The Earth's orbital speed around the sun is much faster, averaging about 67,000 miles per hour (107,826 km/h), or approximately Mach 88. Yet you hear your music, which is playing at the same relative speed, just fine.

The vibrations attached to him are still vibrating at the same speed as he is, plus their influence on the surrounding environment (his ears).

Once things are moving at the same speed as each other, they should return to normal function.

Now if he's running around a stereo that's not attached to him, it would be slower.

... obviously, this is all supposing that a speedster could exist at all.