0
TECHNICAL PAPERS

Reconstruction and Separation in a Semi-Free Field by Using the Distributed Source Boundary Point Method-Based Nearfield Acoustic Holography

[+] Author and Article Information
C. X. Bi

Institute of Sound and Vibration Research, Hefei University of Technology, Hefei 230009, P R Chinacxbi@hfut.edu.cn

X. Z. Chen, R. Zhou, J. Chen

Institute of Sound and Vibration Research, Hefei University of Technology, Hefei 230009, P R China

J. Vib. Acoust 129(3), 323-329 (Jan 11, 2007) (7 pages) doi:10.1115/1.2731403 History: Received January 10, 2006; Revised January 11, 2007

In a semi-free field, the acoustic field is composed of two components: the direct sound and the reflected sound. Because it is difficult to separate the direct sound from the acoustic field, conventional nearfield acoustic holography (NAH) methods cannot reconstruct an acoustic source and predict the acoustic field directly. Through utilization of the distributed source boundary point method (DSBPM)-based NAH, a treatment method for a semi-free field is proposed. In the method, the source in a semi-free field can be reconstructed correctly, and the acoustic field can be predicted and separated. An experiment on a speaker in a semi-anechoic chamber is carried out to verify the proposed method. By comparing the reconstructed and predicted results in DSBPM-based NAH with and without the proposed method, the proposed method is validated. The disadvantages of NAH without any treatment method in a semi-free field are demonstrated.

FIGURES IN THIS ARTICLE
<>
Copyright © 2007 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

Definition of the geometric condition of the source in the infinite domain

Grahic Jump Location
Figure 2

The particular solution sources located inside the vibrating structure

Grahic Jump Location
Figure 3

Image method for acoustic radiation from a vibrating structure in a semi-free field

Grahic Jump Location
Figure 4

Photograph of experimental devices

Grahic Jump Location
Figure 5

Node distribution on the speaker

Grahic Jump Location
Figure 6

Amplitude distributions of the reconstructed surface normal velocities of the speaker in the two methods: (a) Without the proposed method and (b) with the proposed method

Grahic Jump Location
Figure 7

The predicted z-direction active acoustic intensities on the surface located 0.1m away from the front surface of the speaker in the two methods: (a) Without the proposed method and (b) with the proposed method

Grahic Jump Location
Figure 8

Comparisons of the predicted pressures and their measured values at some points in the region {x=0,−0.1m≤y≤0.1m,−0.1m≤z≤0.15m}: (a) The amplitude comparisons and (b) the predicted errors, where ◻ denotes the values without the proposed method, + denotes the values with the proposed method, and 엯 denotes the measured values

Grahic Jump Location
Figure 9

The amplitude percent of the reflected pressure in the total pressure on the surface located 0.1m away from the front face of the speaker

Grahic Jump Location
Figure 10

The predicted normal active acoustic intensities on the predicted surface located 0.88m away from the front face of the speaker in the two methods: (a) Without the proposed method and (b) with the proposed method

Grahic Jump Location
Figure 11

The amplitude percent of the reflected pressure in the total pressure on the predicted surface located 0.88m away from the front face of the speaker

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In