JBL Control 23 Owner's Manual page 8

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•Incident/Reflected/Absorbed • JBL
Control® Contractor series speakers
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are designed as fixed installation loudspeaker systems for use in a variety of
environments. Performance may nevertheless vary from room to room
because of differences in the acoustical setting. Since an enclosed room
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presents acoustical boundaries (walls, floors & ceilings), sound indoors
exhibits quite complex behavior. Each time a sound wave strikes a boundary,
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part of the wave's energy is reflected and part is absorbed (see diag. 1 ).
Reflection & absorption are dependent on the frequency of the sound wave
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and the angle at which it strikes the boundary.
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• Absorption - When designing your system, note that
. people and furniture absorb sound, while glass and tile
reflect sound. The percentage of energy that a boundary
absorbs is often expressed by an absorption coefficient of
the boundary material, where an absorption coefficient of
1 =complete absorption and O=perfect reflective surface (see
diag. 2).
ONE LOUD SPEAKER MULnPLE QUIET SPEAKERS
• Reverberation - Reverberation is the reflected sound
waves continuing to bounce between the boundaries, losing
energy with each reflection. When sound strikes the reflec-
tive boundaries of a room, after a time the room is filled with
random reflected sound waves. Music and speech become
unintelligible (see diag. 3A). To minimize reverberation in a
highly reverberant room, it is advisable to install more
speakers, and play them at lower levels (see diag. 38).
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