This International Standard specifies a method for testing ducted fans to determine the sound power radiated into an anechoically-terminated duct on the inlet and/or outlet side of the equipment. It applies to fans which emit steady, broad-band, narrow-band and discrete-frequency sound. It applies to air temperatures between - 50 °C and + 70 °C.
The test duct diameter range is from 0,15 m to 2 m. The maxi-mum flow velocity is 30 m/s and the maximum swirl angle is 15°. An example of a method for determining the angle of swirl is given in annex F.
The one-third octave band centre frequency range is from 50 Hz to 10 000 Hz.
NOTE — The flow noise suppression of the sampling tube (see 6.2.1) may be insufficient at higher velocities and at higher angles of swirl.
DS/ISO 5136:1992 history
1992DS/ISO 5136:1992 Acoustics. Determination of sound power radiated into a duct by fans. In-duct method