Do you have the correct pull-up resistor at the output of the LM393?? Backing up, for the inputs to the comparator, one must be the audio signal centered at about half of the reference voltage, and the reference voltage should be about half of the triangle wave max value.. So there are four voltages that need to be set before you can expect it to work at all.
Also, if you can hear the triangle wave frequency it is much too low.

 

Can I advise isopropyl on Q-tips ear scwabs?

The PWM frequency for a class "D" audio amplifier should be well above the highest frequency amplified. That is rather basic.