Sampling at low frequencies

Question

I already wrote this question before, but they did not answer it. Maybe I was not clear enough, so let me rephrase:

As you know, when you sample a signal at a specific sampling rate, any frequency that exceeds half the sampling rate becomes an alias. To avoid this, you need to transmit the signal (either in analog form or in digital form, selected at a higher speed) through the appropriate low-pass filter.

Now, in my case, I am using Windows waveIn functions to collect mic input at a specific speed. Since waveIn functions work with any sampling rate that I provide it, and not at harsh predetermined speeds, I really don’t know if the sound card really samples at that speed or if it samples at a predetermined speed, and the system “converts” it at my requested rate. Actually, I don’t care ...

What bothers me when I dial, say, 8 kHz, whether the sound card or the system performs low-pass filtering (either analog on the sound card or digital, which is then limited by some maximum sampling speed supported by the sound card), so I won’t get alias frequencies at my input.

Or maybe I should try with the highest sampling rate and filter the frequencies myself?

Answer 1

I think you would use a very bad sound card if you hadn't used LPF before trying out the signal. I would not worry about that! You can always check by transmitting a 10 kHz tone and see if it goes through an alias or not.

EDIT: 44,1 48 - , waveIn LPF . . , , , .