Active acoustic noise reduction technique
OwnerYin-Hua Chiainventor
Life of this patent
Estimating the term…
Abstract
An acoustical noise reduction system which comprises a primary acoustic to electric transducer, digital signal processor (DSP), an electric to acoustic transducer, and a secondary acoustic to electric transducer is disclosed in the present invention. The active noise reduction system is located close to the noise source with the sound being sensed by a primary transducer before the noise enters the active noise reduction area. The system functions to generate an anti-noise cancellation sound wave with an acoustic propagation speed of approximately 330 m/sec and an electromagnetic propagation speed of approximately 3×10̂8 m/sec.
Claims6
An active acoustic noise reduction system for reducing the effects of a noise source, comprising:
- at least one sound source means provided in a sound field,
- at least one primary sensing means such as a primary transducer provided in the sound field for sensing the sound source and providing an input signal corresponding to sound from the sound source means and noise in the sound field,
- at least one anti-aliasing filter,
- at least one analog-to-digital converter,
- at least one digital-to-analog converter,
- at least one dual port RAM that is large enough to store at least a few seconds worth of noise samples,
- at least one MIC1 sampling storage,
- at least one match filter,
- at least one secondary sensing means such as a secondary transducer provided in the sound field for sensing the sound source and providing an input signal corresponding to sound from the sound source means and noise in the sound field,
- at least one MIC2 sampling storage,
- at least one gain ratio estimator,
- at least one gain setting device,
- wherein the MIC1 sampling storage scans through the dual port RAM and feeds into a match filter,
- wherein the MIC2 sampling storage stores a fixed amount of converted noise samples in digital format and feeds into a match filter,
- wherein the match filter synchronizes the stored sampled gathered in the primary sensing means to the truncated signal from the secondary sensing means,
- wherein the gain ratio estimator compares the gain of the output of the dual port RAM and the gain of the output of the MIC2 sample storage and feeds the ratio into the gain setting device to drive the transducer,
- wherein the transducer converts electrical energy into acoustic energy with inverted polarity,
- wherein ratio is applied to the acoustic output of the dual port RAM before entering into the digital-to-analog converter.
Dependencies are inferred from the claim text.