Synchronization of buffered data in multiple microphones

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.