Comment by nullc
14 years ago
Alas, they don't— you can easily demonstrate this for yourself. Startup an audio editor and generate tones at 25k and 28k (make sure you can't hear them— otherwise you have severe distortion screwing up your test) then play both at once. You will not hear a 3kHz tone.
The tone you get from an acoustic beat is not a real tone— it's a perceptual quark that requires you to be able to hear the tones in the first place.
I tried this in Audacity, with the project set to 96kHz and two tones at 25kHz and 28kHz. I couldn't hear either of the tones individually, but I could hear a tone when played together. This is on Windows 7 with the sound card configured for 24-bit/48kHz. Am I running into resampling artifacts somewhere in the chain?
EDIT: it turns out Audacity won't generate a tone above 20kHz (the UI accepts the value, but when you reopen it the value has been rounded down), so both of my generated tones were actually 20kHz.
I tried this with 19kHz and 20kHz. Couldn't hear any of them on their own, but very clearly together.
EDIT: You can generate higher than 20kHz by increasing the pitch of a tone lower than 20kHz. Upon doing this, I could hear 24kHz and 26kHz together.