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Batteries playing music?! Answered

I have built a plasma speaker and I am using it for my science fair and while I was listening to my speaker I realized that sound was coming from somewhere besides the speaker(arc). I disconnected the arc and it was coming from the batteries! Is there any way to prevent the batteries from playing the music as well? Is it feedback? I'd like the science fair judges to only hear the arc, thank you.

Also I used this guys instructible


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9 years ago

What sort of battery are you running from? If it's a lead / acid accumulator then it's most likely the plates flexing very slightly with the current peaks / troughs of the switching frequency.
Even if it's not, try upping the capacitor across the circuit input.  Replace that 200uF with something like 2200uf.  This will smooth out the draw from the battery and hopefully stop it singing.