Depends on your sound card, but most go up to 96khz, like I said though some of them have a 22khz low pass filter on the input regardless of the 96khz sampling rate (the increased sampling rate is for stereo seperation in the higher frequency ranges) On my card it appears that cut off frequency is pretty sharp, but you'd have to test it yourself. Worse case you're going to at least be able to see the modulation.