DIN EN ISO 5136:2009-11

This standards specifies a method for the measurement of the sound power radiated into a duct by fans and other aerodynamic sound sources (dampers, throttles, boxes). The standard is mainly intended for measurements of air-moving devices, for the measurement of flow noise from air-handling (passive) units ISO7235 is recommended. The source under test must emit steady noise. The measurements are carried out in ducts with circular cross sections between 0,15 m and 2 m. Normative annexes describe measurements in ducts with diameters between 0,07 m and 7 m. The air temperature during the measurements must lie between -50 °C und +70 °C, at flow velocities of up to 40 m/s (informative up to 60 m/s) at a maximum permissible swirl angle of 15°. Measurements are carried out in one-third-octave bands between 50 Hz and 10000 Hz (informative 20000 Hz).