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|Friday, 20 November 2009 00:00|
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.
The FREQUENCY content of a sound or audio SIGNAL, often displayed as a graphic representation of amplitude against frequency. The spectrum of a sound is a primary determinant of its perceived TIMBRE.
An OSCILLATION produced in an object which resonates at the same FREQUENCY, or a HARMONIC multiple thereof, as that present in a sound wave in contact with the object.
If a sound is a complex of many TONEs of various FREQUENCY, AMPLITUDE and PHASE, repeating together in a basic CYCLE of definite frequency, the fundamental is the lowest frequency of this complex and corresponds to the unique PITCH heard in such a COMPLEX TONE.