Can you hear me clearly?
Speech intelligibility measures how well speech can be heard and understood in a room. It is closely linked to reverberation time.
Many factors influence speech intelligibility. These include the strength of the speech signal, the direction of the source sound, the level of background noise, the reverberation time of the room and the shape of the room.
The common way of expressing speech intelligibility is the Speech Transmission Index (STI) value on a scale from 0 to 1. In a class room, for example, the level should preferably be above 0.6. A simplified (faster) tool for speech intelligibility is the Rapid Speech Intelligibility Transmission Index (RASTI).