Room acoustical parameters

Definition in a cupola hall

Calculated definition in a cupola hall with suspended baffle. The speaker is standing in the light square. In the orange and yellow zones audibility is very good, in the green zones it is good, and in the bluish zones it is not so good.

There is a large number of acoustical parameters for rooms, of which only a few representative examples will be presented here. Their purpose is to describe subjective sound impressions in an objective manner. All room acoustical parameters can be determined from the room impulse response. The room impulse response is the acoustic answer of a room excited by a short bang (to be precise: a Dirac impulse). It is only valid for a specific combination of emitter and receiver positions. Consequently, the acoustical parameters derived from the room impulse response are only valid for the respective positions of the sound source and listener.

The definition is a measure of the intelligibility of a speaker. It indicates how well a speaker can be understood by a listener in a particular seat of an auditorium.

RASTI (Rapid Speech Transmission Index) is a measure that indicates the quality of the transmission of speech. It is used with reference to public address systems as it takes into account the noise from external and internal sources. External sources are, for example, the background noises at a train station. Internal sources are, among other things, the noise of amplifiers and the harmonic distortion of loudspeakers.

Clarity is a comparable measure of the clarity of music. It is used for large rooms like chamber music and concert halls. It is not suitable for the evaluation of the reproduction of music by loudspeakers in a recording studio or listening room.

Lateral fraction and bass ratio:
Lateral fraction is related to the spatial perception of music in a concert hall and indicates how much the listener feels enveloped by the music. The bass ratio describes the warmth of the music.