Sounding out new schools
Since July 2003 the acoustic design of new school buildings in England and Wales has been subject to the Building Regulations.
The new acoustic criteria which must be met under the regulations are specified in Building Bulletin 93: Acoustic Design of Schools (BB 93), published by the DfES. Prior to 2003 there were no legal requirements relating to a school’s acoustics, although recommendations concerning the acoustic environment in schools had been included in various Building Bulletins over the years.
Speech intelligibility depends upon the level of noise and the amount of reverberation in a room. If the noise levels are too high or a classroom is too reverberant, speech intelligibility is reduced and pupils are unable to hear and understand their teachers.
Sounds being transmitted into a classroom from other areas within a school or from outside also interfere with teaching and may distract pupils. These problems may be exacerbated in schools with open-plan areas. Furthermore, high noise levels and/or too much reverberation make rooms very difficult to speak in, leading to a high risk of voice or throat problems among teachers. In addition to affecting speech intelligibility, poor acoustic conditions in the classroom have a detrimental impact upon children’s learning and development.
A large number of studies carried out worldwide have shown that noise, both from external sources and inside the classroom, can cause annoyance, distraction, and, for younger children, reduced number, letter and word recognition. Noise has also been shown to have a significant negative impact upon children’s academic attainments; for example relationships between noise and SATs scores of inner city primary schools in the UK have been demonstrated.
Furthermore, children with special needs, such as hearing impaired children and children with learning or language difficulties, are known to be particularly vulnerable to the effects of noise and poor acoustics. These children thus require more stringent standards than their mainstream peers.
The criteria specified in BB 93 are those known at the present time to provide satisfactory acoustic conditions for teaching and learning. They were derived after consultation with many experts in the fields of acoustics and school design, including acoustic consultants, education specialists, architects, audiologists and academics.
BB 93 contains performance standards for many areas, including classrooms, within a school. Specifications include background noise levels (indoor ambient noise levels); airborne and impact sound insulation between spaces; reverberation times; sound absorption in circulation spaces; and a speech intelligibility criterion for openplan spaces.
In addition to the regulatory requirements BB 93 contains sections on related areas such as sound insulation, noise control, the design of rooms for speech and music, and the use of amplification systems for pupils with special hearing needs.
Some examples of the requirements (for unoccupied and unfurnished spaces) are as follows: maximum background noise levels of 35 dB(A) for primary and secondary school classrooms, 40 dB(A) for open-plan teaching areas, 30 dB(A) for large lecture rooms and 40 dB(A) for design and technology areas.
Maximum reverberation times are as follows: 0.6 seconds in primary school classrooms, 0.8 seconds in secondary classrooms and one second in music classrooms, libraries and dining rooms. Maximum noise levels and reverberation times for classrooms for specific use by hearing impaired pupils are 30 dB(A) and 0.4 seconds respectively. Acoustic surveys of existing school buildings suggest that acoustic requirements have not had a high priority in the past in school design, with high noise levels and long reverberation times common features of many classrooms. However, concern about classroom acoustics is not a recent development as problems of noise and poor acoustics in schools have been discussed, and guidance given, for more than 70 years.
Nevertheless, many design teams in the past have been reluctant to give acoustics the priority it needs in the overall design of a school. Unfortunately, current architectural fashions for hard reflective surfaces and large open spaces lead to high noise levels and excessive reverberation and continue to contribute to unsuitable acoustic conditions in many new school buildings.
An issue of concern to those involved in school design is the cost of complying with BB 93. In the US it is estimated that compliance with ANSI standard S12.60-2002, which contains similar requirements to those of BB 93, increases the cost of a new school by between 0.5% and 4%.
This is much less than the cost of remedial acoustic treatment following completion of the buildings. However, it is important to also consider the hidden costs to our society of children possibly underachieving in the future, or of teachers’ ill health, as a direct result of poor acoustics in the classroom.
When a new school is planned the acoustic consultant should be an integral member of the planning and design team. It is hoped that in the future, as a result of the publication of Building Bulletin 93, all school buildings will provide a good acoustic environment for teaching and learning so that all children can be educated in schools that are acoustically ‘fit for purpose’.