Home Cinema Seating Area and Absorption Properties - October 21st, 2008
The purpose of most medium to large dedicated home cinema installations is to accommodate a large number of spectators, enabling them to watch movies from the comfort of their own home. The important acoustical properties are therefore those which are present when the home cinema rooms are occupied, or at least partially occupied. These properties are largely determined by the audience itself, especially by the sound absorption affected by the people or, strictly speaking, by their clothing.
The absorption affected by an audience in a home cinema room is due mainly to people’s clothing and its porosity. Since clothing is not usually very thick, the absorption is considerable only at medium and high frequencies; in the range of low frequencies it is relatively small. Since people’s clothing differs from individual to individual, only average values of the audience absorption are available and it is quite possible that these values are changing with the passage of time according to changing fashion or season.
Furthermore, home cinema seating area’ s absorption depends on the kind of seats and their arrangement, on the occupancy density, etc. Therefore it is not surprising that there are considerable differences in the data on audience and cinema seating absorption which have been given by different authors.
When people are seated close together in a dedicated home cinema room, it seems to be more correct to relate the absorption of audience and areas covered with equal seats, not to the numbers of ‘objects’ but to their area, since this figure seems to be less dependent on the density of cinema seats or listeners. It has been known for a long time that an audience does not only absorb the impinging sound waves, it reduces the reverberation time of the home cinema room, and also attenuates the sound waves propagating parallel to the audience. About the same holds for unoccupied cinema seats.
Listening conditions will be impaired, however, if the sight lines from the listeners to the home cinema speakers are obscured by the heads of other listeners sitting in front of them. Therefore it is important that the home cinema seats are arranged in such a way that the listeners are freely exposed to the direct sound and the reflections arriving from the side walls, allowing for a proper experience of their installed home cinema systems.