Friday 17 September 2010

Flexible Auditorium

On a number of projects MACH Acoustics has been requested to provide acoustic consultancy to achieve flexible acoustics within an auditorium.  Flexible acoustics is the ability to vary the levels of reverberation within a space to achieve a longer reverberation time for a music and short reverberation time for speech.  The table below provides the performance requirements for a range of spaces.

A high reverberation time is required for music, since reverberation will add depth and warmth to the music.  On the other hand, a high level of reverberation will have a detrimental effect on speech intelligibility, meaning that a hall specifically designed for music is not suitable for conferences and drama production.  Designing an auditorium purely for drama and speech often results is a space where music will tend to sound dead and hollow.

The equation below provides the basic Sabines formula for reverberation.  From this equation, it can be seen that to achieve variable levels of reverberation, either the volume of the auditorium and/or the levels of soft treatment within the auditorium, needs to be adjusted.

Due to the impractical nature of adjusting the volume of the auditorium, flexible acoustics is achieved by means of varying the level of soft treatments within a space.  More often than not, this is done by means of employing design options similar to those shown below.

The designs above work by exposing or concealing the acoustics absorption in a space, and therefore varying the acoustics performance of a building.  The key in providing a hall with flexible acoustics is to determine a method of varying the levels of soft treatment.  The auditorium within Slough Libary achieves this very cleverly.  A future blog entry will be added showing how variable acoustics was added to this space.

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