Click here to purchase the entire book in PDF format. Frequency Range We said earlier that the limits on human frequency response are about 20 Hz in the low frequency range and 20 kHz in the upper end. This has been disputed recently by some people who say that, even though tests show that you cannot hear a single sine wave at, say, 25 kHz, you are able to perceive the effects a 25 kHz harmonic would have on the timbre of a violin. This subject provides audio people with something to argue about when they've agreed about everything else... It's also important to point out that your hearing doesn't have a flat frequency response from 20 Hz up to 20 kHz and then stop at 20,001 Hz... As we'll see later, it's actually a little more complicated than that.