An auditorium is a “place for hearing.” It’s very definition suggests that any aspect of the space that has to do with communication should be given high priority.
Prior to the invention of the sound reinforcement system, an auditorium was a space designed to allow a large number of people to be addressed by an unreinforced talker. The room geometry and acoustical treatments in an auditorium provided natural reinforcement for the acoustic source.
The ancient Greeks even built megaphones into the masks worn by actors, allowing even larger audiences to be entertained. But even with these techniques, there was really no effective way to address a very large group of people—until the invention of the sound reinforcement system.
A sound reinforcement system becomes necessary for at least four reasons:
1. Room Size—The room is too large for the natural sound from a source to be heard at distant listener seats.
2. Room Geometry—Modern auditoriums are not geometrically compatible with the human talkers. The popular 180-degree fan-shaped room is at least 60 degrees wider than what the unaided human voice can cover. As soon as a talker turns their head, some of the audience will be missed.
3. Environmental Noise—The background noise produced by occupants, traffic, and heating and air conditioning systems masks the sound source for some or all of the listeners.
4. Acoustical Treatment—The type of acoustical treatment necessary to provide natural acoustical amplification is potentially expensive and not universally suitable for all musical styles.
When a society insists on packing large numbers of people into large spaces, sound reinforcement is necessary.
An Analogy
When illuminating a room with light, appropriate fixtures are used to beam light to where it is needed. Everyone understands this. The sound system designer must do the same thing with the selection and placement of loudspeakers.
Assuming reasonably good room acoustics, some major sound problems, such as poor gain-before-feedback and poor speech intelligibility can be directly attributed to inappropriate loudspeaker selection and placement. The most common reason for this is that the sound designer was forced to abandon their first choices regarding the “what” and “where” of the loudspeakers due to aesthetic concerns.
Architecture & Sound Reinforcement
Architects often view loudspeakers as something that is foreign to the space, an “add-on” that really doesn’t belong. Architecture schools do not teach sound system design, nor should they. They emphasize the visual aspects of the venue, with great attention given to the geometry and visual flow of the space.
This is their mindset, and it is what they were hired to do. Large, prominent loudspeakers interrupt their concept of the space.
As the room is designed, the architect doesn’t know what loudspeakers will be needed or how many, making it impossible for them to integrate them into the design. And even if they could, as we will soon see that their efforts to camouflage the loudspeakers will likely impair their performance.
For the loudspeaker to do it’s job, it must occupy some of the most visually important real estate of the room. It’s no wonder that architects and sound system designers are often in conflict.
Tools Of The Trade
The sound system designer’s job is to make sure that everyone can hear what is being reinforced. They have three major variables to work with in achieving even coverage of a seating area.
