Noise and reverberation (echo) are two things that audio engineers want to control. When I thought about this article I wanted to consider these two separate effects in two different situations - the closed broadcast studio where you sit and speak in a silent room and the open-concept studio where an audience, or video as well as audio, affects the sound quality. Noise - that sound which is loud, harsh or unwanted - and reverberation - the reflected noises that echo or bounce back - can be controlled, even to the extent that they can enhance the recorded or broadcast signals.
Let's first consider the enclosed booth, usually used for a broadcast room, music practice room, translation booth, etc. The purpose of these rooms is to give a proper acoustic environment the person (s) inside by blocking any unwanted noise from the surrounding area, and at the same time allowing the person (s) to have good speech intelligibility.
These enclosed booths can be built in two different ways. The traditional approach is to build separate 2 x 4 stud walls, filling the cavities with insulation - leaving an air space between the walls - and covering the outside and inside with a heavy layer of high mass such as gypsum board. The joints at the floor and ceiling are well sealed, and usually the structure is placed on rubber anti-vibration supports to stop any structural borne noise. Special consideration has to be taken with the incoming and outgoing air, to make sure that any noise either from the outside or from the mechanical air-handling system does not interfere with any broadcast signals.A room built in this fashion will be highly reverberant inside. The walls and ceiling will need to be wholly or partially covered with a noise absorbing material such as fiberglass panels covered with an open-weave material to reduce the reverberation (echo).The modern approach to broadcast studios is to build a modular-panel room using pre-built panels. These panels are designed to block out noise by having a solid outside skin and to absorb any reverberation on the inside by having an absorbing inside skin (usually perforated metal). Utilities such as lighting, cable access ports, silenced air ventilation, vibration-isolated floors, acoustic windows, acoustic doors, and designer interiors can be built at the factory and shipped for installation to the building site. This approach saves time, especially during installation - a cost saving measure that has to be considered by the purchaser.
Acoustic treatment to larger areas, where individual studios are not practical, takes a different approach. These areas may be functional, but then you introduce people and their activities, the resulting noise is contained by the walls and the resulting condition is called reverberant noise. All construction materials have some absorptive qualities; many such as concrete, glass and steel are low on the absorptive scale. Noise energy within a confined space is easily reflective off these materials, producing an echo, or reverberation, effect.Acoustic treatment to larger areas, where individual studios are not practical, takes a different approach. These areas may be functional, but then you introduce people and their activities, the resulting noise is contained by the walls and the resulting condition is called reverberant noise.All construction materials have some absorptive qualities; many such as concrete, glass and steel are low on the absorptive scale. Noise energy within a confined space is easily reflective off these materials, producing an echo, or reverberation, effect.
The traditional methods used to reduce the echo in larger spaces was to add non-reflective materials such as cork, carpet and drapes, (a living room with wall-to-wall carpet and drapes is acoustically "softer" than a bare room). Although these were good materials, the coefficient of absorption was not consistent and whole surfaces were covered to overcome this defect and reduce the reverberation effect. Today special acoustic panels with known acoustic values are used. There are formulae to calculate the absorption of the existing construction materials and the volume of the rooms to determine, with accuracy, the existing reverberation time. This will allow the acoustical consultant to determine the amount of absorptive panel to add to any large open space to achieve a predetermined reverberation time and noise reduction.The resulting new, lower reverberation times can be established before the materials are applied to the room. This "what if" calculation is helpful to the architect and the user to establish the room acoustics before construction or retrofit. Typical types of reverberation-reducing panels are fibrous glass covered with fabric and perforated metal panels with acoustic material behind the pre-painted metal to absorb the noise energy. Both types of panels can be made to be architecturally and functionally pleasing.
In conclusion, you can isolate people in traditionally constructed studios or use the up-to-date modular steel panel approach for broadcast, recording, and newsrooms. The cost savings of modular panels are advantageous, and sometimes they are more practical. In larger volume spaces you cant treat all of the surface areas to make sure you reduce the reverberation enough, or use a pre-made acoustical panel system available from a number of sources and usingdifferent absorbing materials.
The advantage of the pre-designed panels is that you are working from a predetermined acoustical base, and can plan in advance the type of acoustic values you wish to achieve.
