Acoustics. Determination of sound power radiated into a duct by fans and other air-moving devices. In-duct method
Acoustics. Determination of sound power radiated into a duct by fans and other air-moving devices. In-duct method
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1 Scope
1.1 General This International Standard specifies a method for testing ducted fans and other air-moving devices to determine the sound power radiated into an anechoically terminated duct on the inlet and/or outlet side of the equipment.
NOTE 1 For the sake of brevity, wherever the term “fan” occurs in the text, it means “fan or other air-moving device”.
The method is applicable to fans which emit steady, broad-band, narrow-band and discrete-frequency sound and to air temperatures between – 50 °C and + 70 °C. The test duct diameter range is from 0,15 m to 2 m. Test methods for small ( d < 0,15 m) and large ( d > 2 m) test ducts are described in the informative Annexes H and I, respectively. The maximum mean flow velocity at the microphone head for which the method is suitable depends on the type of microphone shield used, and is as follows:
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