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The use of reflected SOUND WAVEs for obtaining environmental information. Certain animals, such as the bat and the porpoise, emit pulses of extremely high frequency sound (up to 50 kHz for bats, and up to 170 kHz for porpoises and whales) in narrow, intense streams. The REFLECTION, or ECHO, of these sounds supplies information regarding the nature and location of objects in the environment. When an emission of varying frequency is used, such as with bats, the echoes, travelling varying distances to the ear, are heard as different frequencies in each ear, thus supplying directional information.
Also called flanging or flangeing. An effect created by adding together two identical SIGNALs separated by a very short time delay (less than 25 ms, but strongest below 10 ms). These short delays are within the audio WAVELENGTH range, and the combination of the two signals affects the frequency SPECTRUM of the composite sound.
A pre-recorded or simulated sound produced for a radio, television, film or theatrical program in order to suggest an actual sonic environment. The design of such sounds (often abbreviated as SFX), particularly when a complex acoustic environment is to be simulated, involves a thorough understanding of the structure of such a SOUNDSCAPE; that is, what sounds are representative and most significant, as well as which are necessary to create a given AMBIENCE and sense of ACOUSTIC SPACE.
Sound at frequencies above the audible range, namely above 20 kHz, audible only to various non-human species. Because of its very short WAVELENGTH in the megahertz range, ultrasound is used as a safe alternative to X-ray photography in medical diagnosis. Ultrasound scanning is sometimes called sonography.