What carrier frequency or pitch to use in your isochronic tones?
Practically any frequency in the audible range can be used (20hz to 16000hz). That's a lot to choose from!
From my experience, what's pleasant to the ear is to use a carrier frequency which is a harmonic of the isochronic tone. The harmonic frequency is calculated as:
isochronic tone X n, where n is the no. of harmonic
As an example, if your isochronic tone frequency is 10hz (alpha range), the harmonic frequencies are:
10hz X 2 = 20hz (second harmonic)
10hz X 3 = 30hz (third harmonic)
10hz X 4 = 40hz (fourth harmonic)
.....and so on
20, 30, 40, 50, 60....190, 200,....
You may first want to experiment with a carrier pitch that you would like. There are people who prefer the low frequency range and others prefer a higher pitch. Generate different tones using the audacity software mentioned in the square waves project so that you can 'preview' the carrier frequency and decide what seems nice for you.
Once you find the carrier frequency that's nice to hear for you, you can then create a more pleasant isochronic tone.
The next project will be on creating ramps. If you're targetting an isochronic tone for a theta brainwave entrainment, it's best to start in the alpha and ramp down to your target theta frequency.