Lexicon MC-12 manual Understanding Room Equalization, Version 4 EQ User Guide

Version 4 EQ User Guide Understanding Room Equalization

feet, so it will be scattered by any person (or object bigger than 1 foot) in the room. The strength of reflections also depends on the transmission properties of the reflector. For example, depending on its size and stiffness, a wall may have its own resonant frequency. This can happen when a sound wave of sufficient amplitude hits the wall and causes it to resonate.

Parallel walls can reflect sound back and forth many times, as shown in Figure 1-3. When multiple copies of the same waveform are “added together,” they do not necessarily produce louder sound. Multiple reflections could cause an increase of more than 10dB. Yet, the level could be reduced by 10dB or more. The relative timing between the two sounds (phase difference) determines what actually happens. The end result of all these reflections is that you hear an extremely complicated sum that cannot be easily char- acterized. Fortunately our ears (actually, our brains) are able to sort through the resultant sound and interpret it all as the “room sound.” As we get accustomed to the room sound reflections, they become a critical part of our enjoyment of most music. Without the room reflections, most people would find the perceived audio quite uninteresting, even unpleasant. Logic 7 recreates these reflections.

Figure 1-3. Parallel walls reflect sound multiple times.

If you can imagine sound waves as moving objects, it is easier to think about how they interact with common objects such as humans and furniture. The wavelength of audible sound can be as long as 57 ft (20Hz) or as short as 2/3 of an inch (20kHz). A 1kHz sound wave will be about a foot long when it leaves the speaker, and it will bounce off of almost everything solid (people, walls, fur- niture) in its path. A 100Hz sound wave will be 11 feet long after leaving the speaker and, because of its length, won’t bounce off of nearly as many surfaces as the 1kHz sound wave. This concept is shown in Figure 1-4.

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