1.  Designing Auditoria

2. The design of various types of auditoriums (theatres, lecture halls, churches, concert halls, opera houses, and cinemas) has become a complex problem in contemporary architectural practice because, in addition to aesthetic, functional, technical, artistic and economical requirements, an auditorium often has to accommodate an unprecedentedly large audience. Furthermore, present standards often mean that the same space must be used for a number of different functions and the capacity of the room must be adjustable to momentary needs."

3. Outline of Acoustic Requirements for Good Sound
There should be adequate loudness in every part of the auditorium, especially in remote seats.
The sound energy should be uniformly distributed within the. room
Optimum reverberation characteristics should be provided in the auditorium to facilitate whatever function is required.

4. The room should be free from acoustical defects (distinct echoes, flutter echoes, picket fence echo, sound shadowing, room resonance, sound concentrations and excessive reverberation).
Background noise and vibration should be sufficiently excluded in order not to interfere in any way with the function of the enclosure.

5. Diffusion of Sound
In order to provide a high degree of sound diffusion within in an enclosure an abundant supply of surface irregularities, such as exposed structural elements, coffered ceilings, serrated enclosures, protruding boxes, sculptured surface decorations, and deep window reveals must be provided. These must also be of various sizes in order to affect all frequencies.

6. Control of Reverberation
sound-absorbing materials should be placed on those surfaces most likely to produce acoustic defects. This means that the rear wall should be treated first and then those portions of the side walls furthest from the source. There is no justification for putting absorber at the front of an auditorium or along the middle portion of the ceiling as the primary function of these areas is to reflect sound back to the .audience

8. Elimination of Defects
1. Echoes
These are probably the most serious and most common defect. They occur when sound is reflected off a boundary with sufficient magnitude and delay to be perceived as another sound, distinct from the direct sound.

9. 2. Sound concentration
Sometime referred to as 'hot-spots', these are caused by focused reflections off concave surfaces. The intensity of the sound at the focus point is unnaturally high and always occurs at the expense of other listening areas.
3. Sound shadowing
Most noticeable under a balcony, it is basically the situation where a significant portion of the reflected sound is blocked by a protrusion that itself doesn't contribute to the reflected component. In general, avoid balconies with a depth exceeding twice their height as they will cause problems for the rear-most seats beneath them.

10. 4. Distortions
These occur as a result of wildly varying absorption coefficients at different frequencies. This applies an undesirable change in the quality and tone colouration (of frequency distortions) to sound within the enclosure.