This standard applies to steady, broad-band, narrow band. and/or discrete frequency sound at air temperatures between −50°C and 70°C. The test duct diameter range is from 150 mm to 2 m. The maximum flow velocity in the duct is 30 m/s and the maximum swirl angle is 15°. The frequency range is from 50 Hz to 10.000 Hz.

This standard applies to sound sources connected to a duct. Examples of equipment covered by this standard are:

(a) centrifugal fans,

(b) axial-flow fans,

(c) mixed-flow fans,

(d) air-handling units,

(e) unitary equipment,

(f) furnaces,

(g) dampers, and

(h) throttling devices.

This standard does not apply to non-ducted equipment.