Breathing Apparatus Speech Enhancement

• US 20090192799A1
• Filed: 01/29/2008
• Published: 07/30/2009
• Est. Priority Date: 01/29/2008
• Status: Active Grant

• Current Assignee: Digital Voice Systems, Inc.
• Original Assignee: Digital Voice Systems, Inc.
• Inventors: Griffin, Daniel W., Hardwick, John C.
• Granted Patent: US 8,265,937 B2
• Time in Patent Office: Days
• US Class Current: 704/270
• CPC Class Codes: A62B 18/08 Component parts for gas-masks or gas-helmets, e.g. windows, straps, speech transmitters, signal-devices eye-pieces for protective goggles A61F9/02; composition of materials for the windows or other transparent parts A62D7/00
• CPC Class Codes: G10L 2021/02165 Two microphones, one receiving mainly the noise signal and the other one mainly the speech signal
• CPC Class Codes: G10L 2021/03643 Diver speech
• CPC Class Codes: G10L 21/0208 Noise filtering
• CPC Class Codes: G10L 21/0364 for improving intelligibility
• CPC Class Codes: H04R 1/1083 Reduction of ambient noise active noise reduction per se G10K11/175; protective devices for the ear, e.g. providing acoustic protection A61F11/06
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

Speech enhancement in a breathing apparatus is provided using a primary sensor mounted near a breathing mask user'"'"'s mouth, at least one reference sensor mounted near a noise source, and a processor that combines the signals from these sensors to produce an output signal with an enhanced speech component. The reference sensor signal may be filtered and the result may be subtracted from the primary sensor signal to produce the output signal with an enhanced speech component. A method for detecting the exclusive presence of a low air alarm noise may be used to determine when to update the filter. A triple filter adaptive noise cancellation method may provide improved performance through reduction of filter maladaptation. The speech enhancement techniques may be employed as part of a communication system or a speech recognition system.

Claims

1. A breathing apparatus speech enhancement system comprising:

a breathing mask;

a primary sensor on the breathing mask and configured to produce a primary signal;

at least one reference sensor on the breathing mask and configured to produce a reference signal; and

,

a processor which combines at least the primary signal and the reference signal to produce an output signal with an enhanced speech component.

2. The system of claim 1 wherein the primary sensor is a microphone.

3. The system of claim 2 wherein the primary sensor is a microphone of the noise cancelling or gradient type.

4. The system of claim 1 wherein at least one reference sensor is a microphone.

5. The system of claim 4 wherein at least one reference sensor is a microphone of the noise cancelling or gradient type.

6. The system of claim 1 wherein the primary sensor is mounted on the breathing mask so as to be near the mouth of a user wearing the breathing mask.

7. The system of claim 1 wherein the breathing mask includes a voice port and the primary sensor is mounted externally to the mask near the voice port.

8. The system of claim 1 wherein at least one reference sensor is mounted near a noise source.

9. The system of claim 1 wherein the breathing mask includes a breath screen to shield at least one reference sensor to reduce the impact of air flow from the user'"'"'s mouth.

10. The system of claim 1 further comprising a wireless transmitter connected to transmit the primary signal wirelessly.

11. The system of claim 1 further comprising a wireless transmitter connected to transmit at least one reference signal wirelessly.

12. A communication system including the system of claim 1.

13. The system of claim 1 further comprising a speech recognition system configured to process the output signal with the enhanced speech component.

14. The system of claim 1 wherein the processor is configured to use a filter to filter the reference signal and subtract the filtered reference signal from the primary signal to produce the output signal.

15. The system of claim 14 wherein the processor is configured to update the filter based on a the output signal and the reference signal.

16. The system of claim 15 wherein the processor is configured to only update the filter when the processor detects the exclusive presence of an alarm signal by:

receiving the primary signal;

determining the energy of the primary signal;

determining a peak count of the number of consecutive energy samples below a first threshold;

determining a valley count of the number of consecutive energy samples above a second threshold;

determining an alarm count of the number of consecutive samples for which the peak count and valley count are below a third threshold; and

declaring the exclusive presence of the alarm signal when the alarm count exceeds a fourth threshold.

17. The system of claim 14 wherein the processor is configured to update the filter in a transform domain to improve a convergence rate of the filter.

18. The system of claim 1 wherein the processor is configured to:

receive the primary signal;

receive the reference signal;

filter the reference signal with an output filter to produce an output filtered reference signal;

subtract the output filtered reference signal from the primary signal to produce an output signal;

filter the reference signal with an evaluation filter to produce an evaluation filtered reference signal;

subtract the evaluation filtered reference signal from the primary signal to produce an evaluation signal;

filter the reference signal with an update filter to produce an update filtered reference signal;

subtract the update filtered reference signal from the primary signal to produce an update signal;

modify the update filter based on the reference signal and the update signal;

modify the evaluation filter based on the update filter; and

modify the output filter based on the output signal and the evaluation signal.

19. The system of claim 18 wherein the processor is configured to only modify the filters when the processor detects the exclusive presence of an alarm signal by:

receiving the primary signal;

determining the energy of the primary signal;

is determining a peak count of the number of consecutive energy samples below a first threshold;

determining a valley count of the number of consecutive energy samples above a second threshold;

determining an alarm count of the number of consecutive samples for which the peak count and valley count are below a third threshold; and

declaring the exclusive presence of the alarm signal when the alarm count exceeds a fourth threshold.

20. A method of analyzing a digitized audio signal to detect the exclusive presence of an alarm signal, the method comprising:

receiving a digitized audio signal;

determining the energy of the digitized audio signal;

determining a peak count of the number of consecutive energy samples below a first threshold;

determining a valley count of the number of consecutive energy samples above a second threshold;

determining an alarm count of the number of consecutive samples for which the peak count and valley count are below a third threshold; and

declaring the exclusive presence of the alarm signal when the alarm count exceeds a fourth threshold.

21. A system for analyzing a digitized audio signal to detect the exclusive presence of an alarm signal, the system comprising a processor configured to:

receive a digitized audio signal;

determine the energy of the digitized audio signal;

determine a peak count of the number of consecutive energy samples below a first threshold;

determine a valley count of the number of consecutive energy samples above a second threshold;

determine an alarm count of the number of consecutive samples for which the peak count and valley count are below a third threshold; and

declare the exclusive presence of the alarm signal when the alarm count exceeds a fourth threshold.

22. A method of processing a digitized primary audio signal to reduce a noise component of the primary audio signal, the method comprising:

receiving a digitized primary audio signal;

receiving at least one digitized reference audio signal;

filtering the at least one reference signal with an output filter to produce an output filtered reference signal;

subtracting the output filtered reference signal from the primary signal to produce an output signal;

filtering the at least one reference signal with an evaluation filter to produce an evaluation filtered reference signal;

subtracting the evaluation filtered reference signal from the primary signal to produce an evaluation signal;

filtering the at least one reference signal with an update filter to produce an update filtered reference signal;

subtracting the update filtered reference signal from the primary signal to produce an update signal;

modifying the update filter based on the reference signal and the update signal;

modifying the evaluation filter based on the update filter; and

modifying the output filter based on the output signal and the evaluation signal.

23. The method of claim 22 wherein the update filter is modified only when the exclusive presence of a noise signal is declared.

24. The method of claim 23 further comprising:

receiving a digitized audio signal;

determining the energy of the digitized audio signal;

determining a peak count of the number of consecutive energy samples below a first threshold;

determining a valley count of the number of consecutive energy samples above a second threshold;

determining an alarm count of the number of consecutive samples for which the peak count and valley count are below a third threshold; and

declaring the exclusive presence of a noise signal when the alarm count exceeds a fourth threshold.