Two generated tones creates a side tone - how to avoid the side tone I'm trying to create two tones at different frequencies. So I have one tone at 15000 Hz and one at 15400 Hz using Audacity. The problem i'm running into is there is a third tone created at a much lower frequency I can tell exists from both my ears and a spectrogram.

How can I get rid of the lower tone? Where does it come from? I only have two tracks
I have tried the following:


Launch Audacity.
Generate a 15000 Hz tone in the track created by default.
Add a new track.
Generate a 15400 Hz tone in the new track.


A lower frequency tone appears during playback.

The reason is that both tracks have high levels, so their sum exceeds 1.0; and Audacity applies clipping or limiting. This non-linear operation is what creates the overtone.

Simply decrease the level of both tracks to -6dB (or use an amplitude of 0.5 during signal generation) to make the overtone disappear.