Every classroom had a noise defect and newly built rooms, especially in open-plan schools, were worse than old rooms.

The study, by researchers at Heriot-Watt University’s department of building engineering and surveying, recommends teachers should be more aware of the effects of noise and attempt to soften their rooms. Lowered ceilings, wall tiles, curtains, carpets and displays lessen the clatter.

Sharon Airey, research associate, said all rooms suffer from at least one aspect of poor acoustics. Noise can come in from outside the school or classroom or from anything from computers to scraping chairs. “The way classes are taught in little groups generates a lot of noise,” Ms Airey said.

Sound tends to reverberate round rooms with big windows, high ceilings and bare floors. “This helps to slur teachers’ speech and it is difficult to hear clear words. If the background noise is 65 decibels, the teacher has to raise their voice 10-15 decibels above that. The teacher will have to speak at 75-80 decibels to make themselves heard clearly and teachers are complaining of sore throats,” she said. Normal speech is between 40-50 decibels.

Most schools in the study were in Scotland but Ms Airey contrasted a school in Hampshire built three years ago with one built in 1830. “The new school was worse than the old school, especially with open plan,” she said.

With backing from Ecophon, a suspended ceiling company, Ms Airey is to study the psychological effects of noise. Findings so far indicate that it affects stress and concentration levels, memory and children with hearing and visual impairments. Pupils who have colds will also suffer hearing loss, accentuated by poor acoustics.

Ms Airey said schools should have proper acoustics built into them. “Teachers should be more aware of the problem to start with and if they can, do something about it,” she suggested.