| Speech intelligibility Speech intelligibility defines how clear speech communication is, and it is directly related to the reverberation time and the background noise level in a room. Good speech intelligbility is required in e.g. class rooms, lecture theaters, etc. To achieve this surfaces with different absorption characteristics can be placed in different areas of the room. The below illustration is an example of acoustic regulation in a lecture theatre where a reflecting area is integrated in the ceiling in order to reinforce the sound level to the audience. A sound absorbing ceiling is installed in the remaining ceiling area and on the back wall. The reflecting area is about 10% of the total ceiling.  Speech intelligibility can be measured in any room and analysed using computer software. It can be quantified by the Rapid Speech Transmission Index (RASTI) value which is quoted between 0 and 1. the below figure shows how the RASTI value compares with a subjective speech intelligibility scale.  |
