Background noise poses adverse effects on speech sounds and affects student learning, especially for children with developmental disabilities. Sound-field and public address amplification systems can help to solve this problem by amplifying speech sounds relative to background noise. This study surveyed school classrooms for children with special needs, and compared the performance of a sound-field and a portable public address system in classroom environments. Unoccupied room noise levels and reverberation times were measured in eight classrooms at four Hong Kong schools for children with special needs. Speech levels in each classroom were measured under three conditions: without amplification, with public address system amplification, and with sound-field amplification. Speech-to-noise ratios were calculated for each condition. Noise and unamplified speech-to-noise ratio values exceeded recommended acoustic standards in all classrooms. When sound-field and public address amplification systems were installed, speech-to-noise ratios improved considerably. When either amplification system was used, a uniform sound-field resulted. The applicability of both types of amplification system and their relative merits in special education classrooms are discussed.[Copyright of International Journal of Disability, Development and Education is the property of Routledge. Full article may be available at the publisher's website: http://dx.doi.org/10.1080/10349120600847508]
