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...)
The vibrations rattle everything loose cause that's how I work, fast and loose... and accurate. And I'm listening to Disturbed today, because I am disturbed. I work in FAI... I have to be disturbed.