U-009
Experimental characterization of the near field zones of silence in an active sound cancellation scheme
Authors: A. B. Wright, A. Karthikeyan
Affiliation: University of Arkansas at Little Rock, Department of Applied Science
Abstract
A filtered X-LMS active sound cancellation (ASC) scheme consisting of a primary source,
a secondary source, and an error microphone was used to experimentally determine
the near field destructive interference patterns. The patterns for single tones of
80 and 125 Hz were mapped, and the patterns for an additive combination of 80 Hz
and 125 Hz were mapped. The interference patterns for a measurement plane, parallel
to the support surface and centered on the error microphone, were determined. The
plane was discretized radially and circumferentially, and the average sound pressure
level (SPL) was determined at each point. Level curves were generated to provide
a comparison between SPLs in the near field both with the primary source acting alone
and with the destructive interference generated by ASC. The primary field was substantially
reduced in the entire region beyond the error microphone and away from the primary
source. Although the magnitude of reduction for each of the primary source waveforms
was different, the general interference pattern that occurs for an ASC system was
similar.
Dr. Andrew B. Wright
University of Arkansas at Little Rock
Department of Applied Science
2801 South University, Little Rock, AR 72204
abwright@ualr.edu