• 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

Nov 1999

Volume 106, Issue 5, pp. 2321-L52

Return to All Sections
back to top
RSS Feeds

A broadband passive–active sound absorption system

Jerome P. Smith, Brody D. Johnson, and Ricardo A. Burdisso

J. Acoust. Soc. Am. Volume 106, Issue 5, pp. 2646-2652 (1999); (7 pages) | Cited 8 times

Full Text: | Download PDF

Show Abstract
In recent years, hybrid absorption systems have been implemented which achieve high sound absorption over a broad frequency range. This work is an experimental study of a broadband hybrid absorption system which is comprised of a layer of sound-absorbing material (the passive component) positioned at a distance from a movable wall (the active component) inside an impedance tube. The movable wall is used to impose desired boundary conditions in the cavity behind the passive layer, thereby increasing the absorption of the system at frequencies where the passive material is not independently effective. Both pressure-release (i.e., minimizing the pressure at the back surface of the layer) and impedance-matching (i.e., minimizing the reflected wave from the layer) boundary conditions are studied. The performance of the hybrid system for these two boundary conditions is compared for broadband disturbances over a frequency range of 100–1000 Hz. The unmodified passive system showed absorption coefficients greater than 0.7 only above 500 Hz, while the impedance-matching condition yielded absorption coefficients of 0.8 to 1.0 over the 100–1000-Hz range. The impedance-matching condition provided significantly better absorption than that achieved with the pressure-release condition. The sensitivity of these control approaches to system parameters is also investigated. © 1999 Acoustical Society of America.
Show PACS
43.55.Ev Sound absorption properties of materials: theory and measurement of sound absorption coefficients; acoustic impedance and admittance
Return to All Sections
Close

Home Publications Meetings Contact ASA Site Map Back to Top

Copyright © Acoustical Society of America

close