It is not necessary to acoustically treat the entire room to achieve good results. Strategic treatment of specific locations can realize considerable benefits. Remember that when sound waves reflect from a flat surface, the angle of reflection is equal to the angle of incidence, just as a mirror reflects light waves. Therefore, the most important location for sound absorbing material is the point where the sound waves reflect to the listener (see Figure 8.2).
Figure 8.1 - The reflected sound must travel further than the direct sound, and therefore reaches the listener at
a later time.
Figure 8.2 - The sound is reflected at the same angle that it struck the surface; i.e., Angle X = Angle Y. Since light waves obey this same rule, a mirror can be used to find the point that can be acoustically damped to avoid early reflections.
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