Journal of the Acoustical Society of America最新文献

Pile driving for offshore wind turbines typically generates high sound levels in the water column. Bubble curtains are frequently employed to protect marine fauna. This study aims to investigate the effect of a bubble curtain on the generated sound wave field. A recently developed seismo-acoustic model was extended by incorporating an established acoustic model of the bubble curtain. Subsequently, a detailed analysis of the sound wave field at an offshore wind farm construction site was conducted using both simulated and measured data. The results indicate a distance- and depth-dependent insertion loss, with reductions of approximately 2 to 4 dB observed at greater distances from the pile. For a more detailed analysis, a metric based on the concept of transmission loss was introduced. This demonstrates that the insertion loss caused by a bubble curtain can be formulated as a sum of two components: the loss due to the interaction between the bubbles and the sound wave field, and the altered bottom loss resulting from the scattering of the sound wave as it passes through the bubble curtain. Analysis of the simulation data highlights that sound scattering and the resulting altered bottom loss significantly contribute to the efficiency of the bubble curtain.

In adaptive beamforming, the array signal processing adjusts its sensor delays and weights based on the incoming data. In conventional beamforming, these parameters are instead given from a predefined model. Adaptive beamformers can improve measurement precision by dynamically rejecting spatial interference. While an established theory is available on the behavior of adaptive beamformers in textbook scenarios, their expected performance on realistic pulse-echo imaging scenes is still mostly uncharted. Imaging performance can be evaluated by individual pixel precision and aggregated metrics such as resolution and contrast. The achievable gain is strongly related to the sparsity of the scene and the availability of data to appropriately estimate the spatial covariance matrix. In pulse-echo measurements, the nonstationary interference poses a special problem for adaptive beamforming, which is a current research question of academic and industrial interest. The current work establishes a performance bound for adaptive beamforming in simulated realistic pulse-echo scenarios. This is derived and numerically implemented as the clairvoyant minimum variance distortionless response beamformer. The proposed framework allows for an a priori assessment of the applicability of adaptive beamforming, for a given scenario. The performance of the implemented algorithms can be directly compared with the theoretical limit in a simulated environment.

To measure the electroacoustic parameters of transducers in the continuous sound field in a limited water area, a reciprocity calibration method of hydrophones using a spatial sampling average method in a non-anechoic tank was developed. The sound propagation in the non-anechoic tank under the impedance boundary condition, with a sound source producing continuous sound, is introduced based on the Helmholtz equation and Green's function. The reciprocity constant is given using the spatial sampling average sound pressure, and the three-transducer reciprocity calibration procedure was established. The number of spatial sampling points, which must be not less than 6000, and the sampling configuration in the non-anechoic tank are determined. In the non-anechoic tank of 15 m × 9 m × 6 m, the sensitivity of the hydrophone in the frequency range of 250 Hz to 10 kHz was calibrated, and the largest discrepancy between the measurement results from the reciprocity calibration method in the non-anechoic water tank and the standard facility was 0.7 dB.

Low frequency noise (LFN) of unknown origin can be disturbing, especially at night, and affect sleep and relaxation. If reduction of the LFN is impossible, adding sound can mask the troubling noise or detract attention from it to reduce distress. To assess the effectiveness of this, a survey was set up consisting of three questionnaires: the first when a person requested a masking sound and follow-ups after 1 and 3 months. Distress reduction was based on self-assessment and on the tinnitus questionnaire (TQ). Out of 124 respondents, 69% reported that the masking sound contributed to a reduction in complaints, resulting in a reduction in TQ score. Respondents were mainly above 50 years of age and 31% were male. Most respondents (84%) denounce the possibility of an internal sound. However, demographic characteristics of respondents are more similar to tinnitus patients and less to residents annoyed by environmental noise. The number of respondents per capita rises with decreasing population density, indicating that a quiet environment enhances the hearing of LFN. Thus, absence of sound in the environment may induce the hearing of LFN.

Previous studies suggested that pitch characteristics of lexical tones in Standard Chinese influence various sensory perceptions, but whether they iconically bias emotional experience remained unclear. We analyzed the arousal and valence ratings of bi-syllabic words in two corpora (Study 1) and conducted an affect rating experiment using a carefully designed corpus of bi-syllabic words (Study 2). Two-alternative forced-choice tasks further tested the robustness of lexical tones' affective iconicity in an auditory nonce word context (Study 3). Hierarchical linear models, generalized linear mixed models, and cross-validation were employed to understand the relationship between lexical tones and the emotional responses of tone-carrying words. Results consistently indicated that words with a falling-falling tonal sequence, both real and nonce words, received higher arousal ratings than those with rising-rising and rising-low tones. Only in nonce words, the high-high sequence was more likely to be associated with the low-arousal option; the falling-falling tone sequence was more often linked to negative-valence choice, while high-high and rising-rising tones with positive-valence. These findings, though subtle, suggest that the use of pitch in lexical tones influences emotional responses during the processing of tone-carrying words, pointing to an inherent iconic quality in lexical tones that may subtly shape speakers' emotional experiences.

Inhomogeneous media made of random configurations of coated circular cylinders are considered. The effective properties-wave number, mass density, bulk modulus-are discussed and illustrated. The effects of the volume fraction of the scatterers and surrounding fluid are also examined. Estimations of the effective bulk modulus and mass density are provided at the static limit with the aim of generalizing some existing results for uncoated cylinders to multicoated ones. In all cases, time harmonic waves are scattered and the Norris and Conoir [J. Acoust. Soc. Am. 129, 104-113 (2011)] multiple scattering expansion for the effective wavenumber used to derive the properties.

Fishes and aquatic invertebrates utilize acoustic particle motion for hearing, and some additionally detect sound pressure. Yet, few underwater soundscapes studies report particle motion, which is often assumed to scale predictably with pressure in offshore habitats. This relationship does not always exist for low frequencies or near reflective boundaries. This study compared particle motion and sound pressure from hydrophone arrays near the seafloor at six sites on the U.S. Mid and South Atlantic Outer Continental Shelf and assessed predictability of sound pressure and particle motion levels by environmental indicators (wind, vessels, temperature, currents). Unidentified fish sounds (100-750 Hz) had particle motion magnitudes 4.8-12.6 dB greater than those predicted from single hydrophone (pressure) measurements, indicating that these sounds were received in the near field. Excess particle motion attributed to hydrodynamic flow noise (<100 Hz) was also present at all sites. Most sounds (25th-75th percentile) from other sources received in the far field (vessels, mammals), had measured particle motion within ±3 dB of that predicted from single hydrophone measurements. The results emphasize for offshore soundscapes the importance of particle motion measurement for short-time (1 min) and near field signals, and that pressure measurement is sufficient for long-term (1 year) predictive modeling.

In shallow water, reverberation complicates the detection of low-intensity, variable-echo moving targets, such as divers. Traditional methods often fail to distinguish these targets from reverberation, and data-driven methods are constrained by the limited data on intruding targets. This paper introduces the online robust principal component analysis and multimodal anomaly detection (ORMAD) method to address these challenges. ORMAD efficiently performs online low-rank and sparse decomposition while utilizing unsupervised multimodal anomaly detection to enhance detection performance. The multimodal anomaly detection process involves two phases: modality extraction and anomaly detection. During modality extraction, echo data are separated into echo structure and spatial trajectory modalities, providing complementary information that improves the network representation of both reverberation and moving targets. The subsequent anomaly detection phase unsupervisedly learns the modalities of fluctuating reverberation, thereby achieving stable reconstruction while maintaining sensitivity to moving targets. This sensitivity allows effective identification of moving targets by detecting reconstruction loss. Experimental results demonstrate that ORMAD effectively improves detection performance in complex reverberation scenarios. In a real-world sonar dataset, ORMAD increased the average precision for detecting diver targets from 60% to 75% compared to the state-of-the-art method.

In this paper, an improved version of the classical equivalent radiated power (ERP) approximation is proposed based on principled physical arguments. A geometry-, frequency-, and vibration pattern-dependent approximation of radiation efficiency is developed and used as a corrective factor for the classical ERP approximation. The proposed method called "radiation efficiency varying equivalent radiated power" (revERP), is shown to greatly improve the accuracy of classical ERP at low Helmholtz numbers, while attaining the accuracy of classical ERP at high Helmholtz numbers. The revERP method is exemplified on several components of industrial complexity, and shows a valuable alternative to full vibro-acoustic finite element analysis for early-stage assessment of acoustic performance.

Th e Laplace transform formulation proposed by Di and Gilbert [J. Acoust. Soc. Am. 93, 714-720 (1993)] is an efficient and accurate method for calculating the half-space Green's function. However, the integral upper limit required in this formulation has not been examined in the context of an extended reacting reflecting plane, which is a critical parameter influencing both the accuracy and efficiency of the formulation. In this article, the Laplace transform formulation is further explored, and a novel method is proposed for identifying the integral upper limit, which is verified through numerical studies.