Horrible. I actually tried applying image compression to sounds over a decade ago (was still in school, did that for Jugend forscht). I used a Fourier transform to generate image sections of a specific window of samples and used that. In hindsight, perhaps just treating the waveform as image data may have been better. The idea behind what I did was to see whether a spectrogram can be compressed well, considering that there's lots of repetition and blank space usually.

In any case, JPEG murders pretty much everything in thag representation.