Beamforming in varying sound pressure level

Patent metadata

Field	Value
Publication number	US-9326060-B2
Application number	US-201414451039-A
Country	US
Kind code	B2
Filing date	Aug 4, 2014
Priority date	Aug 4, 2014
Publication date	Apr 26, 2016
Grant date	Apr 26, 2016

Abstract

A method that uses a microphone array for spatially selective sound pickup during an audio-video recording session is described. An audio signal for the audio-video recording session is generated using a beamforming process from the microphone array in accordance with a sound pickup directivity pattern. Ambient sound pressure level of the audio-video recording session is monitored while generating the audio signal. The sound pickup directivity pattern of the beamforming process is automatically adjusted during the audio-video recording session as a function of the monitored ambient sound pressure level. Other embodiments are also described and claimed.

First claim

What is claimed is:

1. A method of using a microphone array for spatially selective sound pickup during an audio-video recording session, the method comprising:
generating, using a beamforming process, an audio signal for the audio-video recording session from the microphone array in accordance with a sound pickup directivity pattern;
monitoring ambient sound pressure level of the audio-video recording session while generating the audio signal; and
automatically adjusting the sound pickup directivity pattern of the beamforming process during the audio-video recording session as a function of the monitored ambient sound pressure level.

2. The method of claim 1 , wherein a low directivity pattern is used for the beamforming process when the monitored ambient sound pressure level is below a first sound level threshold and a high directivity pattern is used for the beamforming process when the monitored ambient sound pressure level is above a second sound level threshold.

3. The method of claim 2 , wherein the first sound level threshold is the same as the second sound level threshold.

4. The method of claim 2 , wherein the first sound level threshold is lower than the second sound level threshold.

5. The method of claim 2 , wherein the low directivity pattern has a directivity index that is less than 4.8 dB.

6. The method of claim 5 , wherein the high directivity pattern has a directivity index that is equal to or greater than 4.8 dB.

7. The method of claim 2 , wherein the low directivity pattern is omnidirectional or sub-cardioid, and the high directivity pattern is a cardioid, super-cardioid, or hyper-cardioid.

8. The method of claim 1 further comprising automatically adjusting white noise gain (WNG) of the beamforming process during the audio-video recording session as a function of the monitored ambient sound pressure level.

9. The method of claim 8 , wherein a strict WNG constraint is used when the monitored ambient sound pressure level is below a third sound level threshold and a loose WNG constraint is used when the monitored ambient sound pressure level is above a fourth sound level threshold.

10. The method of claim 9 , wherein the third sound level threshold is lower than the fourth sound level threshold.

11. The method of claim 1 , wherein the function maps higher ambient sound pressure levels to higher directivity indexes for the sound pickup directivity pattern of the beamforming process.

12. A handheld device comprising:
a camera that is to record video;
a microphone array that is to capture audio;
a sound level monitor that is to monitor ambient sound pressure level; and
an audio processor that is to generate, using a beamforming process, an audio signal from the microphone array in accordance with a sound pickup directivity pattern, and to automatically adjust the sound pickup directivity pattern of the beamforming process as a function of the monitored ambient sound pressure level.

13. The handheld device of claim 12 , wherein the audio processor adjusts the sound pickup directivity pattern of the beamforming process by adjusting a directivity index of the sound pickup directivity pattern based on the monitored ambient sound pressure level.

14. The handheld device of claim 12 , wherein a low directivity pattern is used for the beamforming process when the monitored ambient sound pressure level is below a first sound level threshold and a high directivity pattern is used for the beamforming process when the monitored ambient sound pressure level is above a second sound level threshold.

15. The handheld device of claim 14 , wherein the audio processor further is to automatically adjust white noise gain (WNG) of the beamforming process as a function of the monitored ambient sound pressure level.

16. The handheld device of claim 15 , wherein a strict WNG constraint is used when the monitored ambient sound pressure level is below a third sound level threshold and a loose WNG constraint is used when the monitored ambient sound pressure level is above a fourth sound level threshold.

17. A method of using a microphone array for spatially selective sound pickup during an audio-video recording session, the method comprising:
generating, using a beamforming process, an audio signal for the audio-video recording session from the microphone array in accordance with a sound pickup directivity pattern;
monitoring ambient sound pressure level of the audio-video recording session while generating the audio signal; and
automatically adjusting white noise gain (WNG) of the beamforming process as a function of the monitored ambient sound pressure level.

18. The method of claim 17 , wherein a strict WNG constraint is used when the monitored ambient sound pressure level is below a first sound level threshold and a loose WNG constraint is used when the monitored ambient sound pressure level is above a second sound level threshold.

19. The method of claim 18 , wherein the first sound level threshold is the same as the second sound level threshold.

20. The method of claim 18 , wherein the first sound level threshold is lower than the second sound level threshold.

Assignees

• Apple Inc

Inventors

• Nicholson Guy C
• Li Wei

Classifications

• H04R1/028

  associated with devices performing functions other than acoustics, e.g. electric candles · CPC title

• H04R3/005

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

• H04R2430/20

  Processing of the output signals of the acoustic transducers of an array for obtaining a desired directivity characteristic (H04R2203/12 takes precedence) · CPC title

• H04N9/79

  Processing of colour television signals in connection with recording · CPC title

• H04R2499/11

  Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's · CPC title