Lessons learned from acoustic testing in schools in the south-west of England

摘要

Findings from post-construction acoustic tests in over thirty schools in England have been collated to reveal common causes of non-compliance with Building Bulletin 93. A range of accommodation has been tested, including primary and secondary schools, and music and workshop facilities. Noise ingress through window openings was found to be predicted reasonably accurately by assuming a hole offering no attenuation. With appropriate levels of acoustic attenuation, quiet levels could be achieved from mechanical ventilation services. Wall or ceiling-mounted fans within spaces were ubiquitously found to exceed maximum noise levels for teaching spaces. The sound attenuation offered by both masonry and stud wall constructions was found to be variable. Many cases of severe degradation were traced to unsealed service penetrations and poor ceiling at the partition head, particularly above false ceilings. Floor constructions fared better, possibly because there is less scope for such concealment. Investigation of open windows as a flanking path between rooms showed that significant degradation could be expected if the partition R_(W) exceeded 50 dB. Except for carpeted rooms with low ceilings, an additional highly acoustically absorbing surface will be needed to control reverberation in classrooms. In larger spaces, including school halls, it is important to accurately predict the reverberation time of an unfurnished space, since they may be used in such a condition. The Sabine formula then significantly under-predicts reverberation, particularly if a highly sound absorbing ceiling is specified. Ray tracing has been found to be far more accurate and is recommended for such spaces.