Beats from Two Speakers
Two speakers with separate audio oscillators produce beats.
The Pasco function generators default to 1kHz when they are turned on. Slowly turn the frequency adjustment knob on one generator (leaving the other at 1 kHz) to produce an audible beat frequency.
Power the generator off and on again to return it to the 1 kHz default frequency. While the two generators are at the same frequency, they are out of phase (which the human ear is unable to distinguish).