One reason that bar owners may be blasting loud music is because it drives customers to drink more.
Researchers struck a deal with two bars to experiment on young men. The bar owners agreed to let the scientists control the volume for two nights and plant undercover patrons to document the drinking habits of 40 men, age 18 to 25. With louder music, the young men drank a beer three minutes faster, ordered an extra drink and took slightly more gulps.
Loud music may increase an "arousal" state that led the men to drink more. It is also possible that the young men couldn't hear themselves over the music and so, instead of talking, they drank more.