The Institute of Hearing Research (IHR) in Glasgow estimates there are about 7.5 million people with various degrees of hearing loss in the UK.
It says about 3.8 million can no longer detect sounds in their better ear below 35 decibels, up from 3.4 million two decades ago. This level of noise is the equivalent to a whisper.
Charities are warning music lovers to put the volume down on their earphones or risk permanent hearing loss.
Scientists say legislation in 1989 and 2005 to limit exposure to loud noises in the workplace will lead to a drop in the number of people suffering hearing loss.But it is likely there will be a rise among the iPod generation, who are often exposed to loud music for long periods.
Dr Michael Ackeroyd, who leads the IHR's Scottish branch, said: "As the population ages, the number with hearing loss is going up. It's far easier to listen to music loudly and for longer periods than 30 years ago."