Low-frequency sound field in a room with a Helmholtz resonator

2000 ◽  
Vol 46 (4) ◽  
pp. 491-493 ◽  
Author(s):  
A. D. Lapin
Keyword(s):  
Low Frequency ◽  
Sound Field ◽  
Helmholtz Resonator ◽  
Frequency Sound

Low Frequency Sound as a Navigational Tool for People with Visual Impairments

2002 ◽  
Vol 21 (4) ◽  
pp. 199-205 ◽  
Author(s):  
Daniel Ashmead ◽  
Robert Wall
Keyword(s):  
Wall Motion ◽  
Visual Impairments ◽  
Low Frequency ◽  
Sound Field ◽  
Frequency Sound ◽  
Acoustic Information ◽  
Large Structures ◽  
Dominant Feature ◽  
Mistaken Assumption ◽  
Navigational Tool

For decades, a mistaken assumption in the habilitation of travel for people with visual impairments has been that the use of “echolocation” is a dominant feature of acoustic information for the guidance of locomotion. This paper outlines a theoretical model of acoustic information available in many travel situations. The acoustic information consists of a build up of low frequency sound along large structures such as walls. Useful frequencies are low enough that the experience of this build up is often one of feeling rather than hearing. Experimental validation of this model was accomplished by having participants with visual impairments walk along walls with varying types of auditory occlusion and through laboratory based manipulations of acoustic information. Results indicate that the model is appropriate. Useful acoustic information appears to extend up to 1 m from a wall. There is strong evidence that participants make use of binaural information, gauging the similarity of acoustic information reaching each ear to maintain orientation to a wall. Motion through the sound field near the wall makes the information more useful but it is unclear whether motion in certain directions or conditions is more useful than others.

A simple acoustic model to characterize the internal low frequency sound field in centrifugal pumps

2011 ◽  
Vol 72 (1) ◽  
pp. 59-64 ◽  
Author(s):  
Jorge Parrondo ◽  
Javier Pérez ◽  
Raúl Barrio ◽  
José González
Keyword(s):  
Low Frequency ◽  
Sound Field ◽  
Acoustic Model ◽  
Centrifugal Pumps ◽  
Frequency Sound

Active Control of Low-Frequency Sound Radiation From Vibrating Panel Using Planar Sound Sources

2001 ◽  
Vol 124 (1) ◽  
pp. 2-9 ◽  
Author(s):  
Kean Chen ◽  
Gary H. Koopmann
Keyword(s):  
Active Control ◽  
Near Field ◽  
Low Frequency ◽  
Sound Radiation ◽  
Sound Field ◽  
Sound Power ◽  
Frequency Range ◽  
Sound Sources ◽  
Frequency Sound ◽  
Secondary Sources

Active control of low frequency sound radiation using planar secondary sources is theoretically investigated in this paper. The primary sound field originates from a vibrating panel and the planar sources are modeled as simply supported rectangular panels in an infinite baffle. The sound power of the primary and secondary panels are calculated using a near field approach, and then a series of formulas are derived to obtain the optimum reduction in sound power based on minimization of the total radiate sound power. Finally, active reduction for a number of secondary panel arrangements is examined and it is concluded that when the modal distribution of the secondary panel does not coincide with that of the primary panel, one secondary panel is sufficient. Otherwise four secondary panels can guarantee considerable reduction in sound power over entire frequency range of interest.

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