Synchronization of buffered data in multiple microphones

• US 9,111,548 B2
• Filed: 11/05/2014
• Issued: 08/18/2015
• Est. Priority Date: 05/23/2013
• Status: Expired due to Fees

• Current Assignee: Knowles Electronics Llc (Knowles Corporation)
• Original Assignee: Knowles Electronics Llc (Knowles Corporation)
• Inventors: Nandy, Dibyendu, Popper, Robert A., Li, Yang, Qutub, Sarmad, Furst, Claus Erdmann, Thomsen, Henrik
• Primary Examiner(s): Tsang, Fan
• Assistant Examiner(s): Zhao, Eugene
• Application Number:
  US14/533,674
• Publication Number:
  US 20150055799A1
• Time in Patent Office: 286 Days
• Field of Search: 381/26, 381 91- 95, 381/111.700/94, 700/94
• US Class Current: 1/1
• CPC Class Codes: G10L 15/00 Speech recognition G10L17/00 takes precedence
• CPC Class Codes: G10L 2021/02161 Number of inputs available containing the signal or the noise to be suppressed
• CPC Class Codes: G10L 25/78 Detection of presence or absence of voice signals switching of direction of transmission by voice frequency in two-way loud-speaking telephone systems H04M9/10
• CPC Class Codes: H04R 1/08 Mouthpieces; Microphones; Attachments therefor
• CPC Class Codes: H04R 19/005 using semiconductor materials
• CPC Class Codes: H04R 19/04 Microphones H04R19/01 takes precedence
• CPC Class Codes: H04R 2499/11 Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

First analog signals are received from a first microphone, converted into first digital data and stored in a first buffer. A determination is made as to whether voice activity has occurred when voice activity is determined, a voice activity detect signal is sent to an external processor. The external processor responsively provides an exterior clock signal upon receiving the voice activity detect signal. Second analog signals are received from a second microphone, converted into second digital data and stored in a second buffer. The first digital data in the first buffer is not necessarily synchronized in real time with the second digital data in the second buffer. The first digital data from the first buffer and the second digital data from the second buffer is decimated using the external clock to provide decimated output data, the decimated output data having the first digital data and the second digital data aligned in real time.

Claims

1. A method, the method comprising:

receiving first analog signals from a first microphone, converting the first analog signals into first pulse code modulation (PCM) digital data and storing the first PCM digital data in a first buffer using a first microphone internal clock;

receiving a second analog signals from a second microphone according to a second microphone internal clock, converting the second analog signal into second PCM digital data and storing the second PCM digital data in a second buffer;

wherein the first PCM digital data in the first buffer is not synchronized in real time with the second PCM digital data in the second buffer due to the absence of a common clock or other synchronizing signal between the first microphone and the second microphone;

determining whether voice activity has occurred at a first acoustic activity detect (AAD) module based upon the first PCM digital data, and when voice activity is determined, transmitting a voice activity detect signal to an external processor, the external processor responsively providing an exterior clock signal upon receiving the voice activity detect signal;

up-converting the first PCM digital data into first pulse density modulation (PDM) data and the second PCM digital data into second PDM data based upon the exterior clock signal to eliminate a lack of synchronization or time uncertainty between the first PCM data and the second PCM data;

decimating the first PDM data and the second PDM data using the exterior clock signal to provide decimated output pulse code modulation (PCM) data, the decimated output PCM data including a first PCM sample and a second PCM sample, wherein each of the first PCM sample and the second PCM sample begin and end on the same bit clock edge of the exterior clock signal.

2. The method of claim 1, further comprising receiving the exterior clock signal at the first microphone and the second microphone, and synchronizing the operation of the first microphone and the second microphone to the exterior clock signal.

3. The method of claim 1, further comprising subsequent to decimating the first PDM digital data and decimating the second PDM digital data, performing two channel voice signal enhancement with the decimated output data from the first microphone and the second microphone.

4. The method in claim 1, wherein the second microphone and not the first microphone is kept in a low power or sleep mode until the exterior clock signal is applied by the external processor.

5. The method of claim 1 wherein the external processor includes a decimator and the decimator is configured to decimate two or more channels using the same clock, and same PCM sample synchronization signal or Word Strobe (WS).

6. The method of claim 1, wherein the first microphone, the second microphone, and a multiplicity of additional microphones are connected via a common clock line and multiple serial PDM data lines to the external processor.

7. The method in claim 1, wherein the first microphone includes a first buffer and the first microphone is kept in a sensing mode with the first AAD module and first buffer being active.

8. The method in claim 1, wherein the second microphone and any additional microphones and not the first microphone is kept in a low power or sleep mode until the exterior clock signal is applied by the external processor.

9. The method of claim 1, further comprising subsequent to decimating the PDM digital data from the first microphone, the second microphone, and a multiplicity of additional microphones, performing multiple channel voice signal enhancement with the first PCM sample and the second PCM sample.

10. An apparatus, the apparatus comprising:

an external processor;

a first buffer coupled to the external processor;

a second buffer coupled to the external processor;

a first analog-to-digital converter coupled to the first buffer, the first analog-to-digital converter configured to receive first analog signals from a first microphone, convert the first analog signals into first pulse code modulation (PCM) digital data and store the first pulse code modulation (PCM) digital data in a first buffer;

a first acoustic activity detect (AAD) module coupled to the first analog-to-digital converter, the first acoustic activity detect module configured to determine whether voice activity has occurred based upon the first pulse code modulation (PCM) digital data, and when voice activity is determined, transmit a voice activity detect signal to the external processor, the external processor responsively providing an exterior clock signal upon receiving the voice activity detect signal;

a second analog-to-digital converter coupled to the second buffer, the second analog-to-digital converter configured to receive a second analog signals from a second microphone according to the exterior clock signal, convert the second analog signals into second pulse code modulation (PCM) digital data and store the second digital data in a second buffer;

wherein the first PCM digital data in the first buffer is not synchronized in real time with the second PCM digital data in the second buffer;

wherein the first buffer, the first analog-to-digital converter, and the first acoustic activity detect module are disposed at a first microphone, and wherein the second buffer and the second analog-to-digital converter are disposed at a second microphone;

wherein a first up-converter or interpolator is coupled to the first buffer, and a second up-converter or interpolator is coupled to the second buffer, the first up-converter and the second up-converter are configured to up-convert the first PCM digital data into first pulse density modulation (PDM) data and up-convert the second PCM digital data into second pulse density modulation (PDM) data based upon the exterior clock signal to eliminate a lack of synchronization or time uncertainty between the first PCM digital data in the first buffer and the second PCM digital data in the second buffer;

wherein the first analog-to-digital converter, the first buffer, the first acoustic activity detect module, and the first up-converter or interpolator are disposed at a first microphone, and wherein the second analog-to-digital converter, the second buffer and the second up-converter or interpolator are disposed at a second microphone;

wherein the external processor is configured to decimate the first PDM data from the first buffer in the first microphone and the second PDM data from the second buffer in the second microphone using the exterior clock signal to provide a first decimated PCM sample and a second decimated PCM sample, wherein each of the first decimated PCM sample and the second decimated PCM sample begin and end on the same bit clock edge of the exterior clock signal.

11. The apparatus of claim 10, wherein the exterior clock signal is received at the first microphone and the second microphone, and the operation of the first microphone and the second microphone is synchronized to the exterior clock signal.

12. The apparatus of claim 10, further comprising subsequent to decimating the first PDM digital data and the second PDM digital data, performing two channel voice signal enhancement with the first decimated PCM sample and the second decimated PCM sample from the first microphone and the second microphone.

13. The apparatus of claim 10, wherein the second microphone and not the first microphone are kept in a low power sleep mode until the exterior clock signal is applied by the external processor.

14. The apparatus of claim 10, wherein the external processor includes a decimator and the decimator is configured to decimate two or more channels using the same clock, and same sample synchronization signal or Word Strobe (WS).

15. The apparatus of claim 10, wherein the first microphone, the second microphone, and a multiplicity of additional microphones are connected via a common clock line and multiple serial PDM data lines to the external processor.

16. The apparatus in claim 10, wherein the first microphone is kept in sensing mode with the first AAD module and first buffer being active.

17. The apparatus of claim 10, wherein the second microphone and any additional microphones and not the first microphone are kept in a low power sleep mode until the exterior clock signal is applied by the external processor.

18. The apparatus in claim 10, further comprising subsequent to decimating the digital data from the first microphone, the second microphone, and a multiplicity of additional microphones, performing multiple channel voice signal enhancement with the first PCM sample and the second PCM sample.