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US 5,748,749 AGranted
Active noise cancelling muffler
AssigneeNoise Cancellation Technologies, Inc.
InventorsScott Miller, J. Clay Shipps
Life of this patent
Estimating the term…
Abstract
An active muffler noise cancellation system having an active controller, a speaker housing with acoustic compliance spaces, a duct extension in communication with said speaker housing and adapted to conform a dipole radiation pattern into a plane wave which can be measured by a microphone.
Claims13
An active noise canceling muffler system for use on stationary or vehicle applications which involve an exhaust pipe, said system comprising:
- an active noise enclosure:
- an active noise attenuator in said active enclosure adapted to produce a counter noise wave to cause destructive interference with a noise wave emanating from said exhaust pipe;
- an adaptive controller connected to said active noise attenuator;
- an extension duct connected to said active enclosure through a port and adapted to receive a terminus of said exhaust pipe so as to receive both said exhaust pipe gases, said noise and said counter noise at one end of said extension duct, said noise and counter noise combining to form a single plane wave at an opposite end of said extension duct;
- and
- a transducer listening device on said extension duct and adapted to provide a residual signal to said adaptive controller to allow it to adjust said active noise attenuator to provide the necessary counter noise,
- wherein a dipole is created where the noise and counter noise enter said duct extension, the shape of said duct extension forcing said dipole pattern into a plane wave adjacent said transducer listening device.
4 more elements
An active noise canceling muffler system for use on stationary or vehicle applications which involve an exhaust pipe, said system comprising:
- an active noise enclosure;
- an active noise attenuator in said active enclosure adapted to produce a counter noise wave to cause destructive interference with a noise wave emanating from said exhaust pipe;
- an adaptive controller connected to said active noise attenuator;
- an extension duct connected to said active enclosure through a port and adapted to receive a terminus of said exhaust pipe so as to receive both said exhaust pipe gases, said noise and said counter noise at one end of said extension duct, said noise and counter noise combining to form a single plane wave at an opposite end of said extension duct;
- and
- a transducer listening device on said extension duct and adapted to provide a residual signal to said adaptive controller to allow it to adjust said active noise attenuator to provide the necessary counter noise,
- wherein the length of the extension duct is larger than the smallest cross section dimension, but less than one fourth of a wavelength of sound at the maximum frequency controlled.
4 more elements
Dependencies are inferred from the claim text.