Appeal No. 1998-2675
Application 08/779,024
largest dimension is smaller than the wavelength of the
highest frequency of the primary vibration to be nulled and
locating the microphone in the volume (col. 2, lines 18-24).
By enclosing the microphone and driver in a relatively small
volume, the near field of the driver becomes much more
uniform, the microphone is isolated from nearby reflecting
surfaces, and the efficiency to null primary vibrations is
increased (col. 2, lines 35-43). The primary vibrations to be
canceled can be fed directly into the partially closed small
volume or the primary vibrations can be sensed by a microphone
upstream of the small volume, the output of the microphone
being fed to the loop of the virtual earth system (col. 2,
lines 44-52). Chaplin discloses that gas permeable thermal
insulation can be included in the small volume 4" of figure 6
or surrounding the perforated pipe in figure 7 to protect the
drivers and microphone from the heat of an engine.
Initially, we find that the purpose of the enlarged room
in Chaplin is to make the pressure from the driver more
uniform around the microphone, not to protect the microphone
under extreme temperature conditions, as found by the
Examiner; it is the thermal insulation included in the volume
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