My application uses a MEMS microphone amplified by an AD8429 instrumentation amplifier with a bandpass filter to acquire signals. The phenomena I'm measuring occurs at a specific frequency and so I use I/Q demodulation on a 2-second time series sampled at ~16 kHz to extract that information.
I'd like to go one step further and improve SNR by using multiple microphones - six to eight, in fact. My question is how to best approach averaging the signals. One option would be to measure all microphones simultaneously with a simultaneous-sampling ADC like the AD7606 and average the signals after acquisition. The other option would be to connect the outputs of the instrumentation amplifiers to a unity-gain averaging amplifier arrangement (or something similar) and let the hardware do the averaging. The entire arrangement - microphones, amplifiers, and ADC - would be calibrated as if it were a single sensor.
I have two questions:
- Which is the preferable method for averaging, hardware or software?
- If it's hardware, what circuit should I investigate to perform this?
I'm leaning towards software averaging at the moment. I'm worried about constructing 8 truly identical inputs for the averaging amplifier (resistor choice being what it is). Any guidance is appreciated.