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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.
In music, an adjective referring to HARMONY and its principles. In ACOUSTICS, when a vibrating object, such as a string, is set in motion, it vibrates both as a whole, with a FREQUENCY called the FUNDAMENTAL, and, with lesser intensity, in sections as well. If these smaller lengths are integer fractions (1/2, 1/3, 1/4, ...) of the total length of the string, their frequencies of OSCILLATION are called harmonics, and are integer multiples of the fundamental.
When a system with a natural vibrating FREQUENCY is stimulated by an outside force of the same frequency, the system can be set in a motion called VIBRATION. As the frequency of the stimulus closely approaches that of the system, OSCILLATION occurs, which reaches a maximum AMPLITUDE at the natural resonant frequency.
(French: concrete music) A development introduced in Paris in 1948 by Pierre Schaeffer at the studio of the French Radio (O.R.T.F.). Its aim was to replace traditional musical material with recorded (i.e. concrete) sounds which were then manipulated by FILTERing, tape reversal, TAPE LOOPs, speed changes, tape SPLICEs, or other electronic means. The source of all sounds, however, was environmental. The experimental side of this study developed the concept of l'objet sonore.