Field check for hearing protection devices

1 . A method to check a relative sensitivity of two or more microphones of a hearing protection device, the method comprising:

sensing ambient sound using the two or more microphones of the hearing protection device;

sampling the ambient sound to produce a plurality of audio samples of the ambient sound;

determining whether the ambient sound is adequate for determining microphone sensitivity by determining a coherence of the two or more microphones based on the plurality of audio samples of the ambient sound;

determining whether a relative sensitivity of the two or more microphones is within a threshold range based on the plurality of audio samples of the ambient sound; and

providing a pass or fail indication to a user based on the determining of whether the threshold relative sensitivity is reached.

2 . The method of claim 1 , wherein determining whether the ambient sound is adequate for determining microphone sensitivity comprises determining an overall energy of each of the two or more microphones based on the plurality of audio samples of the ambient sound.

3 . The method of claim 1 , wherein determining the coherence of the two or more microphones comprises comparing spectrums of the two or more microphones at one or more frequencies based on the plurality of audio samples of the ambient sound.

4 . The method of claim 3 , wherein the one or more frequencies comprise 250 Hertz and 1 Kilohertz.

5 . The method of claim 1 , determining whether a threshold relative sensitivity of the two or more microphones is reached comprises:

determining a sound pressure level for each of the two or more microphones based on the plurality of audio samples of the ambient sound;

determining a difference between the sound pressure level of each of the two or more microphones; and

determining whether the difference between the sound pressure level of each of the two or more microphones is within a threshold range.

6 . The method of claim 1 , wherein determining whether the relative sensitivity of the two or more microphones is reached comprises comparing the plurality of audio samples of ambient sound to a predetermined reference.

7 . The method of claim 1 , further comprising determining a presence of one or more test invalidation conditions based on the plurality of audio samples of the ambient sound.

8 . The method of claim 1 , wherein determining whether the ambient sound is adequate for determining microphone sensitivity comprises comparing the coherence to a threshold coherence.

9 . The method of claim 8 , wherein the threshold coherence is at least 0.7.

10 . The method of claim 1 , wherein determining a coherence of the two or more microphones is performed overall and in one or more frequency bands based on the plurality of audio samples of the ambient sound.

11 . A hearing protection device comprising:

two or more microphones to sense sound of an environment; and

a controller comprising one or more processors and operatively coupled to the two or microphones to check a relative sensitivity of two or more microphones, the controller configured to:

sample ambient sound sensed by the two or more microphones to produce a plurality of audio samples of the ambient sound;

determine whether the ambient sound is adequate for determining microphone sensitivity based on the plurality of audio samples of the ambient sound;

determine whether a relative sensitivity of the two or more microphones is within a threshold range based on the plurality of audio samples of the ambient sound; and

provide a pass indication to a user based on the determining of whether the threshold relative sensitivity is reached.

12 . The device of claim 11 , wherein to determine whether the ambient sound is adequate for determining microphone sensitivity, the controller is configured to determine a coherence of the two or more microphones based on the plurality of audio samples of the ambient sound.

13 . The device of claim 12 , wherein to determine the coherence of the two or more microphones, the controller is configured to compare waveforms of the two or more microphones at one or more frequencies based on the plurality of audio samples of the ambient sound.

14 . The device of claim 13 , wherein the one or more frequencies comprise 250 Hertz and 1 Kilohertz.

15 . The device of claim 11 , wherein the controller is further configured to adapt one or more filters based on the plurality of audio samples of the ambient sound.

16 . The device of claim 11 , wherein to determine whether the ambient sound is adequate for determining microphone sensitivity, the controller is further configured to determine a band-wise energy of each of the two or more microphones based on the plurality of audio samples of the ambient sound.

17 . The device of claim 11 , wherein to determine whether a threshold relative sensitivity of the two or more microphones is reached, the controller is further configured to:

determine a sound pressure level for each of the two or more microphones based on the plurality of audio samples of the ambient sound;

determine a difference between the sound pressure level of each of the two or more microphones; and

determine whether the difference between the sound pressure level of each of the two or more microphones is within a threshold range.

18 . The device of claim 11 , wherein to determine whether the relative sensitivity of the two or more microphones is reached, the controller is configured to compare the plurality of audio samples of ambient sound to a predetermined reference.

19 . The device of claim 11 , wherein the controller is further configured to determine a presence of one or more test invalidation conditions based on the plurality of audio samples of the ambient sound.

20 . A hearing protection device comprising:

two or more microphones to sense sound of an environment; and

a controller comprising one or more processors and operatively coupled to the two or microphones to check a relative sensitivity of two or more microphones, the controller configured to:

sample ambient sound sensed by the two or more microphones to produce a plurality of audio samples of the ambient sound;

determine whether the ambient sound is adequate for determining microphone sensitivity based on the plurality of audio samples of the ambient sound by: (i) determining, from the audio samples, band-wise energy for each microphone and requiring at least one frequency band to exceed 70 dB Sound Pressure Level, and (ii) determining inter-microphone coherence and requiring the coherence at 250 Hz and at 1 kHz to be at least 0.7;

determine whether a relative sensitivity of the two or more microphones is within a threshold range based on the plurality of audio samples of the ambient sound; and

provide a pass or fail indication to a user based on the determining of whether the threshold relative sensitivity is reached.