scholarly journals The Helmholtz resonator for use as a low‐frequency underwater acoustic source

1981 ◽  
Vol 70 (S1) ◽  
pp. S19-S19
Author(s):  
A. M. Young
Keyword(s):  
Low Frequency ◽  
Helmholtz Resonator ◽  
Acoustic Source ◽  
Underwater Acoustic

Tunable underwater acoustic metamaterials via quasi-Helmholtz resonance: From low-frequency to ultra-broadband

2021 ◽  
Vol 118 (7) ◽  
pp. 071904
Author(s):  
Mingyu Duan ◽  
Chenlei Yu ◽  
Fengxian Xin ◽  
Tian Jian Lu
Keyword(s):  
Low Frequency ◽  
Acoustic Metamaterials ◽  
Underwater Acoustic ◽  
Helmholtz Resonance

scholarly journals Design and implementation of a jellyfish otolith-inspired MEMS vector hydrophone for low-frequency detection

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Renxin Wang ◽  
Wei Shen ◽  
Wenjun Zhang ◽  
Jinlong Song ◽  
Nansong Li ◽  
...  
Keyword(s):  
Structural Parameters ◽  
Low Frequency ◽  
Directivity Pattern ◽  
Stress Distributions ◽  
Strong Response ◽  
Underwater Acoustic ◽  
Frequency Detection ◽  
Vector Hydrophone ◽  
Shock Resistance ◽  
Marine Applications

AbstractDetecting low-frequency underwater acoustic signals can be a challenge for marine applications. Inspired by the notably strong response of the auditory organs of pectis jellyfish to ultralow frequencies, a kind of otolith-inspired vector hydrophone (OVH) is developed, enabled by hollow buoyant spheres atop cilia. Full parametric analysis is performed to optimize the cilium structure in order to balance the resonance frequency and sensitivity. After the structural parameters of the OVH are determined, the stress distributions of various vector hydrophones are simulated and analyzed. The shock resistance of the OVH is also investigated. Finally, the OVH is fabricated and calibrated. The receiving sensitivity of the OVH is measured to be as high as −202.1 dB@100 Hz (0 dB@1 V/μPa), and the average equivalent pressure sensitivity over the frequency range of interest of the OVH reaches −173.8 dB when the frequency ranges from 20 to 200 Hz. The 3 dB polar width of the directivity pattern for the OVH is measured as 87°. Moreover, the OVH is demonstrated to operate under 10 MPa hydrostatic pressure. These results show that the OVH is promising in low-frequency underwater acoustic detection.

scholarly journals Acoustic Source Data for Medium Speed IC-Engines

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Antti Hynninen ◽  
Raimo Turunen ◽  
Mats Åbom ◽  
Hans Bodén
Keyword(s):  
High Frequency ◽  
Internal Combustion Engines ◽  
Low Frequency ◽  
Acoustic Source ◽  
Ic Engine ◽  
Source Characteristics ◽  
Medium Speed ◽  
Source Data ◽  
Exhaust Noise ◽  
Ic Engines

Knowledge of the acoustic source characteristics of internal combustion engines (IC-engines) is of great importance when designing the exhaust duct system and its components to withstand the resulting dynamic loads and to reduce the exhaust noise emission. The goal of the present study is to numerically and experimentally investigate the medium speed IC-engine acoustic source characteristics, not only in the plane wave range but also in the high frequency range. The low frequency acoustic source characteristics were predicted by simulating the acoustic multiload measurements by using a one-dimensional process simulation code. The low frequency in-duct exhaust noise of a medium speed IC-engine can be quite accurately predicted. The high frequency source data is estimated by averaging the measured acoustic pressures with different methods; using the simple cross-spectra averaging method seems promising in this instance.

Nonlinear behavior of Helmholtz resonator with a compliant wall for low frequency, broadband noise control

2021 ◽  
pp. 1-29
Author(s):  
Maya Pishvar ◽  
Ryan L Harne
Keyword(s):  
Dynamic Response ◽  
Low Frequency ◽  
Nonlinear Behavior ◽  
Helmholtz Resonator ◽  
Broadband Noise ◽  
Sound Attenuation ◽  
Wall Material ◽  
Modeling Framework ◽  
Compliant Wall ◽  
Broadband Sound

Abstract Low frequency sound attenuation is often pursued using Helmholtz resonators (HRs). The introduction of a compliant wall around the acoustic cavity results in a two-degree-of-freedom (2DOF) system capable of more broadband sound absorption. In this study, we report the amplitude-dependent dynamic response of a compliant walled HR and investigate the effectiveness of wall compliance to improve the absorption of sound in linear and nonlinear regimes. The acoustic-structure interactions between the conventional Helmholtz resonator and the compliant wall result in non-intuitive responses when acted on by nonlinear amplitudes of excitation pressure. This paper formulates and studies a reduced order model to characterize the nonlinear dynamic response of the 2DOF HR with a compliant wall compared to that of a conventional rigid HR. Validated by experimental evidence, the modeling framework facilitates an investigation of strategies to achieve broadband sound attenuation, including by selection of wall material, wall thickness, geometry of the HR, and other parameters readily tuned by system design. The results open up new avenues for the development of efficient acoustic resonators exploiting the deflection of a compliant wall for suppression of extreme noise amplitudes.

Realizing high-efficiency low frequency sound absorption of underwater meta-structures by acoustic siphon effect

2021 ◽  
pp. 2150319
Author(s):  
Li Bo Wang ◽  
Cheng Zhi Ma ◽  
Jiu Hui Wu ◽  
Chong Rui Liu
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
High Efficiency ◽  
Physical Mechanism ◽  
Low Frequency ◽  
Area Ratio ◽  
Underwater Acoustic ◽  
Element Simulation ◽  
Average Absorption Coefficient ◽  
New Perspective

The underwater acoustic siphon effect is proposed in this work, which aims to reveal the basic physical mechanism of high-efficiency sound absorption in meta-structures composed of multiple detuned units. Furthermore, the influence of the area ratio on the underwater acoustic siphon effect is then investigated by finite element simulation (FES) and theoretical calculation. On this basis, a meta-structure with the maximum absorption coefficient of almost 100% and average absorption coefficient of 80% at 600–1400 Hz is achieved. The underwater acoustic siphon effect could provide a better understanding of high-efficiency sound absorption and offer a new perspective in controlling underwater noises.

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