If you have a hard time hearing conversation at a bar, it may not be because of the noise, a study suggests.

Alcohol, UK researchers found, seems to temporarily drain a person's hearing - particularly when it comes to discerning the sounds of conversation.

In a study of 30 healthy volunteers, they found that as participants drank their hearing became less acute.

Lower-frequency hearing, which is necessary for discerning speech, suffered the most, the researchers report in the online journal BMC Ear, Nose and Throat Disorders.

It is a "well-observed phenomenon" that alcohol seems to build people's tolerance to loud noise, according to the study authors, led by Tahwinder Upile of the University College London Hospitals.

But bouts of so-called "cocktail party deafness" may not result from the noisy drinking environment alone, the researchers note.