For me its headphones unless I like what is playing in the shop (we have speakers in FAI connected to the shop speakers with our own volume control. I like hard rock/metal (Disturbed, Korn, Volbeat, Slipknot, ect...)
Some of my favorites:
In This Moment, Slayer, Five Finger, Disturbed, Pantera, Seether, Saliva, Mastodon, Theory of a Deadman, Skillet, Stitched Up Heart, Nonpoint, Metallica, Halestorm, Oh and of course Spice Girls, NOT. No metal head can really like the Spice Girls!