Machine learning in audio?
I think that resources about speech processing would be a good introduction to audio files manipulation for machine learning in general.

For a broader introduction to audio,
Machine Learning for Audio, Image and Video Analysis: Theory and Applications, Reviews
Book by Alessandro Vinciarelli and Francesco Camastra could be a good read.

Also, check out some blogs like this one: https://www.analyticsvidhya.com/blog/2018/01/10-audio-processing-projects-applications/ (as you mention deep learning in the tags) that can give a good introduction with some hands-on experience.