When I start emulation station my speakers are silent. Once I start FBA or any other emu, there is a very clear buzzing from my speakers that continues through the gameplay. Once I drop back out to the frontend the buzzing continues.
Oddly enough the buzzing then only stops when in a command prompt style (i.e the commmand prompt you briefly get when starting a game).
All of this audio is coming from the PI 3.5mm jack – I get none of this via HDMI.
Its a hardware issue with a 3.5 mm jack- isn’t related to retropie. I had the same issue with mine, I just stick with HDMI. There may be ways to quell it with external hardware/sound cards etc. But I never was able to figure it out. Its something that’s been discussed on the raspberry pi forums