Reducing seat dip attenuation

Strategies fur reducing seat dip attenuation in concert halls are considered. It is shown that the dip is established 4 ms after the direct sound from the stage arrives at the listener. Sound scattered from the seats and floor is the main cause of the dip. By controlling these very early reflections the attenuation can be reduced to below its subjective threshold. With this in mind, changes to the shape and impedance of the seats and floor are trialed using a boundary element model and a physical scale model. It is found that the seat dip effect can be rendered inaudible by introducing a l-m pit under the seats. Smaller improvements are produced by changing the impedance of the seat squab. (C) 2000 Acoustical Society of America

Response to "comment on 'reducing seat dip attenuation'" J. Acoust. Soc. Am. 110, 1260 (2001)

This letter responds to Klepper's comments [J. Acoust. Soc. Am. 110, 1260 (2001)] on the subject paper, which is concerned with ameliorating seat dip attenuation in auditoria by introducing a pit under the seats. Klepper asks what the effect of the pit will be on seat absorption and reverberation times. A little evidence is presented to support the idea that low-frequency absorption in an auditorium will increase with a pit. It is further speculated that reverberation times could be predicted by using a coupled space model. Klepper's suggestion of an experiment to answer his questions is supported. (C) 2001 Acoustical Society of America

Predicting theater chair absorption from reverberation chamber measurements - comment

The relationship between the measured acoustic absorption coefficient of an array of theater chairs and the ratio of the perimeter length to plan area of the array is considered. It is shown that the linear relationship measured by Bradley in a reverberation chamber and reported in ''Predicting theater chair absorption from reverberation chamber measurements'' [J. Acoust. Soc. Am. 91, 1514-1524 (1992)] is to be expected from simple theory. This means that any nonlinear influence of diffracted energy on the relationship is small. Bradley is also unduly harsh on the usefulness of a chair absorption measurement method involving screens. A sample result is given, showing that this method can predict in-situ theater chair absorption with reasonable accuracy