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The rate of repetition of the CYCLEs of a PERIODIC quantity, such as a SOUND WAVE. Thus, frequency is the inverse of the PERIOD. More generally, frequency can be thought of as the rate of change of PHASE.
In the perception of ACOUSTIC SPACE, projicience refers to the sense of depth of a sound in the space.
(Greek: akouein = to hear) Commonly, the study of SOUND and its behaviour in various media and environments, including the effects of ABSORPTION, DIFFRACTION, INTERFERENCE, REFLECTION, and REFRACTION.
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.