- choose a lowish, baritone note.
- the other note will be 3 octaves and an augmented fifth above.
A note on attenuation: due to law of RMS, if the two waves had the same amplitude, the high one would be 50 times louder! It needs to be attenuated. Various ways include an rc filter on the speaker amplifier. I chose to manually step the input resistors. The high pitch is attenuated 50dB. It was wrapped in white fur.