Active noise control using variable step-size adaptation

• US 10,163,432 B2
• Filed: 02/23/2017
• Issued: 12/25/2018
• Est. Priority Date: 02/23/2017
• Status: Active Grant

• Current Assignee: Blackberry Limited
• Original Assignee: 2236008 Ontario Inc. (Blackberry Limited)
• Inventors: Every, Mark Robert
• Primary Examiner(s): Patel, Yogeshkumar
• Application Number:
  US15/440,977
• Publication Number:
  US 20180240452A1
• Time in Patent Office: 670 Days
• Field of Search: 381 7111, 381 711, 381 941, 381 86, 381 93, 704E21014, 375232, 37940608, 37940609
• CPC Class Codes: G10K 11/178 by electro-acoustically regenerating the original acoustic waves in anti-phase
• CPC Class Codes: G10K 2210/1282 Automobiles
• CPC Class Codes: G10K 2210/12821 Rolling noise; Wind and body noise
• CPC Class Codes: G10K 2210/3028 Filtering, e.g. Kalman filters or special analogue or digital filters
• CPC Class Codes: G10K 2210/3046 Multiple acoustic inputs, multiple acoustic outputs
• CPC Class Codes: G10K 2210/3054 Stepsize variation
• CPC Class Codes: G10K 2210/3055 Transfer function of the acoustic system

Abstract

A system and method (referred to as the system) that actively reduces noise in a vehicle. The system generates one or more control output signals to drive multiple loudspeakers; and adapts multiple control coefficients of a control filter based on multiple secondary path transfer functions. The secondary path transfer functions model the acoustic paths between each loudspeaker and multiple microphones. The multiple control coefficients are time varying and frequency dependent and the rate the plurality control coefficients adapt is based on an adaptive step size based on one or more step size criteria.

Claims

1. A method that actively cancels noise in a vehicle using a plurality of microphones and a plurality of loudspeakers comprising:

generating one or more control output signals to drive the plurality of loudspeakers; and

adapting a plurality of control coefficients of a control filter based on a plurality of secondary path transfer functions that model the acoustic paths between each loudspeaker and each microphone of the plurality of microphones;

where the rate the plurality of control coefficients of the control filter adapt is time-varying and frequency dependent; and

where the rate the plurality of control coefficients of the control filter adapt is based on an adaptive step size based on a predetermined secondary acoustic path.

2. The method of claim 1 where the plurality of secondary path transfer functions are measured by transmitting a signal through each of the plurality of loudspeakers and measuring the audio response at each of the plurality of microphones.

3. The method of claim 1 further comprising estimating a frequency-dependent group delay from the plurality of secondary path transfer functions.

4. The method of claim 3 where the adaptive step size is inversely related to the frequency-dependent group delay.

5. The method of claim 1 further comprising estimating a frequency-dependent phase delay from the plurality of secondary path transfer functions.

6. The method of claim 1 where the adaptive step size is inversely related to the frequency-dependent phase delay.

7. The method of claim 1 further comprising estimating an overall delay from the plurality of secondary path transfer functions.

8. The method of claim 7 where the adaptive step size is inversely related to the estimated overall delay.

9. The method of claim 1 where the adaptive step size is based on the predetermined secondary acoustic path and step size criterion.

10. A non-transitory machine-readable medium encoded with machine-executable instructions, where execution of the machine-executable instructions:

generates one or more control output signals to drive a plurality of loudspeakers; and

adapts a plurality of control coefficients of a control filter based on a plurality of secondary path transfer functions that model the acoustic paths between each loudspeaker and a plurality of microphones;

where the rate the plurality of control coefficients of the control filter adapt is time-varying and frequency dependent; and

where the rate the plurality of control coefficients of the control filter adapt is based on an adaptive step size based on a step size criterion.

11. The non-transitory machine-readable medium of claim 10 where the step size criterion comprises one or more energy thresholds that are compared to the energies of the control output signals generated by the control filter.

12. The non-transitory machine-readable medium of claim 10 where the step size criterion comprises separate energy thresholds that are compared to different components of the control output signals generated by the control filter that are associated with individual engine orders.

13. The non-transitory machine-readable medium of claim 10 further comprising ceasing the adaption of the plurality of control coefficients of the control filter when the energy level of a control output signal generated by the control filter exceeds an energy threshold.

14. The non-transitory machine-readable medium of claim 10 where the step size criterion comprises set energy thresholds dependent on a vehicle'"'"'s operating state.

15. The non-transitory machine-readable medium of claim 14 where the vehicle'"'"'s operating state is measured by the revolutions per minute of the vehicle'"'"'s engine.

16. The non-transitory machine-readable medium of claim 10 where the step size criterion comprises microphone self-noise.

17. The non-transitory machine-readable medium of claim 10 where the step size criterion is based on an electric current draw of each loudspeaker or an impedance of each loudspeaker.

18. The non-transitory machine-readable medium of claim 10 where the step size criterion comprises a measure of correlation over time between control output signals generated by the control filter and each of a plurality of microphone input signals.

19. The non-transitory machine-readable medium of claim 10 where the step size criterion comprises a predetermined measure of statistical variance of the plurality of control coefficients of the control filter.

20. The non-transitory machine-readable medium of claim 10 where the step size criterion comprises two or more step size criteria based on:

a group delay or a phase delay of the acoustic paths between each loudspeaker and each microphone;

a measure of correlation over time between control output signals generated by the control filter and each of a plurality of microphone input signals;

a comparison of control output signal energies to predetermined thresholds;

or

a predetermined measure of statistical variance of the plurality of control coefficients of the control filter.

21. An active noise control system comprising:

control filter means that generates one or more control output signals to drive a plurality of loudspeakers in response to an external audio source; and

control filter update means that adapts a plurality of control coefficients of the control filter means based on a plurality of secondary path transfer functions that model the acoustic paths between a plurality of loudspeakers and a plurality of microphones; and

divergence detection means that controls the adaption rate of the plurality of control coefficients in response to a step size criteria;

where the plurality of plurality control coefficients are time varying and frequency dependent.