Ws. Shepard et Ka. Cunefare, ACTIVE CONTROL OF EXTENDED ACOUSTIC SOURCES IN A HALF-SPACE, The Journal of the Acoustical Society of America, 96(4), 1994, pp. 2262-2271
Many noise sources, such as an electronic transformer, are located on
or near an acoustically rigid planar surface, such as a concrete floor
. Thus far, however, most of the active noise control research has bee
n based on the free-field assumption. The work presented here investig
ates the effect the presence of a rigid plane has on the active noise
control of an acoustic source with characteristic dimensions comparabl
e to the acoustic wavelength at the frequency of interest. It is shown
that when the source is located a distance of one wavelength or more
from the plane, the presence of the plane may be neglected. However, t
he minimum radiated power computed using a free space active analysis
can be significantly greater than that predicted using a half space ac
tive analysis for distances less than one wavelength. As a result, usi
ng the simpler free space analysis techniques leads to less effective
control for distances less than one wavelength.