Two thirds of UK call centres fail to protect their workers against hearing damage from noise, a report warns.
Call centre staff 'should be protected against hearing problems'
Experts will tell an acoustic safety conference in Glasgow many of the 900,000 call centre staff are at risk.
They are set to say increasing numbers of injuries and illnesses are being caused by acoustic shock and other noise related hazards.
Over 700 people have so far suffered acoustic shock, with the compensation paid out so far totalling £2.5m.
Around 300 further cases are pending, according to the Acoustic Safety Programme, an independent body which aims to protect the hearing of call centre workers.
Acoustic shocks are defined as "any temporary or permanent disturbance of the functioning of the ear, or of the nervous system, which may be caused to the user of a telephone earphone by a sudden sharp rise in the acoustic pressure produced by it".
The sound could be a whistle, a bleep - or any unexpected noise.
Experts suggest there are many more people who have experienced acoustic shock but do not realise it.
It warns that, while some organisations are acting to safeguard the hearing of their staff, the vast majority are not.
Call centres can introduce equipment such as headphones which extract any potential causes of acoustic shock to protect the worker's hearing.
There should also be measures such as raising awareness of the problem and good incident reporting that the Health and Safety Executive recommend should be in place.
Chris Atwell, operations director for the Acoustic Safety Programme, said: "It can be a debilitating occurrence for a call centre worker.
"They can develop permanent damage to their hearing."
Dr Mark Downs, executive director of technology and enterprise for the Royal National Institute for the Deaf, said: "Acoustic shock is not the same as noise-induced hearing loss and is believed to occur at sound pressure levels below those which present an immediate risk to hearing damage.
"It is still a relatively un-researched condition and RNID welcomes public debate on the issue."