Methods and apparatus for recording impulsive sounds

Patent metadata

Field	Value
Publication number	US-9478229-B2
Application number	US-201314101802-A
Country	US
Kind code	B2
Filing date	Dec 10, 2013
Priority date	Dec 10, 2013
Publication date	Oct 25, 2016
Grant date	Oct 25, 2016

Abstract

Loud sounds with fast rise times, like gunfire and explosions, can cause noise-induced hearing loss (NIHL). Unfortunately, current models do not adequately explain how impulsive sounds cause NIHL, which makes it difficult to predict and prevent NIHL on battlefields and other hostile or rugged environments. Fortunately, the impulsive sounds experienced by soldiers and others working in rugged environments can be recorded using a compact, portable system that acquires, digitizes, and stores high-bandwidth audio data. An example of this system can be mounted on a helmet or other article and used to record hours of audio data at a bandwidth of 20 kHz or higher, which is broad enough to capture sounds with rise times less than 50 ms. An analog-to-digital converter (ADC) digitizes these broadband audio signals at rate of 40 kHz or higher to preserve the impulse information. A processor transfers the digitized samples from a buffer to a memory card for later retrieval using an interrupt-driven processing technique.

First claim

The invention claimed is:

1. A portable system for continuously recording sound pressure due to both continuous noise and impulse noise in an environment, the portable system comprising:
a first microphone to produce a first analog signal representative of impulse noise sound pressure in a first amplitude range from about 100 dB to about 180 dB;
a second microphone to produce a second analog signal representative of continuous noise sound pressure in a second amplitude range from about 20 dB to about 140 dB, the second amplitude range being different from the first amplitude range;
at least one analog-to-digital converter (ADC), operably coupled to the first microphone and the second microphone, to sample:
the first analog signal at a first sampling rate equal to or greater than twice the reciprocal of a minimum impulse noise rise time in the first analog signal, thereby generating a first digital signal; and
the second analog signal at a second sampling rate equal to or greater than twice the reciprocal of a minimum impulse noise rise time in the second analog signal, thereby generating a second digital signal;

a combining node, operably coupled to the at least one ADC, to combine the first digital signal and the second digital signal into a combined digital signal having a combined amplitude range, the combined amplitude range being larger than the first amplitude range, larger than the second amplitude range, and less than or about equal to the sum of the first amplitude range and the second amplitude range, the combined digital signal representing both the continuous noise and the impulse noise in the environment; and
a processor, operably coupled to the combining node, to store a representation of the combined digital signal in a nonvolatile memory.

2. The portable system of claim 1 , wherein:
the first amplitude range is from about 115 dB to about 180 dB;
the second amplitude range is from about 75 dB to about 140 dB; and
the combined amplitude range is less than about 105 dB.

3. The portable system of claim 1 , further comprising:
an attenuator, operably coupled to an output of the first microphone and a first input of the at least one ADC, to attenuate the first analog signal; and
an amplifier, operably coupled to an output of the second microphone and a second input of the at least one ADC, to amplify the second analog signal.

4. The portable system of claim 1 , wherein the sampling rate is about 20 kHz to about 200 kHz.

5. The portable system of claim 1 , wherein the processor is configured to identify at least one output representing at least one type of noise from the combined digital signal.

6. The portable system of claim 1 , wherein the processor is configured to:
(i) divide the combined digital signal into a plurality of time-frequency bins;
(ii) estimate an amount of energy in each time-frequency bin in the plurality of time-frequency bins to produce a plurality of energy estimates; and
(iii) store the plurality of energy estimates in the nonvolatile memory as a first output representing at least continuous background noise from the combined digital signal.

7. The portable system of claim 6 , wherein the plurality of time-frequency bins are selected using a frequency spacing, the frequency spacing being at least one of logarithmic, linear, octave, and fractional octave.

8. The portable system of claim 6 , wherein the plurality of time-frequency bins are selected using a time interval of about 200 ms.

9. The portable system of claim 1 , wherein the processor is configured to:
(i) remove from the combined digital signal any samples having an amplitude less than a particular amplitude threshold and any samples having a duration exceeding a particular duration threshold; and
(ii) store the remaining samples from the combined digital signal in the nonvolatile memory as a second output representing at least impulse noise from the combined digital signal.

10. The portable system of claim 9 , wherein the particular amplitude threshold is about 125 dB.

11. The portable system of claim 9 , wherein the particular duration threshold is about 40 ms to about 70 ms.

12. The portable system of claim 9 , wherein the second output excludes recoverable speech content.

13. The portable system of claim 1 , further comprising:
a communications interface, operably coupled to the processor, to transmit the representation of the combined digital signal over a network to an electronic device.

14. A method of continuously recording sound pressure due to both continuous noise and impulse noise in an environment, the method comprising:
(A) producing, with a first microphone, a first analog signal representative of impulse noise sound pressure in a first amplitude range from about 100 dB to about 180 dB;
(B) producing, with a second microphone, a second analog signal representative of continuous noise sound pressure in a second amplitude range from about 20 dB to about 140 dB, the second amplitude range being different from first amplitude range;
(C) sampling, with at least one analog-to-digital converter (ADC):
(i) the first analog signal at a first sampling rate equal to or greater than twice the reciprocal of a minimum impulse noise rise time in the first analog signal, thereby generating a first digital signal; and
(ii) the second analog signal at a second sampling rate equal to or greater than twice the reciprocal of a minimum impulse noise rise time in the second analog signal, thereby generating a second digital signal;

(D) combining the first digital signal and the second digital signal into a combined digital signal having a combined amplitude range, the combined amplitude range being larger than the first amplitude range, larger than the second amplitude range, and less than or about equal to the sum of the first amplitude range and the second amplitude range, the combined digital signal representing both the continuous noise and the impulse noise in the environment; and
(E) storing a representation of the combined digital signal in a nonvolatile memory.

15. The method of claim 14 , wherein (A) comprises at least one of:
wearing at least one of the first microphone and the second microphone on at least one of an article of clothing, a headgear, a web gear, and a bag in the environment; and
mounting at least one of the first microphone and the second microphone to at least one of a portable device, a vehicle, and a fixture in the environment.

16. The method of claim 14 , wherein:
the first amplitude range is from about 115 dB to about 180 dB;
the second amplitude range is from about 75 dB to about 140 dB; and
the combined amplitude range is less than about 105 dB.

17. The method of claim 14 , wherein (C) further comprises:
attenuating the first analog signal to produce an attenuated analog signal for sampling with the at least one ADC to generate the first digital signal; and
amplifying the second analog signal to produce an amplified analog signal for sampling with the at least one ADC to generate the second digital signal.

18. The method of claim 14 , wherein the sampling rate is about 20 kHz to about 200 kHz.

19. The method of claim 14 , further comprising:
removing from the combined digital signal any samples having an amplitude less than a particular amplitude threshold and any samples having a duration exceeding a particular duration threshold; and
storing the remaining samples of the combined digital signal in the nonvolatile memory as a first output representing at least impulse nois

Assignees

• Lacirignola Joseph J
• Vian Trina Rae
• Aubin Jr David F
• Quatieri Thomas F
• Fischl Kate D
• Collins Paula P
• Smalt Christopher J
• Gatewood Paul D
• Malyska Nicolas
• Maurer David C
• Massachusetts Inst Technology

Inventors

• Lacirignola Joseph J
• Vian Trina Rae
• Aubin Jr David F
• Quatieri Thomas F
• Fischl Kate D
• Collins Paula P
• Smalt Christopher J
• Gatewood Paul D
• Malyska Nicolas
• Maurer David C

Classifications

• G11B20/24

  for reducing noise {(control of amplification in general, e.g. dependent upon noise level H03G)} · CPC title

• G10L21/0208 Primary

  Noise filtering · CPC title

• H04R3/005

  for combining the signals of two or more microphones (specially adapted for hearing aids H04R25/407) · CPC title

• H04R25/75 Primary

  Electric tinnitus maskers providing an auditory perception · CPC title

• H04R2460/07

  Use of position data from wide-area or local-area positioning systems in hearing devices, e.g. program or information selection · CPC title