Of all the things your smartphone can do, playing music is one of the least demanding. Listening to a song puts very little strain on the CPU, doesn’t require GPS, and often doesn’t require wi-fi (so long as the music files are stored on your phone). Simple physics says that listening to louder music should use up battery faster, but I still wanted to know exactly how much.
Source: Gizmodo – Does Playing Loud Music Kill Your Battery Faster?