Active adaptive noise canceller without training mode

• US 5,117,401 A
• Filed: 08/16/1990
• Issued: 05/26/1992
• Est. Priority Date: 08/16/1990
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Feintuch, Paul L.
• Primary Examiner(s): Pihulic, Daniel T.
• Application Number:
  US07/568,289
• Time in Patent Office: 649 Days
• Field of Search: 367/901, 367/137, 367/1, 367/135, 381/71, 381/94, 364/574, 364/724.19, 181/206
• US Class Current: 367/135
• CPC Class Codes: G10K 11/17817 between the output signals and the error signals, i.e. secondary path
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17881 the reference signal being an acoustic signal, e.g. recorded with a microphone
• CPC Class Codes: G10K 2210/30232 Transfer functions, e.g. impulse response
• CPC Class Codes: G10K 2210/3045 Multiple acoustic inputs, single acoustic output
• CPC Class Codes: G10K 2210/3053 Speeding up computation or convergence, or decreasing the computational load
• CPC Class Codes: G10K 2210/503 Diagnostics; Stability; Alarms; Failsafe
• CPC Class Codes: Y10S 367/901 Noise or unwanted signal reduction in nonseismic receiving system

Abstract

An active adaptive noise canceller that inserts delays in the weight update logic of an adaptive filter employed by the canceller to make the filter stable. It has been found that there is a great deal of flexibility regarding the selection of the delay values. This insensitivity permits designing the delays in advance, and not having to adjust them to different situations as they change, thus no longer requiring a training mode. The canceller dramatically reduces the amount of hardward needed to perform active adaptive noise cancelling, and eliminates the need for the training mode, which in some applications, including automobiles, for example, can be as objectionable as the noise sources that are to be suppressed.

Claims

1. An active adaptive canceller for use in suppressing noise signals derived from a noise source, said active adaptive canceller comprising:

a noise sensor;

an acoustic sensor;

an acoustic output device;

delay means coupled to the noise sensor for delaying the noise signals generated thereby by a preselected time delay; and

adaptive filter means having a plurality of inputs coupled to the noise sensor, the acoustic sensor, and the delay means, and an output coupled to the acoustic output device;

wherein the delay means causes the active adaptive canceller to be stable and to not require a training mode.

2. The active adaptive canceller of claim 1 wherein the adaptive filter means comprises a plurality of adjustable filter weight inputs, and weight update logic circuitry coupled to the plurality of adjustable filter weight inputs and to the delay means for receiving output signals from the acoustic sensor and delayed output signals from the delay means and for adjusting the filter weights applied to the adjustable filter weight inputs.

3. The active adaptive canceller of claim 1 wherein the adaptive filter means and delay means comprises:

first adaptive filter means having an input and an output;

second adaptive filter means having an input and an output;

adder means coupled to the outputs of the first and second adaptive filter means for combining the output signals provided thereby to provide filtered output signals and for applying the filtered output signals to the output device;

first delay means coupled to the first adaptive filter means for delaying the filtered output signals coupled thereto by a first predetermined time delay; and

second delay means coupled to the second adaptive filter means for delaying the noise signals coupled thereto by a second predetermined time delay.

4. The active adaptive canceller of claim 3 wherein the first and second predetermined time delays are substantially the same.

5. The active adaptive canceller of claim 1 wherein the adaptive filter means and delay means comprises:

first adaptive filter means having an input and an output and including a plurality of adjustable filter weight inputs;

second adaptive filter means having an input and an output and including a plurality of adjustable filter weight inputs;

adder means coupled to the outputs of the first and second adaptive filter means for combining the output signals provided thereby to provide filtered output signals and for applying the filtered output signals to the output device;

first weight update logic circuitry coupled to the first adaptive filter means for receiving input signals comprising the filtered output signals and output signals from the acoustic sensor and for adjusting the filter weights applied to the adjustable filter weight inputs of the first adaptive filter means;

second weight update logic circuitry coupled to the second adaptive filter means for receiving input signals comprising the background noise signals and output signals from the acoustic sensor and for adjusting the filter weights applied to the adjustable filter weight inputs of the second adaptive filter means;

first delay means coupled to the first weight update logic circuitry for delaying the filtered output signals coupled to the first weight update logic circuitry by a predetermined time delay; and

second delay means coupled to the second weight update logic circuitry for delaying the background noise signals coupled to the second weight update logic circuitry by a predetermined time delay.

6. An active adaptive canceller for use in suppressing noise signals derived from a noise source, said active adaptive canceller comprising:

a noise sensor adapted to sense the noise signals;

an acoustic sensor;

an acoustic output device;

an adaptive filter coupled between the noise sensor and the acoustic output device;

delay means coupled to the noise sensor for delaying the noise signals generated thereby by a preselected time delay; and

weight update logic circuitry coupled between the the adaptive filter means and the delay means for receiving output signals from the acoustic sensor and delayed output signals from the delay means and for adjusting the filter weights applied to the adjustable filter weight inputs of the adaptive filter;

wherein the delay means causes the active adaptive canceller to be stable and to not require a training mode.

7. An adaptive canceller for use in eliminating noise from a system comprising a noise sensor, a speaker and an microphone that function in the presence of background noise signals, said adaptive canceller comprising:

a first adaptive filter having an input and an output and including a plurality of adjustable filter weight inputs;

a second adaptive filter having an input and an output and including a plurality of adjustable filter weight inputs;

means for combining the output signals provided by the first and second adaptive filters to provide filtered output signals and for applying the filtered output signals to the speaker;

first weight update logic circuitry coupled to the first adaptive filter for receiving input signals comprising the filtered output signals and output signals from the microphone and for adjusting the filter weights applied to the adjustable filter weight inputs of the first adaptive filter;

second weight update logic circuitry coupled to the second adaptive filter for receiving input signals comprising the background noise signals and output signals from the microphone and for adjusting the filter weights applied to the adjustable filter weight inputs of the second adaptive filter;

a first delay circuit coupled to the first weight update logic circuitry for delaying the filtered output signals coupled to the first weight update logic circuitry by a predetermined time delay; and

a second delay circuit coupled to the second weight update logic circuitry for delaying the background noise signals coupled to the second weight update logic circuitry by a predetermined time delay.

8. An adaptive canceller for use in eliminating noise from a system comprising a noise sensor, a speaker and a microphone that function in the presence of background noise signals, said adaptive canceller comprising:

first adaptive filter means having an input and an output and including a plurality of adjustable filter weight inputs;

second adaptive filter means having an input and an output and including a plurality of adjustable filter weight inputs;

adder means coupled to the outputs of the first and second adaptive filter means for combining the output signals provided thereby to provide filtered output signals and for applying the filtered output signals to the speaker;

first weight update logic circuitry coupled to the first adaptive filter means for receiving input signals comprising the filtered output signals and output signals from the microphone and for adjusting the filter weights applied to the adjustable filter weight inputs of the first adaptive filter means;

second weight update logic circuitry coupled to the second adaptive filter means for receiving input signals comprising the background noise signals and output signals from the microphone and for adjusting the filter weights applied to the adjustable filter weight inputs of the second adaptive filter means;

first delay means coupled to the first weight update logic circuitry for temporally delaying the filtered output signals coupled to the first weight update logic circuitry by a predetermined fixed time delay; and

second delay means coupled to the second weight update logic circuitry for temporally delaying the background noise signals coupled to the second weight update logic circuitry by a predetermined fixed time delay.

9. An active adaptive canceller for use in suppressing acoustic noise signals generated by an acoustic noise source, said active adaptive canceller comprising:

a first sensor for receiving said noise signals and providing a signal representative of said noise signals;

an output device for generating acoustic cancelling signals for cancelling said acoustic noise signals;

a second sensor for receiving the acoustic noise signals and said acoustic cancelling signals to provide combined acoustic signals;

a delay means for delaying the signals representative of said noise signals by a preselected time delay to provide delayed signals representative of said noise signals, said time related to the combined delay attributed to the transfer function of the output device and the second sensor; and

an adaptive filter having its signal input coupled to receive said signals representative of said noise signals, said adaptive filter having its weight update logic coupled to receive the delayed signals representative of said noise signals and the output of said second sensor, the output of said adaptive filter coupled to said output device.

10. An active adaptive canceller as recited in claim 9 further including a second delay means for delaying signals at its input by a preselected time delay to provide delayed signals at its output, said time of the delay related to the combined delay of the transfer function of the output device and the second sensor;

and wherein said adaptive filter comprises;

a first adaptive filter;

a second adaptive filter; and

an adder having at least two inputs and an output;

the second adaptive filter having its signal input coupled to receive said signals representative of said noise signals, said adaptive filter having its weight update logic coupled to receive the delayed signals representative of said noise signals and the output of said second sensor to receive, the output of said second adaptive filter coupled to one input of said adder;

the output of said adder coupled to said output device and to the input of said second delay means;

the first adaptive filter having its signal input coupled to receive the output of said adder, said first adaptive filter having its weight update logic coupled to receive the output of said second delay means and the output of said second sensor.