Acoustics Australia最新文献

This paper focuses on the voluteless centrifugal fan and proposes a method to reduce the aerodynamic noise of the fan. Through fluid and acoustic simulations, as well as experimental investigations, the fan is examined. The innovative approach involves the implementation of an anti-vortex ring structure at the impeller front disk of the centrifugal fan, and the influence of this structure on the fan's operational efficiency and noise characteristics is analyzed. Based on this analysis, the structural parameters are optimized to control the vorticity of the impeller, resulting in improved overall performance and noise reduction of the HW355 centrifugal fan. Furthermore, noise simulations are conducted using the Lighthill analogy method, which transforms the coupling of turbulent flow and noise into an acoustic analysis of equivalent sound sources in a quiescent medium. By analyzing the results in the frequency domain, noise directivity characteristics, sound pressure level distribution on the meridional plane, and conducting noise experiments, a comprehensive analysis of the acoustic characteristics of the voluteless centrifugal fan is conducted. The study verifies the optimization effects of the innovative anti-vortex ring structure on the aerodynamic noise of the voluteless centrifugal fan.

A robust and high-resolution deconvolution algorithm based on coordinate correction is developed for a compact conformal array on a three-dimensional (3D) moving platform such as underwater glider. First, the coordinate-correcting conventional beamforming is derived to directly estimate the azimuth of the long-range targets in the geodesic coordinate system for a 3D moving platform array. Then, we improve the extended Richardson–Lucy deconvolution (Ex-RL-dCv) beamforming algorithm utilizing coordinate correction to simplify the bearing estimation model from two-dimensional (2D) to one-dimensional (1D). The improved algorithm corrects the deconvolution point spread function (PSF) dictionary mismatch caused by the platform’s 3D motion, and has lower sidelobes compared with the Ex-RL-dCv algorithm without coordinate correction. Finally, simulations and results from field-trial data processing are presented. The results demonstrate that the improved Ex-RL-dCv beamforming based on coordinate correction can significantly suppress the high sidelobes caused by deconvolution model mismatch, and successfully realize the robust and high-resolution detection for targets using the compact conformal array on a 3D mobile platform.

An apparent disconnect exist in workplaces regarding identification of occupational hearing loss (OHL) and implementation of specific strategies to prevent progression of OHL, evident through continued high incidence of OHL. This scoping review aimed to identify evidence regarding targeted intervention used by industry, specifically to prevent the progression of OHL for workers. The scoping review was undertaken using the PRISMA-ScR methodology. Search terms were based on three broad categories, hearing loss, workplace, and intervention. Initially 1309 articles were identified for screening and 1,207 studies not meeting the criteria were excluded. Full text reviews of 102 articles were completed and a further 93 studies excluded. The scoping review produced nine studies which were quantitatively analysed. All interventions focused primarily on lower order controls, specifically administrative and personal protective equipment. Eight studies focused on awareness training, health monitoring, mandating hearing protection device use and fit testing, and using personal attenuation ratings as a predictor to OHL. Only one study mentioned isolation of workers from noise sources, and this was an interview study with workplace managers, not a specific intervention at a workplace. The result of the review highlights the lack of published literature on targeted interventions for workers with OHL. There is insufficient evidence to inform effective, impactful change in practice to prevent the progression of OHL. It is recommended that a system of collecting and assessing specific interventions and controls for workers with OHL be developed to better inform industry on strategies that will provide adequate protection for these workers.

Abnormal noise is a key factor affecting automobile ride comfort, and the localisation of abnormal noise sources is critical for noise control. Herein, a mathematical model is proposed for the localisation of automobile door rattle sources based on Lamb wave propagation theory, Morlet wavelet transform, and the principle of time-reversal focus positioning. The cause of vibration signal wave packet aliasing was explored through thin plate impact simulation, and narrow-band signal extraction was then determined. The influence of the initial generation time ({T}_{0}) of the rattle signal on the positioning imaging was obtained through a rattle noise source localisation test, and the signal imaging discrimination method at time ({T}_{0}) was proposed. Verification test results showed that the maximum positioning error of the automobile door rattle noise source was no greater than 3.2 cm, and the average positioning error was 2.01 cm, which confirmed the feasibility of the proposed method for locating the rattle noise source in the automobile door.

Monitoring the condition of divers during immersion is essential to ensuring their safety and planning permissible physical activity. Monitoring respiratory rates using a diver's respiratory sounds as parameters might be used for that purpose. This study was conducted with three types of diving apparatuses intended for civilian use: scuba, closed-circuit, and surface-supplied. Respiratory rates were investigated using wearable acoustic sensors installed in diving suit air cavities or remote hydrophones. The respiratory rate monitoring was also possible using a standard underwater voice communication system. Periodic breathing sounds are distinguishable in open-circuit scuba at a distance of 20 m, and a distance of 100–140 m with additional processing using wavelet transforms. The noise of inhalation and exhalation using closed-circuit breathing apparatus was monitored in the vicinity of the diver's respiratory tract. Respiratory sounds were distinguishable while using surface-supplied diving equipment (diver at the bottom, depth 8 m). The mean respiratory rate was 16.4 respiratory cycles per minute. The researchers could assess a diver's respiratory rate without invasive intervention in the breathing apparatus design. The data obtained were helpful for the remote monitoring of divers by the diving supervisor. Additionally, the data could be entered into a personal decompression computer for self-monitoring.