Scottish teachers were yesterday ringing in the New Year with a warning over the noise levels associated with school bells.

Scottish teachers were yesterday ringing in the New Year with a warning over the noise levels associated with school bells.

A teaching union said an increasingly common practice of installing one large bell for the whole school, rather than a series of smaller bells, was risking the hearing of staff and pupils.

And the Scottish Secondary Teachers' Association (SSTA), which represents 9000 secondary teachers north of the border, is appealing for an end to the practice - particularly with the building of new schools.

Jim Docherty, the SSTA's acting general secretary, said all staff should be aware of the potential dangers to hearing of standing too close to a school bell.

"It is clear that many bells have been designed and placed in schools with no thought as to the health of those who happen to be in the proximity of the bells when they sound. Most obviously the effects will be felt by the school staff and pupils," he said.

"It is clear that many bells are installed on the basis of one very loud bell being cheaper than four quieter bells, but this approach is no longer permissible.

"The noise levels experienced by those close to many school bells far exceed any tolerable limits and must constitute a significant danger to the hearing of bystanders."

Mr Docherty said "infrequent exposure" to school bells may be acceptable, but the repetitive and prolonged ringing of very loud bells would eventually cause damage to hearing, with new schools being particular offenders.

"Schools built under public-private partnership arrangements are worse than many older schools," he said.

"There has been a consistent failure to carry out adequate risk assessments, as required by the Health and Safety at Work Act, in many schools. Quite simply many of these schools have seen built on a minimum cost basis.

"School authorities must recognise these concerns where they are expressed and act accordingly before the hearing of staff and students is damaged. The result will inevitably be legal action against the authorities."

However, education campaigners hit out at the plans, calling it "another excuse to spend taxpayers money".

Nick Seaton, chairman of Campaign for Real Education, said: "This seems to be a case of health and safety gone mad. The odd times that the bell rings, between classes, are hardly enough to damage your hearing.

"It's another excuse for more spending of taxpayers' money to change the whole system. It just seems so unnecessary."

Noise output, which is measured in decibels, can damage hearing at a variety of levels depending on the exposure time.

When noise reaches levels above 85 decibels, it can damage the ears, sometimes permanently.

Average conversations are about 60 decibels, alarm clocks and heavy traffic are about 80 decibels and discos or rock concerts are about 115 decibels.

The World Health Organisation says that listening to earphones at 85 decibels or more for over an hour at a time can damage hearing.