Appeal No. 1998-2675
Application 08/779,024
This is a decision on appeal under 35 U.S.C. § 134 from
the final rejection of claims 1, 3-5, and 8-11.
We reverse.
BACKGROUND
The invention is directed to a configuration in which a
microphone is attached inside a duct for use in active noise
reduction systems. A problem in active noise reduction
systems is that the microphone provided in a duct picks up
noise generated by the current of air which cannot be
adequately suppressed by acoustic insulation. This noise
consists of sounds made by the friction of air with the
microphone and by the shaking movement of the microphone blown
by an air current. Appellants' solution is to increase the
cross sectional area of the duct, which reduces the velocity
of the air current and, hence, the effect of the air current
on the microphone.
Claim 1 is reproduced below.
1. A configuration of providing a microphone in a
duct having an air current therein, for use in an active
noise reduction device having said microphone pick up
noise propagating in said duct, having a speaker
producing sounds counteracting said noise, and having an
auxiliary microphone provided downstream from said
microphone for picking up remnant noise, said speaker and
said auxiliary microphone forming a closed loop for
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