Can children always hear what their teachers are saying? You might think this is a question for those with impaired hearing, but the problem of poor acoustics in the class is a widespread one.
Last summer the Department for Education and Skills issued Building Bulletin 93 (BB93), which reports on acoustics in the design of schools and sets higher standards for new school buildings and refurbishments. The reason for the report is the growing evidence of the impact of background noise on children's development in school.
Simon Blake, an educational audiologist with Leicestershire county council, says: "Over the years we have become more concerned with the impact of poor classroom acoustics on the progress of children in school.
"Noisy classrooms make speech perceptions difficult - not only for those who need hearing aids, but for everyone, including the teacher."
In his experience, old school buildings are the noisiest.
"They are often harsh environments with wooden floors and high ceilings," he says.
He says even the most ancient classrooms can be improved so that teachers don't have to shout.
Mr Blake, who has an MA in acoustics, points to the Disability Discrimination Act and special needs regulations that will put pressure on schools to ensure that poor classroom acoustics are not hindering pupils'
Reverberation - the time it takes for a sound to decay or die - is the main problem, he says. With lots of high walls, bare floors and thin walls, sounds bounce off these surfaces, and then keep bouncing, making it harder to hear what is being said.
Terry King from Burmatex, a carpet firm which has produced a leaflet for schools on accoustics, says: "Younger children are vulnerable because excess noise hinders learning at an early stage.
"It has also been shown that older and less able children are most affected by external noise such as traffic, as well as ambient noise from ventilation, lighting equipment and the classroom itself."
But it is not only the children who suffer from noise pollution.
"Noise-related health problems for teachers such as throat-related illness caused through trying to make oneself heard, as well as stress, are cited by more than 90 per cent of teachers reporting health problems," says Mr King.
He points to research by Professors Shield and Dockrell at South Bank university and London university's Institute of Education which suggests noise is "a clear and debilitating factor in long-term memory, attention span and reading ability".
The new rules have definitely started to focus minds.
"Teachers are beginning to realise that if students can actually hear what is being said, in an often noisy environment like a school gym or assembly hall, then they are more likely to learn," says Brian Harris, a director of Eckel Noise Control Technologies.
He adds: "Reverberation can prolong or distort original sound components.
Speech intelligibility is compromised when a soft vocal element is masked by the reflected sound of a preceding louder element. Reverberation also amplifies background noise."
So how can reverberation be reduced?
Mr Blake says: "There are often very simple measures such as carpeting and curtains."
More high-tech solutions include sound field systems (microphones and speakers) but these are not cheap.
Another approach provided by Eckel, is to install materials which absorb sound into existing walls and ceilings. Seals on doors and windows can also help to reduce noise from outside.
The first step, says Mr Harris, should be a noise survey to measure background levels.
"Many older schools built with high concrete ceilings and equipped with individual room heating and ventilation units will not meet recommended standards without modification," he says.
A noise survey, often available free of charge, will measure background levels, noise isolation and reverberation characteristics in a room.
Given that schools often have to pay for acoustic improvements out of their own budgets, cost is a big factor in improving sound quality in the classroom. So a simple carpet could be the answer.
"Carpet has been proven to help dampen and reduce the impact sound in the school environment," says Mr King.
But a balance needs to be struck. For example, an expensive thick-pile carpet might have excellent acoustic properties but be totally impractical for a Year 8 art lesson. One option is to go for high-quality backing.
Mr King says: "Our carpets and carpet tiles have a thick bitumen backing which has high acoustic properties." However schools respond to BB93, it will be their responsibility to make suitable purchases. "There is a lot of poor advice being given," says Mr King. "The key is to have your school building noise-tested and to work out what can be done within a restricted budget."
For new schools, BB93 is not an option - it is obligatory, so local authorities must sit up and take notice.
For more on BB93, see www.bb93.co.uk
Thanks to staff and pupils at Bradford Grammar School for co-operation on pictures