Understanding Room Equalization | Lexicon |
UNDERSTANDING ROOM EQUALIZATION
Sections one and two of this document explain the conditions that create the need for room equalization, how the
LOUDSPEAKER SOUND IN A ROOM
The way that sound from a speaker behaves outdoors (in open air) or in an anechoic chamber is different from the way it behaves in a room. The sound from a speaker in open air or in an anechoic chamber radiates outward in straight lines. (Actually, the theory of wave propagation is quite complex, but the “straight line” concept is valid for uniform air properties and is therefore accurate enough to be useful.) In a typical listening room, a small amount of the sound reaches the listener directly, as shown in Figure
Figure
Most of the sound in a room is reflected off walls, the floor and the ceiling, as shown in Figure
Figure
In addition, a typical listening room also contains furniture, win- dows, door openings and people. Every object and surface con- tributes a reflection.
The strength of each reflection depends on how the wavelength of the sound compares to the size of the reflecting object, and on the transmission properties of the reflector. A good general principle to remember is that if the wavelength is longer than the size of the object, the wave will pass around the object as if it wasn’t there. If the wavelength is shorter, strong reflections will occur. For exam- ple, the wavelength of 100Hz is 11 feet, so it will pass around any person standing in a room. The wavelength of 1000Hz is only 1.1