Whistle (sound generator)
The whistle is a sound generator in which a stream of air hits an edge and causes the air to vibrate in a subsequent cavity. Turbulent currents at the edge stimulate the formation of a standing sound wave in the resonance chamber. Other gases can also be used instead of air, including aerosols such as water vapor . The whistle is classified as an air leaf instrument, i.e. a flute .
terminology
The air jet is usually formed by an air duct or wind tunnel, which is also called a core gap or core gap. It meets an edge, the cutting edge , cutting edge or blown edge . The term labium is also used for this, but can also refer to the surface facing away from the resonance chamber and adjoining the cutting edge. The space between the cutting edge and the core gap is called a cut. The resonance space can form a tube or a comparable elongated body. Is the tube at the cutting edge of the opposite end open, one speaks of an open pipe , it is closed by a gedackten whistle , the sound one octave lower at equal length. If, on the other hand, the resonance space is essentially spherical or egg-shaped or otherwise a compact body, it is called a vessel flute .
The word “pipe”, from Latin pipa , in English pipe , is also used in a more general sense for woodwind instruments , which include flutes and reed instruments , for example for the group of reed pipes .
Generated sound
The frequency and timbre of the generated tone depend primarily on the size and shape of the resonance space, but also on the sharpness of the cutting edge and on the angle, thickness and strength of the air jet.
Overblown
In pipes with a tubular resonance chamber, higher tones can be generated from the overtone series of the lowest tone by overblowing , i.e. with a higher or particularly rapidly increasing blowing pressure, a sharper, narrower jet or a smaller angle between the inside of the edge and the jet . With open pipes this can be any overtone, with closed pipes only the even-numbered ones.
application
Whistles have been used as musical and signaling instruments across all cultures and ages since the Stone Age. A bone pipe from the Magdalenian period was found in the Gudenus Cave in Austria. When hunting, pipes such as B. the rabbit suit is used to imitate animal noises. When it comes to whistles that are operated with breathing air, there are signal whistles such as whistles , bosun whistles , battery whistles , high frequency whistles or flutes . In flutes, the core gap is either formed by the player's respiratory organs or is part of the pipe itself. Then one speaks of a core gap flute . Organ pipes are operated with artificially generated compressed air , and steam pipes with steam . Whistling heard most often about in the pitch of a child's voice, but often also occur in other pitches, the frequencies generated range from infrasonic range with extremely large organ pipes into the ultrasonic range at high frequency whistle .
The pitch of a bird whistle can be changed by means of a sliding piston. When pipes without an instrument it seems also to act this mechanism, but the whistle has not yet been fully explored.
Trivia
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A toy pipe as an advertising supplement for the American breakfast cereal brand Cap'n Crunch generated the frequency of 2600 Hz ( four-dashed E (e 4 )). This tone was used by the then telephone company AT&T in the 1960s to regulate line seizure. If you whistled that tone into a telephone receiver, you were able to make free phone calls. The process was optimized by John T. Draper and later known as blue boxing .
See also
literature
- Volker Straebel, Matthias Osterwold (Hrsg.): Pfeifen im Walde - An incomplete manual for the phenomenology of whistling. Maly, Cologne 1994, ISBN 3-928304-02-X .
Web links
- Acoustic flute (Engl.)