Acoustic characteristics of a sound field inside a cylindrical structure with excited end plates: Influence of excitation position on vibro-acoustic coupling

The vibrational behavior of an underwater structure in the free field is different from that in bounded noisy environments because the fluid–structure interaction is strong in the water and the vibration of the structure caused by disturbing fields (the reflections by boundaries and the fields radiated by sources of disturbances) cannot be ignored. The conventional free field recovery (FFR) technique can only be used to eliminate disturbing fields without considering the difference in the vibrational behavior of the structure in the free field and the complex environment. To recover the free-field acoustic characteristics of a structure from bounded noisy underwater environments, a method combining the boundary element method (BEM) with the vibro-acoustic coupling method is presented. First, the pressures on the measurement surface are obtained. Second, the outgoing sound field and the rigid body scattered sound field are calculated by BEM. Then, the vibro-acoustic coupling method is employed to calculate the elastically radiated scattered sound field. Finally, the sound field radiated by the structure in the free field is recovered by subtracting the rigid body scattered sound field and the elastically radiated scattered sound field from the outgoing sound field. The effectiveness of the proposed method is validated by simulation results.

Download Full-text

Study on acoustic and flow-induced noise characteristics of L-shaped duct with a shallow cavity

Noise Control Engineering Journal ◽

10.3397/1/376818 ◽

2020 ◽

Vol 68 (3) ◽

pp. 209-225

Author(s):

Masaaki Mori ◽

Kunihiko Ishihara

Keyword(s):

Air Conditioning ◽

Sound Field ◽

Frequency Range ◽

Acoustic Characteristics ◽

Inflow Velocity ◽

Aerodynamic Sound ◽

Noise Characteristics ◽

Flow Induced Noise ◽

Shallow Cavity ◽

Conditioning Equipment

An aerodynamic sound generated by a flow inside a duct is one of the noise pro- blems. Flows in ducts with uneven surfaces such as grooves or cavities can be seen in various industrial devices and industrial products such as air-conditioning equipment in various plants or piping products. In this article, we have performed experiments and simulations to clarify acoustic and flow-induced sound characteris- tics of L-shaped duct with a shallow cavity installed. The experiments and simula- tions were performed under several inflow velocity conditions. The results show that the characteristics of the flow-induced sound in the duct are strongly affected by the acoustic characteristics of the duct interior sound field and the location of the shallow cavity. Especially, it was found that the acoustic characteristics were af- fected by the location of the shallow cavity in the frequency range between 1000 Hz and 1700 Hz.

Download Full-text

Design and Construction of a Small Reverberation Chamber Applied to Absorption and Scattering Acoustic Measurements

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1077.197 ◽

2014 ◽

Vol 1077 ◽

pp. 197-202

Author(s):

D. Hernandez ◽

E.J. Liu ◽

J.H. Huang ◽

Y.C. Liu

Keyword(s):

High Frequency ◽

Integration Method ◽

Sound Field ◽

Acoustic Measurements ◽

Acoustic Characteristics ◽

Reverberation Chamber ◽

Scattering Coefficients ◽

Reverberation Chambers ◽

The Cost ◽

Design And Construction

Reverberation chambers are used to create a diffuse incidence sound field, where multiple types of acoustic measurements can be performed. The chambers tend to have a large volume in order to extent the reverberation time. However, this requirement may be conditioned by the cost and the infrastructure limitations. This paper presents the design and construction of a small-scaled reverberation chamber of 3 m3 for middle-high frequency acoustic measurements. On the design, the acoustic characteristics of chamber are confirmed via finite element computer simulation. As case studies, absorption and scattering coefficients of several materials and diffusors are measured. The reverberation times needed for the measurements were obtained by the impulse response integration method. The small reverberation chamber demonstrated to be a reliable tool for middle and high frequency acoustic measurements.

Download Full-text

EFFICIENT ACOUSTIC COMPOSITE PANELS BASED ON GRAPHITE

Bulletin of Belgorod State Technological University named after V G Shukhov ◽

10.34031/2071-7318-2021-6-4-82-90 ◽

2021 ◽

Vol 6 (4) ◽

pp. 82-90

Author(s):

E. Fanina

Keyword(s):

Experimental Studies ◽

Three Dimensional ◽

Sound Field ◽

Fire Retardant ◽

Pyramidal Cells ◽

Sound Insulation ◽

Composite Panels ◽

Thin Membrane ◽

Reverberation Time ◽

Acoustic Characteristics

A set of experimental studies is carried out to determine the acoustic characteristics of three-dimensional panels of fixed thickness made of carbon-based composite material installed in the opening between the reverberation chambers. Sound insulation indices are determined when they are excited by a diffuse sound field in wide frequency ranges. The reverberation time in model chambers with different partition configurations is calculated. The optimal configuration of the partition with pyramidal cells to reduce the reverberation time in the rooms is determined. The use of graphite in the form of thin membrane applied to various surfaces can significantly reduce the sound pressure levels in the room and increase the sound insulation indices of air noise. In addition to thin membrane, graphite can be used as an additive in composite materials for sound insulation purposes. It is shown that the characteristics of such panels are quite universal. The measured acoustic characteristics of composite panels are compared with similar characteristics of traditional materials. It is determined that the composition belongs to the I group of fire-retardant efficiency and can be recommended for use as a fire-retardant material. The developed acoustic material is an effective absorbing agent that solves problems in architectural acoustics, echo cancellation in construction and architecture. Similar to metamaterials, natural and artificial graphites allow to solve these problems with small volumes and masses using simple and inexpensive technologies.

Download Full-text

Investigation of turbulence-induced quadrupole source acoustic characteristics of a three-dimensional hydrofoil

Modern Physics Letters B ◽

10.1142/s0217984920501456 ◽

2020 ◽

Vol 34 (14) ◽

pp. 2050145

Author(s):

Rennian Li ◽

Wenna Liang ◽

Wei Han ◽

Hui Quan ◽

Rong Guo ◽

...

Keyword(s):

Vortex Shedding ◽

Sound Pressure Level ◽

Sound Pressure ◽

Three Dimensional ◽

Sound Field ◽

Leading Edge ◽

Pressure Level ◽

Acoustic Characteristics ◽

Eddy Simulation ◽

Unsteady Fluid

In order to investigate the turbulence-induced acoustic characteristics of hydrofoils, the flow and sound field for a model NH-15-18-1 asymmetric hydrofoil were calculated based on the mixed method of large eddy simulation (LES) with Lighthill analogy theory. Unsteady fluid turbulent stress source around the hydrofoil were selected as the inducements of quadrupole sound. The average velocity along the mainstream direction was calculated for different Reynolds numbers [Formula: see text]. Compared to experimental measurements, good agreement was seen over a range of [Formula: see text]. The results showed that the larger the [Formula: see text], the larger the vortex intensity, the shorter the vortex initial shedding position to the leading edge of the hydrofoil, and the higher the vortex shedding frequency [Formula: see text]. The maximum sound pressure level (SPL) of the hydrofoil was located at the trailing edge and wake of the hydrofoil, which coincided with the velocity curl [Formula: see text] distribution of the flow field. The maximum SPL of the sound field was consistent with the location of the vortex shedding. There were quadratic positive correlations between the total sound pressure level (TSPL) and the maximum value of the vortex intensity [Formula: see text] and velocity curl, which verified that shedding and diffusion of vortices are the fundamental cause of the generation of the quadrupole source noise.

Download Full-text

432 Acoustic Characteristics in a Cylindrical Structure with End Plates under Elastic Edge Supports

The Proceedings of Yamanashi District Conference ◽

10.1299/jsmeyamanashi.2000.127 ◽

2000 ◽

Vol 2000 (0) ◽

pp. 127-128

Author(s):

Hiroyuki MORIYAMA ◽

Yoshiaki YASUI

Keyword(s):

Acoustic Characteristics ◽

Cylindrical Structure ◽

Elastic Edge

Download Full-text

Energy Harvesting with Piezoelectric Element Using Vibroacoustic Coupling Phenomenon

Advances in Acoustics and Vibration ◽

10.1155/2013/126035 ◽

2013 ◽

Vol 2013 ◽

pp. 1-11 ◽

Cited By ~ 1

Author(s):

Hiroyuki Moriyama ◽

Hirotarou Tsuchiya ◽

Yasuo Oshinoya

Keyword(s):

Energy Harvesting ◽

Electric Energy ◽

Piezoelectric Element ◽

Sound Field ◽

Structural Vibrations ◽

Acoustic Characteristics ◽

Sound Fields ◽

Plate Vibrations ◽

Cylinder Length ◽

Experimental Apparatus

This paper describes the vibroacoustic coupling between the structural vibrations and internal sound fields of thin structures. In this study, a cylindrical structure with thin end plates is subjected to the harmonic point force at one end plate or both end plates, and a natural frequency of the end plates is selected as the forcing frequency. The resulting vibroacoustic coupling is then analyzed theoretically and experimentally by considering the dynamic behavior of the plates and the acoustic characteristics of the internal sound field as a function of the cylinder length. The length and phase difference between the plate vibrations, which maximize the sound pressure level inside the cavity, are clarified theoretically. The theoretical results are validated experimentally through an excitation experiment using an experimental apparatus that emulates the analytical model. Moreover, the electricity generation experiment verifies that sufficient vibroacoustic coupling can be created for the adopted electricity generating system to be effective as an electric energy-harvesting device.

Download Full-text