This part of ISO 13261 specifies methods for the determination of sound power ratings of air-conditioning and air-source heat pump equipment to be used outdoors.

It is applicable to the sound power rating of the outdoor sections of factory-made residential, commercial and industrial air-conditioning and air-source heat pump equipment which are electrically driven with mechanical compression and which are intended to be installed outdoors. This part of ISO 13261 includes both non-ducted equipment and equipment with ducts that terminate indoors. It includes both an octave-band sound power level rating and a single-number A-weighted overall sound power level rating.

This part of ISO 13261 does not apply to equipment which has ducted outdoor sections, or to chillers, products with variable speed compressors, or industrial process equipment.