• Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Journal of the Acoustical Society of America

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

Apr 2006

Volume 119, Issue 4, pp. 1897-EL59

Return to All Sections
back to top
RSS Feeds

Acoustic pulse propagation near a right-angle wall

Lanbo Liu and Donald G. Albert

J. Acoust. Soc. Am. Volume 119, Issue 4, pp. 2073-2083 (2006); (11 pages) | Cited 14 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Experimental measurements were conducted around a right-angle wall to investigate the effect of this obstacle on sound propagation outdoors. Using small explosions as the source of the acoustic waves allowed reflected and diffracted arrivals to be discerned and investigated in detail. The measurements confirm that diffraction acts as a low-pass filter on acoustic waveforms in agreement with simple diffraction theory, reducing the peak pressure and broadening the waveform shape received by a sensor in the shadow zone. In addition, sensors mounted directly on the wall registered pressure doubling for nongrazing angles of incidence in line-of-sight conditions. A fast two-dimensional finite difference time domain (FDTD) model was developed and provided additional insight into the propagation around the wall. Calculated waveforms show good agreement with the measured waveforms.
Show PACS
43.28.En Interaction of sound with ground surfaces, ground cover and topography, acoustic impedance of outdoor surfaces
43.28.Js Numerical models for outdoor propagation
43.20.El Reflection, refraction, diffraction of acoustic waves
43.50.Vt Topographical and meteorological factors in noise propagation

Sound generated by vortices in the presence of a porous half-cylinder mounted on a rigid plane

C. K. Lau and S. K. Tang

J. Acoust. Soc. Am. Volume 119, Issue 4, pp. 2084-2095 (2006); (12 pages) | Cited 3 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The sound generated by a single vortex and by two identical vortices in the presence of a half-cylinder made of porous material mounted on a rigid horizontal plane is studied theoretically using the acoustic analogy and the matched asymptotic expansion method. Both longitudinal and transverse dipoles are observed upon the introduction of the porous cylinder, but the former is considerably stronger than the latter in all the cases studied. Results suggest that the amplitudes of the dipoles and the overall acoustical energy radiated can be higher than that in the rigid cylinder case under some suitable combinations of flow parameters, especially when the flow resistance inside the porous material seen by the vortices is very small.
Show PACS
43.28.Ra Generation of sound by fluid flow, aerodynamic sound and turbulence
43.50.Nm Aerodynamic and jet noise
43.50.Gf Noise control at source: redesign, application of absorptive materials and reactive elements, mufflers, noise silencers, noise barriers, and attenuators, etc.
Return to All Sections
Close

Home Publications Meetings Contact ASA Site Map Back to Top

Copyright © Acoustical Society of America

close