A local active noise control system is described which uses a virtual microphone arrangement. This arrangement is based on the assumption that the primary pressure at the physical and at the virtual microphone locations are similar. The implication of this assumption on the acoustic performance of a local system in a diffracted primary sound field is theoretically studied. The results show that the error at the virtual microphone position is lower when the virtual microphone arrangement is in the vicinity of a diffracting surface. A practical local active noise control system in a headrest has been built and used to measure the zone of quiet produced by a single and a dual channel system when the total pressure is canceled at one or two virtual microphone positions. It is shown that this type of arrangement is capable of projecting the zones of quiet further away from the secondary source than the position of the physical microphone. The measured zones of quiet produced by a single-channel system have bee...
[1]
R. M. Sachs,et al.
Anthropometric manikin for acoustic research.
,
1975,
The Journal of the Acoustical Society of America.
[2]
Philip A. Nelson,et al.
Active cancellation at a point in a pure tone diffuse sound field
,
1988
.
[3]
Stephen J. Elliott,et al.
ACTIVE CANCELLATION OF PRESSURE AT A POINT IN A PURE TONE DIFFRACTED DIFFUSE SOUND FIELD
,
1997
.
[4]
S. Elliott,et al.
Numerical studies of actively generated quiet zones
,
1994
.
[5]
Francis M. Wiener,et al.
The Pressure Distribution in the Auditory Canal in a Progressive Sound Field
,
1946
.
[6]
S. J. Elliott,et al.
Local active control of diffracted diffuse sound fields
,
1995
.
[7]
S. Elliott,et al.
Near Field Zones of Quiet
,
1994
.