  This paper presents an active noise control experiment designed to validate a
real-time control strategy for reduction of the noise scattered from a
three-dimensional body. The control algorithm relies on estimating the
scattered noise by linear filtering of the total noise measured around the
body; suitable filters are identified from off-line measurements. A modified
Filtered-Error Least-Mean-Squares algorithm then leads to the adaptive filters
which drive the secondary sources. The paper provides the numerical simulations
using a Boundary Element Method which helped in designing a feasible experiment
in an anechoic chamber with a limited number of control sources. Eventually a
real-time pure-tone implementation with 14 ordinary loudspeakers and a large
body is shown to yield on average a 10 dB reduction of the scattered noise at
the error sensors, which is close to the optimum reduction predicted by the
numerical simulations for the sensor arrangement.

Classical Physics