DIGITAL DUAL MICROPHONE MODULE WITH INTELLIGENT CROSS FADING

• US 20120106753A1
• Filed: 11/02/2010
• Published: 05/03/2012
• Est. Priority Date: 11/02/2010
• Status: Active Grant

• Current Assignee: Bosch Security Systems Incorporated (Robert Bosch GmbH), Robert Bosch GmbH
• Original Assignee: Bosch Security Systems Incorporated (Robert Bosch GmbH), Robert Bosch GmbH
• Inventors: Zehnder, Darcy, Aly-Youssef, Talal, Theverapperuma, Lalin S., Parker, Steve
• Granted Patent: US 8,577,057 B2
• Time in Patent Office: Days
• US Class Current: 381/92
• 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 21/0208 Noise filtering
• CPC Class Codes: H04R 2201/107 Monophonic and stereophonic headphones with microphone for two-way hands free communication
• CPC Class Codes: H04R 2410/05 Noise reduction with a separate noise microphone
• CPC Class Codes: H04R 2430/01 Aspects of volume control, not necessarily automatic, in sound systems
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

A method of operating a microphone system includes providing first and second microphones associated with a same human speaker. An analog ambient noise signal is received from the first microphone. An analog speech signal is received from the second microphone. The analog ambient noise signal is converted into a digital ambient noise signal. The analog speech signal is converted into a digital speech signal. Digital noise cancellation is performed on the digital speech signal dependent upon the digital ambient noise signal. The digital noise cancellation is performed by digital circuitry. The noise canceled digital speech signal is inputted into an intercom system. A low power condition of the microphone system and/or a failure of the digital circuitry is sensed. In response to the sensing step, an analog-based intercom signal is inputted into the intercom system. The analog-based intercom signal is dependent on the analog speech signal and substantially independent of the analog ambient noise signal. The analog-based intercom signal is inputted into the intercom system without noise cancellation having been performed on the analog-based intercom signal.

Claims

1. A method of operating a microphone system, comprising the steps of:

providing first and second microphones associated with a same human speaker;

receiving an analog first signal from the first microphone;

receiving an analog second signal from the second microphone;

converting the analog first signal into a digital first signal;

converting the analog second signal into a digital second signal;

performing digital noise cancellation on the digital second signal dependent upon the digital first signal, the digital noise cancellation being performed by digital circuitry;

inputting the noise canceled digital second signal into an intercom system;

sensing a low power condition of the microphone system and/or a failure of the digital circuitry; and

in response to the sensing step, inputting an analog-based intercom signal into the intercom system, the analog-based intercom signal being dependent on the analog second signal and substantially independent of the analog first signal, the analog-based intercom signal being input into the intercom system without noise cancellation having been performed on the analog-based intercom signal.

2. The method of claim 1 wherein, upon startup of the system, the analog-based intercom signal is inputted into the intercom system until the digital circuitry is operable.

3. The method of claim 1 wherein the providing step includes providing the first and second microphones on opposite ends of a same boom.

4. The method of claim 1 further comprising providing a push to talk button associated with the second microphone, wherein, upon each instance of the push to talk button being pushed, the analog-based intercom signal is inputted into the intercom system until the digital circuitry is operable.

5. The method of claim 1 wherein the first and second microphones are less than one foot apart.

6. The method of claim 1 wherein the step of performing digital noise cancellation includes subtracting the digital first signal from the digital second signal.

7. The method of claim 6 wherein, before the digital noise cancellation is performed, the method includes the further step of adjusting a volume of the digital first signal and/or the digital second signal such that the volume of the digital first signal is approximately equal to a noise component of the digital second signal.

8. A method of operating a microphone system, comprising the steps of:

providing first and second microphones associated with a same human speaker;

receiving an analog ambient noise signal from the first microphone;

receiving an analog speech signal from the second microphone;

converting the analog ambient noise signal into a digital ambient noise signal;

converting the analog speech signal into a digital speech signal;

performing digital noise cancellation on the digital speech signal dependent upon the digital ambient noise signal, the digital noise cancellation being performed by digital circuitry;

inputting the noise canceled digital speech signal into an intercom system;

sensing a need to provide input to the intercom system without using the digital circuitry;

in response to the sensing step, ascertaining when a volume level of the noise canceled digital speech signal is below a threshold level; and

in response to the ascertaining step;

performing cross-fading from the noise canceled digital speech signal to an analog-based signal that is dependent on the analog speech signal and substantially independent of the analog ambient noise signal, the cross-fading producing a cross-faded intercom signal; and

inputting the cross-faded intercom signal into the intercom system.

9. The method of claim 8 wherein, upon startup of the system, an analog-based intercom signal is inputted into the intercom system until the digital circuitry is operable.

10. The method of claim 8 wherein the step of performing cross-fading includes gradually increasing an analog-based signal component and correspondingly decreasing a noise canceled digital speech signal component of the cross-faded intercom signal.

11. The method of claim 8 further comprising providing a push to talk button associated with the second microphone, wherein, upon each instance of the push to talk button being pushed, an analog-based intercom signal is inputted into the intercom system until the digital circuitry is operable.

12. The method of claim 8 wherein the first and second microphones are less than one foot apart.

13. The method of claim 8 wherein the step of performing digital noise cancellation includes subtracting the digital ambient noise signal from the digital speech signal.

14. The method of claim 13 wherein, before the digital noise cancellation is performed, the method includes the further step of adjusting a volume of the digital ambient noise signal and/or the digital speech signal such that the volume of the digital ambient noise signal is approximately equal to a noise component of the digital speech signal.

15. A method of operating a microphone system, comprising the steps of:

providing first and second microphones associated with a same human speaker;

upon startup of the system;

receiving an analog ambient noise signal from the first microphone;

receiving an analog speech signal from the second microphone;

inputting an analog-based intercom signal into an intercom system dependent on the analog speech signal and substantially independent of the analog ambient noise signal, the analog-based intercom signal being input into the intercom system without noise cancellation having been performed on the analog-based intercom signal; and

initializing digital circuitry;

after the startup has been completed and the digital circuitry has been initialized;

converting the analog ambient noise signal into a digital ambient noise signal;

converting the analog speech signal into a digital speech signal;

performing digital noise cancellation on the digital speech signal dependent upon the digital ambient noise signal, the digital noise cancellation being performed by the digital circuitry; and

inputting the noise canceled digital speech signal into the intercom system.

16. The method of claim 15 comprising the further steps of:

sensing a low power condition of the microphone system and/or a failure of the digital circuitry; and

in response to the sensing step, re-inputting the analog-based intercom signal into the intercom system dependent on the analog speech signal and substantially independent of the analog ambient noise signal, the analog-based intercom signal being input into the intercom system without noise cancellation having been performed on the analog-based intercom signal.

17. The method of claim 15 wherein the providing step includes providing the first and second microphones on opposite ends of a same boom, less than one foot apart.

18. The method of claim 15 further comprising providing a push to talk button associated with the second microphone, wherein, upon each instance of the push to talk button being pushed, the analog-based intercom signal is inputted into the intercom system until the digital circuitry is operable.

19. The method of claim 15 wherein the step of performing digital noise cancellation includes subtracting the digital ambient noise signal from the digital speech signal.

20. The method of claim 19 wherein, before the digital noise cancellation is performed, the method includes the further step of adjusting a volume of the digital ambient noise signal and/or the digital speech signal such that the volume of the digital ambient noise signal is approximately equal to a noise component of the digital speech signal.