Computer Music (MUSC 216)

Computer Music Terms


Sounds that are not able to bend around an obstacle, for example, those in an enclosed space such as a room are partially ABSORBED and partially REFLECTED by the barrier. Thus, when a wave of sound encounters a wall, some of the energy of the wave will be absorbed by the wall, and the remainder will be reflected as a somewhat weaker wave traveling back from the wall. The amount of ABSORPTION and the amount of REFLECTION depend upon the nature of the material on the wall. Hard surfaces, such as brick or polished stone, absorb little sound; most of the sound is reflected. Wooden panels absorb more sound, but nevertheless reflect most of the sound they receive. Curtains, drapes, and carpets absorb quite a bit of sound, however. In particular, sounds with short wavelengths higher frequencies tend to become trapped or scattered by the fibers of carpets and the folds of curtains. Thus, when a loudspeaker is placed on the floor on a deep carpet, the bass frequencies become relatively more prominent as many of the higher frequencies are absorbed by the carpet. Because of their ability to diffract around obstacles and to avoid absorption, and because of the greater amount of energy often required to produce them, lower frequencies carry well over distance. The sounds heard from a faraway stereo system are those of the bass instruments, the kick drum and bass guitar (and maybe even a tuba or bass clarinet). The frequencies of the higher instruments do not survive the journey nearly as well.

See ABSORPTION from Barry Truax's Handbook of Acoustic Ecology.

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