Active noise control system

• US 5,359,662 A
• Filed: 04/29/1992
• Issued: 10/25/1994
• Est. Priority Date: 04/29/1992
• Status: Expired due to Fees

• Current Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Kapsokavathis, Nick S., Kuo, Sen M., Chen, Ke, Yuan, Yi
• Primary Examiner(s): Isen, Forester W.
• Application Number:
  US07/875,775
• Time in Patent Office: 909 Days
• Field of Search: 381/71, 381/94
• US Class Current: 381/71.14
• CPC Class Codes: G10K 11/17823 Reference signals, e.g. ambient acoustic environment
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17855 for improving speed or power requirements
• CPC Class Codes: G10K 11/17883 the reference signal being derived from a machine operating condition, e.g. engine RPM or vehicle speed
• CPC Class Codes: G10K 2210/1282 Automobiles
• CPC Class Codes: G10K 2210/3032 Harmonics or sub-harmonics
• CPC Class Codes: G10K 2210/3039 Nonlinear, e.g. clipping, numerical truncation, thresholding or variable input and output gain
• CPC Class Codes: G10K 2210/3042 Parallel processing
• CPC Class Codes: G10K 2210/3046 Multiple acoustic inputs, multiple acoustic outputs
• CPC Class Codes: G10K 2210/3211 Active mounts for vibrating structures with means to actively suppress the vibration, e.g. for vehicles
• CPC Class Codes: G10K 2210/3212 Actuator details, e.g. composition or microstructure
• CPC Class Codes: G10K 2210/511 Narrow band, e.g. implementations for single frequency cancellation

Abstract

A active noise control system is described for attenuating an undesirable noise that containing multiple noise components having different frequencies. The system includes a configuration of signal generators and corresponding paired adaptive filters. Each signal generator produces a generator output signal containing one or more sinusoidal signal components, with each signal component having a frequency corresponding to a respective one of the noise frequency components. Separate signal generators are used to produce those sinusoidal components having frequencies corresponding to noise component that are adjacent with respect to their frequencies. Each adaptive filter operates on the generator output signal produced by its corresponding paired signal generator in accordance with its filtering characteristics to provide a respective filtered output signal. The filtered output signals from each adaptive filter are summed to obtain an output canceling signal, which drives an actuator to produce output canceling waves that are superpositioned with the undesirable noise. An error sensor measures the level of residual noise resulting from the superposition of the canceling waves and the undesirable noise, and provides an error signal for adapting the characteristics of the adaptive filters so as to minimize the level of residual noise.

Claims

1. A system for attenuating undesirable noise produced by a noise source, wherein the undesirable noise contains multiple sinusoidal noise components each having a different frequency, the system comprising:

signal generating means for producing a plurality of generator output signals, each generator output signal containing at least one sinusoidal signal component varying at a frequency corresponding to that of a respective one of the multiple noise components, wherein signal components varying at frequencies corresponding to those of noise components that are adjacent with respect to frequency are contained in different ones of the generator output signals and at least one of the plurality of generator output signals contains at least two sinusoidal signal components;

a plurality of adaptive filters, each adaptive filter operating to filter a respective one of the generator output signals to produce a corresponding filter output signal in accordance with filtering characteristics of the adaptive filter;

summing means for adding each filter output signal to produce an output canceling signal;

means for generating noise canceling waves in response to the output canceling signal and for superimposing the canceling waves with the undesirable noise, whereby the undesirable noise is attenuated;

means for sensing a residual noise level resulting from the superposition of the canceling waves and the undesirable noise and for developing an error signal indicative of the residual noise level; and

means for adaptively adjusting the filtering characteristics of each one of the adaptive filters in accordance with the error signal to reduce the sensed level of residual noise.

2. A system for attenuating undesirable noise produced by a noise source, wherein the undesirable noise contains multiple sinusoidal noise components each having a different frequency, the system comprising:

means for deriving a reference input signal having a value that is functionally related to the frequency of each of multiple noise components contained in the undesirable noise;

a plurality of signal generators each producing a respective signal generator output signal in response to the reference input signal value, and each generator output signal contains at least one sinusoidal signal component varying at a frequency corresponding to that of a respective one of the multiple noise components, wherein signal component varying at frequencies corresponding to those of noise components that are adjacent with respect to frequency are contained in different ones of the generator output signals and at least one of the plurality of generator output signals contains at least two sinusoidal signal components and each generator output signal is derived from a respective predetermined schedule of values based upon the reference input signal value, with the values in the respective predetermined schedule being obtained from a summation containing at least one sinusoidal term having an argument related to an integer multiple of the reference input signal value;

a plurality of adaptive filters, each adaptive filter operating to filter a respective one of the generator output signals to produce a corresponding filter output signal in accordance with filtering characteristics of the adaptive filter;

summing means for adding each filter output signal to produce an output canceling signal;

means for generating noise canceling waves in response to the output canceling signal and for superimposing the canceling waves with the undesirable noise, whereby the undesirable noise is attenuated;

means for sensing a residual noise level resulting from the superposition of the canceling waves and the undesirable noise and for developing an error signal indicative of the residual noise level; and

means for adaptively adjusting the filtering characteristics of each one of the adaptive filters in accordance with the error signal to reduce the sensed level of residual noise.

3. A system for attenuating undesirable noise generated by an internal combustion engine, wherein the undesirable noise contains multiple sinusoidal noise components each having a different frequency related to the time rate of change of the angular rotational position of the engine in its operating cycle, the system comprising:

means for sensing the angular rotational position of the engine in its operating cycle;

a plurality of signal generators each producing a respective generator output signal in response to the sensed rotational position of the engine in its operating cycle, each generator output signal containing at least one sinusoidal signal component varying at a frequency corresponding to the frequency of a respective one of the multiple noise components, wherein sinusoidal signal components varying at frequencies corresponding to those of noise components that are adjacent with respect their frequencies are produced by different ones of the signal generators and at least one of the plurality of generator output signals contains at least two sinusoidal signal components;

a plurality of adaptive filters, each adaptive filter operating to filter a respective one of the generator output signals to produce a corresponding filter output signal in accordance with filtering characteristics of the adaptive filter;

summing means for adding each filter output signal to produce an output canceling signal;

means for generating noise canceling waves in response to the output canceling signal and for superimposing the canceling waves with the undesirable noise, whereby the undesirable noise is attenuated;

means for sensing a residual noise level resulting from the superposition of the canceling waves and the undesirable noise and for developing an error signal indicative of the residual noise level; and

means for adaptively adjusting the filtering characteristics of each one of the adaptive filters in accordance with the error signal to reduce the sensed level of residual noise.