseline) of stimuli for evaluation. Subsequently, 50 participants evaluated audio quality for all stimuli on the 100-point scales across 9 dimensions: timbre brightness/darkness, timbre warmth/coolness, clarity, distortion, dynamic range, bass quality, spatial impression, localization, and distance. The evaluation models were established through multiple linear regression between the subjective rating values and harmonic features. These models showed strong explanatory power (R2 = 0.852 - 0.987) across all dimensions, effectively capturing multidimensional in-vehicle auditory perception. The PHASE framework demonstrates strong potential for evaluating audio quality in enclosed or irregular acoustic environments such as immersive virtual spaces and home theaters.

Underwater acoustic measurements made with vertical line arrays (VLAs) can exploit horizontal sound speed stratification to resolve dominant signal propagation paths and elevation angle-dependent ambient noise structure. Leveraging this attribute of vertical aperture, a non-parametric approach to source depth discrimination is introduced. The approach is distinguished by its lack of reliance on a priori knowledge of the sound speed environment or modeling of the channel's depth-dependent normal mode functions. Instead, the method relies solely on a measurement of the vertical wavenumber spectrum associated with the principal eigenvector of the array spatial cross-covariance estimate. It will be shown that, given sufficient vertical aperture, the principal eigenvector is an estimator of the dominant normal mode or modes excited by the source. Two methods for estimating the vertical wavenumber spectrum from the principal eigenvector are presented: conventional (or fast Fourier transform-based) and minimum variance distortionless response. For both methods, implementation issues and differences in spatial resolution will be examined. Depth discrimination performance will be quantified using receiver operating characteristic curves developed from at-sea experimental data collected on a 32-channel vertical line array deployed from a Liquid Robotics SV-3 wave glider (Liquid Robotics, Herndon, VA) in downward-refracting conditions off the coast of San Diego, CA, in August 2017.

The relationship between vocal tract geometry and acoustic resonances is often examined using speaker-specific data, limiting physical studies to a narrow set of static, rigid configurations and frequently producing discontinuous area functions that are poorly suited for studying dynamic vocal-tract behavior. To address these constraints, this study introduces a theoretical squeezed waveguide vocal tract (SWVT) framework for analyzing the relationship between acoustic resonances (up to 4-5 kHz) and smooth area functions that characterize vowel-like vocal tract configurations with one or two constrictions. The relevance of seven SWVT parameters-constriction positions, degrees, extents, and waveguide length-is established through theoretical analysis and experimental validation. Experiments are performed using both rigid, static waveguides and a deformable, molded waveguide. The molded waveguide facilitates experimental investigation of constriction degrees up to full closure and provides a basis for future studies on the (aero-)acoustic-geometry relationship in dynamic SWVT configurations.

Urban road traffic noise is a growing environmental concern, and noise masking offers an alternative solution. However, the underlying neural mechanisms of natural sound masking of noise remain unclear. Here, the brain's physiological responses to natural sound masking (birdsong and water sound) were explored using functional near-infrared spectroscopy. The functional connectivity between brain regions was analyzed by graph-theoretical network analysis, and the subjective annoyance was correlated with brain activation and graph-theoretical network parameters. Results revealed that masking conditions significantly reduced annoyance compared to the road traffic noise condition. Birdsong and water sound masking increased activation in the right superior temporal gyrus and right middle temporal gyrus, which is positively correlated with the annoyance reduction percentage. Birdsong masking globally decreased the connections between brain regions and neighboring regions at the group level, which is negatively correlated with the annoyance reduction percentage. These findings demonstrate that natural sound masking can modulate brain network topology and functional connectivity, offering insights into effective noise-masking strategies.

The role of medial olivocochlear (MOC) efferent gain control in auditory enhancement (AE) was investigated using a subcortical auditory model. AE refers to the influence of a precursor on detectability of targets. The absence (or presence) of a precursor component at the target frequency enhances (or suppresses) detection under simultaneous masking conditions. Furthermore, the enhanced target under simultaneous masking acts as a stronger forward masker for a delayed probe tone, known as AE under forward masking. Psychoacoustic studies of AE report findings that challenge conventional expectations, and the underlying mechanisms remain unclear. For instance, listeners with hearing impairment have AE under simultaneous masking but not forward masking [Kreft, Wojtczak, and Oxenham (2018). J. Acoust. Soc. Am. 143(2), 901-910; Kreft and Oxenham (2019). J. Acoust. Soc. Am. 146(5), 3448-3456], whereas listeners with normal hearing have level-dependent AE under forward masking [Kreft and Oxenham (2019). J. Acoust. Soc. Am. 146(5), 3448-3456]. Our model with MOC efferent gain control successfully replicated these findings. In contrast, a model without efferent gain control failed to capture these effects, supporting the hypothesis that MOC-mediated cochlear gain modulation may play a role in AE and its alteration by hearing loss.

Time histories of broadband ship noise measured at the Lofoten-Vesterålen cabled observatory (on the seafloor at 255 m depth in the Norwegian Sea) are compared to model-based predictions. Fifty-four tracks of 26 different vessels are included in our analysis; all 54 ship tracks pass within 520 m horizontally of the hydrophone. Ships were tracked using the Automated Identification System. A striking feature of the ship noise measurements is azimuthal anisotropy of the sound radiated by the passing ships; sound intensity aft of the vessels is higher than sound intensity fore of the vessels. Anisotropy of the radiated ship noise is accounted for in the ship noise propagation model used. Agreement between measurements and model predictions is good. Estimates of ship-radiated acoustic power and an azimuthal anisotropy strength parameter are obtained for each ship track. Estimates of the azimuthal anisotropy strength parameter depend on vessel type. Estimates of the azimuthal anisotropy strength parameter among different tracks of the same vessel show considerable variability, and estimates of radiated acoustic power show no clear increase with increasing ship speed; these unexpected results suggest that factors not accounted for in our analysis, including ship displacement, play a role in controlling the radiated ship noise.

The Reflections series takes a look back on historical articles from The Journal of the Acoustical Society of America that have had a significant impact on the science and practice of acoustics.

Momentum bias within one-dimensional elastic media introduces non-reciprocal phenomena in the propagation of elastic waves, manifesting as Willis coupling in the governing wave equation. To the best of our knowledge, the implications of Willis coupling being the sole coupling mechanism within elastic media and the understanding of non-reciprocity through finite structure analysis remain unexplored. In this paper, a non-reciprocal wave phenomenon with pure Willis coupling is synthesized using feedback control in mechanical lattices consisting of masses, grounded springs, and linear actuators. The proposed system presents a unique lack of physical connections between masses, allowing for pure Willis coupling through feedback forces exerted by the linear actuators. The dynamical behavior of a unit cell segment from an infinite lattice chain is considered, and the emergent non-reciprocal dispersion relation is detailed, including an analytical quantification of the Brillouin-zone translation resulting from pure Willis non-reciprocity. Analytical derivations of the eigenpairs of a finite lattice configuration are established, and the theoretical analyses reveal the mechanism of non-reciprocity through the lens of the lattice's natural frequencies and corresponding mode shapes.

This study introduces directional coherence loss coefficients (DCLCs) to quantify the angular distribution of sound field coherence loss, which arise from localized scattering distributions within an enclosure, from a receiver's perspective. Sound fields in the room are sampled by a spherical receiver and decomposed into plane waves using spherical harmonics expansion, yielding directional impulse responses (IRs). The time-dependent coherence coefficients between directional IRs in furnished rooms and their empty counterparts are analyzed for each direction. DCLCs are derived from these coherence coefficients and decide the transition between the coherent component-mainly representing specular reflections-and the incoherent component, accounting for scattering contributions from interior elements. This research extracts DCLCs from rooms with varying transducer positions founded on wave-based simulations and measurements from rooms with different element distributions. A hybrid model is proposed to reconstruct the sound field in a room with a single diffusive wall, where the coherent component is computed from the empty room case, and the incoherent component is simulated stochastically, with their relative weighting decided by DCLCs. Directional IRs from the hybrid model exhibit agreement with ground truth in terms of reverberation time, clarity, kurtosis, and spatial cross correlation coefficients, verifying the ability of DCLCs to characterize localized scattering distributions in enclosures.