Provides a simple calculation procedure for estimating the sound level of a fire alarm at any position in a building. The British Standard BS 5839 Part 1 1980, 'Fire detection and alarm systems in buildings' gives for the first time a stated (and hence measurable) minimum sound level that fire alarm sounders should achieve at any occupiable point in a building. A level of 65 dBA or 5 dBA above the background noise, is required. The subject of acoustics is reviewed. Experimental results of sounder tests undertaken at BSRIA are presented. Sound reduction indices for different building structures are given. Worked examples are presented for sound levels at desks in offices and classrooms.