Lab Task 5: Concert hall design
Time slot: 08W14 - 08W15 || Published: April 14th, 2008
Equipment
Purpose
In this lab our goal is to design a 1500 seat concert hall with respect to its room acoustic qualities. We do not have to consider building acoustic aspects such as noise, sound isolation, HVAC, electroacoustics or other aspects not related to the purely acoustic performance of music in the hall. We will study a number of important design parameters such as room shape/size, absorption and diffusion, reverberation time, provision of early reflections etc.
In this lab task we have the role of consultants for the acoustic design in the early design stage of a new concert hall. We are given virtually free hands in designing this hall since the only requirement given by our assigner is that it should seat a 1500 audience and house a symphonic orchestra of 100 musicians. The hall is to be used primarily for orchestral classical music of the classical and romantic periods.
Since this task has numerous degrees of freedom it is clear that we will not be able to investigate all aspects of such a complex design task. However, we do not have to go into great detail. Furthermore we only have to consider optimizing the acoustics for the audience as stage acoustics don't not have to be considered.
Tasks
Summary
The first step is really important. Choosing the shape of the room will influence all the metrics and thus the perceived sound. Even the simplest shapes (shoebox shape, fan shape) are really not easy to deal with since a lot of effects have to be taken into consideration.
There are several different metrics that must achieve good values, knowing that they can influence each other. All those metrics depend on the shape of the room and the materials used. Changing the material means changing the absorption and the scattering coefficients and this will alter drastically the metrics therefore the sound perceived.
It is often useful to add something to the simple room in order to achieve better results (initial time gap, ..). For example a really useful and common device are the ceiling reflectors which "lower" the ceiling and scatter the sound so that the diffusivity is higher and the initial time gap is smaller for certain positions.
Designing a room for music or even for speech is something really complicated and time consuming. It requires a lot of knowledge and experience. Small details can give many differences in a good or in a bad way.