Dear Sound Design community,
we are doing research in bioacoustics and need to determine the make and specifications of microphone elements inside digital voice recoerders that were used in the past, especially with respect to their signal-to-noise ratio.
We have used the Olympus DM-620 and Olympus DS-40 digital voice recorders.
Different information requests to Olympus in the USA and Germany did not lead to any sharing. Olympus does not disclose that information, and it also commonplace for the other major manufacturers, which at best report microphone sensitivity.
Their product manuals say:
DM620 has a 40 Hz to 23 kHz frequency response at the highest sampling frequency and depth (48kHz 16 bit)
DS40 has a 50 to 19 kHz frequency response at the highest quality recording setting (XQ mode)
So we disassembled the units, and we found circular microphones with solder pads, with numbers etched onto the microphone elements, and we measured their height and diameters to find out whether we could reasonably estimate their SnR from similarly specified microphones with this Digikey data base: http://www.digikey.com/products/en/audio-products/microphones/158/
So far, the numbers etched onto the microphone elements did not yield any result. But we can guess the SnR based on similar microphones in that database, unfortunately that may not be a very clean approach.
Our questions are:
do Olympus manufacture their own microphone elements, so that specifications are entirely inaccessible?
Does it make sense to assume that microphones of a similar type (we assume it's an electret condenser), frequency response, height and diameter, will have a similar SnR?
How could we measure the SNR of these microphones?
If by any chance you simply know the SnR of these microphones, that would be the simplest answer.
Here are pictures of the microphone elements: http://imgur.com/a/b711Q Sorry that I cannot post more links due to too little reputation.