Fast receiver

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A Fast receiver is a sensor , which the particle velocity , so the air particle velocity, measures. Sometimes speed receivers are also referred to as speed receivers .

Measuring principle

The speed of sound is usually measured with hot wire sensors. These sensors do not have a membrane like a microphone , but rather very fine wires that are heated by electrical currents and more or less cooled by the rapid movement of the air. The resulting changes in resistance are evaluated. If the wires are too thick to be able to follow the individual oscillations over the course of temperature, the fast receiver only determines the rms value of the fast. Only receivers with very thin wires can also be used as a microphone, albeit not for recording studio applications.

The speed of sound is not required to explain the behavior during sound pick-up by microphones , because microphone diaphragms are moved by forces that are caused by pressures or pressure differences. Directional microphones react to pressure differences, i.e. to the pressure gradient , but not to the speed of sound. The ribbon microphone is also not, although it is often referred to as a high-speed microphone in textbooks. The ribbon was considered so light that it was previously mistakenly believed that it would follow the movement of air particles directly. But that is not the case, as a computational comparison of the speeds shows.

In contrast, the particle velocity at which is sound generation of fundamental importance, because speakers produce across the membrane movement initially an equal sound velocity immediately before the membrane. However, the physics of the sound field requires fixed relationships between the speed of sound and sound pressure . The sound medium ( air ) therefore generates pressure, so to speak, that we can perceive directly with our ears or indirectly via the microphones.

literature

  • Michael Dickreiter, Volker Dittel, Wolfgang Hoeg, Martin Wöhr (eds.), "Handbuch der Tonstudiotechnik", 8th, revised and expanded edition, 2 volumes, publisher: Walter de Gruyter, Berlin / Boston, 2014, ISBN 978-3- 11-028978-7 or e- ISBN 978-3-11-031650-6

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