ENGINEERING ANALYSIS INC.
ACTIVE NOISE CONTROL
The study has involved fractional calculus
applied to active broad-band noise control. Noise processes with regular
or rational spectra can be adequately modeled by common distributions and
linear filters. Noise processes, however, are often characterized by
irregular or non-rational spectra. The large number of coefficients
associated with the filter transfer functions for these processes results
from the use of rational approximation techniques. By fractional calculus
techniques such noise processes can be described with significantly fewer
coefficients. In the adaptive filter design, with fewer coefficients to
handle, the search algorithm can be accelerated. An adaptive filter
design based on fractional calculus was developed for active noise
control. A numerical procedure based on the Grunwald relation was
developed for solving the governing fractional differential equation for
generating the antinoise of a class of noise processes with only one
spectral peak. The residual noise was minimized by the method of steepest
descent. Based on such procedures the ANFRAC
program was developed. The study demonstrates that an adaptive filter
based on fractional calculus for active broad-band noise control is
clearly feasible.
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