Journal of the Acoustical Society of America最新文献

Underwater acoustic coatings play a vital role in minimizing noise and enhancing stealth capabilities by maximizing sound absorption performance. In this study, we introduce a reinforcement learning-based topology optimization (RL-TO) method for designing underwater acoustic coatings that achieve broadband and low-frequency sound absorption. The RL-TO approach integrates reinforcement learning with a systematic topology optimization framework to dynamically explore optimal material distributions and structural configurations. The optimized topologies exhibit distinct characteristics, such as waveguiding at low frequencies and local resonance at high frequencies, demonstrating enhanced absorption performance across a wide frequency range. Further parametric studies on triangular-shaped wave controllers and spherical resonators highlight the importance of geometric features in achieving superior absorption. The proposed method achieves an average absorption coefficient exceeding 0.9 for multiple target frequencies while maintaining robust performance. This study establishes RL-TO as a powerful and efficient design tool for underwater acoustic coatings, offering significant advancements over conventional approaches.

Building-generated turbulence can significantly influence the propagation of noise from advanced air mobility (AAM) vehicles operating in urban environments, yet its impact on acoustic variability remains poorly quantified. In this study, the effect of an isolated building wake on sound propagation is investigated using time-resolved Lattice-Boltzmann very-large-eddy simulations. A simplified tonal acoustic source representative of an AAM vehicle is placed downstream of the building, and the resulting unsteady sound field is analyzed within and downstream of the turbulent wake. The results show that wake-induced turbulence produces pronounced temporal fluctuations in the received sound pressure level, with variability exceeding 3 dB in localized regions. These fluctuations extend beyond the physical extent of the wake due to interference effects and reflected propagation paths from the building and ground. Analysis along selected propagation directions indicates a strong correlation between turbulence-induced velocity fluctuations and acoustic variability along direct propagation paths, while this correlation weakens in regions dominated by multiple reflections. The findings emphasize the importance of accounting for unsteady, building-induced flow effects when evaluating AAM noise in urban environments.

Active sonar imaging techniques are essential for underwater target detection and tracking, particularly in the complex acoustic environments of shallow water. One of the major obstacles in these scenarios is reverberation from the seafloor and the sea surface, which can significantly degrade image quality. A core objective in active sonar imaging is applying beamforming techniques to achieve a narrow mainlobe and low sidelobe levels. Although conventional beamforming (CBF) is widely adopted for its simplicity and robustness, it faces intrinsic performance limitations. This study reformulates the beamforming process as a single-snapshot complex-valued least absolute shrinkage and selection operator problem. To address this problem, the complex approximate message passing (CAMP) algorithm is proposed. CAMP enhances computational efficiency by avoiding matrix inversion and improves convergence speed by using the Onsager correction term. Experimental validation in an anechoic pool demonstrates that the proposed method achieves significant imaging performance compared to the CBF method. Additionally, the anechoic pool setup is leveraged to optimize the threshold parameter in the CAMP algorithm. Further validation of a monostatic configuration through lake trials confirms that the proposed method significantly suppresses sidelobe levels and improves image resolution, resulting in cleaner sonar images and improved suppression of background interference.

Communication challenges are exacerbated by noise, particularly for individuals with hearing impairment who may also have ear occlusion from hearing protection devices in occupational settings. These combined effects on speech production are understudied, despite auditory feedback being crucial for speech motor control and thus effective communication. This paper introduces Hearing-Integrated Bilingual Speech Corpus, a comprehensive database for examining speech production across varying levels of noise, ear occlusion, and hearing thresholds. We recruited 49 participants [19 with at least one frequency at ≥ 20 dB hearing level (dBHL)] who completed sentence reading, sustained vowel production, and picture description tasks. We demonstrate the database's utility by analyzing speech level responses in the sentence-reading task. We investigated all three factors categorically and additionally modeled hearing impairment as a continuous variable using pure-tone average (PTA). Key results showed that ear occlusion led to increased speech level, but the relationship exhibited non-linearity. Additionally, preliminary findings revealed that participants with PTA > 15 dBHL spoke louder overall, and a categorical shift occurs around PTA = 15 dBHL, where individuals with greater hearing impairment became less reactive to noise under high occlusion conditions. The considerable individual variability challenges categorical groupings of all investigated variables and highlights the need for individualized modeling approaches.

The study aimed to develop and validate remote hearing detection (audiogram) and discrimination (notched-noise) tests, which used Bayesian active-learning based Gaussian processes, as a binary discriminator between audible and inaudible sounds, and to choose the stimulus parameters. Forty-two participants (aged 48-75 years) performed the two tests remotely using their own equipment. The participants were recruited with pure-tone audiometry known a priori. The agreements between the true and estimated hearing thresholds were assessed using Bland-Altman plots and concordance correlation coefficients (CCC). The notched-noise test was used to derive auditory filter shape parameters, from which equivalent rectangular bandwidths (ERBs) were estimated. The ERBs were correlated with participants' hearing thresholds and compared to published data. The agreement between the true and estimated hearing thresholds ranged between poor and fair (CCC = 0.19 and 0.34), with an average bias (±limit of agreements) of 27.3 (±17.8) dB. This was attributed to the lack of calibration of the participants' equipment. The estimated ERBs followed the trend of published data and were significantly correlated with pure-tone audiometry at 1000 Hz (rs = 0.36). Our findings indicate that the remote detection and discrimination tests can collectively track the breakpoints, slopes of thresholds, and the width of auditory filters.

Sound power is a fundamental characteristic of an acoustic source that is critical to developing radiation models. Current analytical methods for calculating sound power from a collection of monopoles either assume perfect coherence or incoherence. However, partially coherent sources are plentiful in structural acoustics and aeroacoustic applications. This paper expands the approach of Nelson, Curtis, Elliott, and Bullmore [(1987). J. Sound Vib. 116, 397-414], who calculated sound power due to mutual coupling between coherent sources, to allow for partially coherent interactions. This expression is used to find the sound power from quadrupole-like source configurations with varying degrees of coherence. When calculating the sound power, partially coherent interactions are limited by two factors: a coupling distance and the coherence length. A numerical example of a driven plate is used to demonstrate the regions where the partially coherent sound power is most applicable. It is shown that when the system coherence length is larger than about one wavelength, the sound power can be calculated assuming a fully coherent source. A final example is shown for the T-7A jet at MIL and AB engine conditions. Sound power spectra are created from an equivalent source model of partially coherent monopoles and compared to measured far-field spectra.

Beaked whales are elusive deep-diving odontocetes, and their distribution and foraging ecology remain poorly documented in Australian waters. This study presents a passive acoustic monitoring (PAM)-based assessment of beaked whale foraging activity along Australia's Northwest Shelf-a continental shelf region with features typically conducive to beaked whale sustenance. The area is also of economic significance due to ongoing offshore oil and gas production, commercial fishing, and commercial shipping, raising concerns about potential impacts on these deep-diving cetaceans. This study collected year-long underwater acoustic datasets from three deep-water sites in the region. Using a semi-automated workflow based on correlogram visualizations, the study identified beaked whale foraging buzzes-short, rapid echolocation click trains associated with prey capture attempts. Analyses revealed year-round foraging activity, with significantly higher levels at night, but no strong spatial or seasonal variations across the study area. These findings suggest persistent use of the region by beaked whales despite offshore industry presence, underscoring the ecological significance of these deep-water habitats. This study highlights the value of PAM, combined with efficient analytical approaches, for monitoring cryptic species in data-limited, industrialized marine environments.

Modulation statistics of "natural soundscapes" were estimated by calculating the modulation power spectrum (MPS) of a database of acoustic samples recorded in nine pristine terrestrial habitats for four moments of the day and two contrasting periods, differing in precipitation level. In particular, a set of statistics estimating low-pass quality, starriness, separability, asymmetry, modulation depth, and 1/ftα temporal-modulation power-law relationships were calculated from the MPS of the samples and related to geographical, meteorological factors and diel variations. MPS were found to be generally low-pass in shape in the modulation domain with most of their modulation power restricted to low temporal (<10-20 Hz) and spectral modulations (<0.5-1 cycle/kHz). Modulation statistics were distinguished between habitats irrespective of moment of the day and precipitation period with a greater role of modulation depth and starriness. Separability and starriness were found to be related to the global biodiversity decrease from tropical to polar regions, suggesting that the lack of joint high spectral and fast temporal modulations and MPS complexity are important features that may characterise "biophony," the collective sound produced by animals in a given habitat. These findings may help guide research on monitoring auditory behaviours and underlying mechanisms expected to exploit regularities of natural scenes.

Research has acknowledged the substantial impact of short auditory training on performance enhancements, but the neural mechanisms involved are not fully understood. This study aimed to explore these mechanisms by examining the cortical effects of single-session speech-in-noise (SIN) training with spectrally degraded stimuli, using functional near-infrared spectroscopy (fNIRS). Twenty-four young adults with normal hearing participated in SIN training using noise-vocoded stimuli. Behavioral improvements were evaluated 1-3 days after training. fNIRS recordings were taken before training, 1-3 days after training, and again 1-3 days following the second evaluation, employing a pseudorandom block design with speech, noise, and SIN stimuli. Training led to significant improvements in SIN perception, accompanied by a non-significant trend toward reduced oxygenated blood beta values in the left middle temporal gyrus in response to the trained stimuli across training and testing sessions. This pattern is consistent with the possibility of cortical adaptation and increased neural efficiency during processing of degraded auditory input following brief training, with effects that appear to extend beyond the immediate training session. Further research is needed to determine whether similar short-term training approaches could benefit individuals with hearing or speech perception difficulties.