Comparing two sampling rates

This is rather a general question and not specific to MATLAB. I am analyzing speech movements recorded by two systems and One of the instruments is highly utilized in literature and this system is considered a 'gold standard'. Now, I have one more NEW instrument which again measures the speech movement data and I want to validate the data obtained by this with our older instrument. However, the problem is sampling frequency of both the systems is different (1st equipment samples at 200Hz and second at 100Hz). My question is, How valid it is to compare two instruments which measures same variable but uses different sampling frequency to acquire the data?.

Answer 1

[John]

The general answer is that if the sampling frequency is about 10x faster than the highest frequency in your signal, you'll catch everything. Theoretically you only need 2x (although some purists will argue that). I don't know what the frequency range of "speech movement" is, but if it's the same as "speech" I've got bad news. You need to get up to about 30kHz sampling for that. But if the signals you're looking at are on the order of 10Hz or less, then your new sampler will be fine. If it's more like 40Hz or more, you will probably have problems comparing the two samplers.

Answer 2

[Jan]

This question cannot be answered sufficiently based on the provided details. If the measured property (the "speech movement" what ever this is) contains important frequencies above 50 Hz, a 100 Hz sampler cannot determine them. So the achievable quality of the new device depends on the question, if the old gold-standard device has been overdimensioned by a factor of 2 concerning the sampling rate.