This standard establishes a method of determining the octave band sound power levels of a fan. The sound power levels are determined using sound intensity measurements on a measurement surface that encloses the sound source. Guidelines are provided on suitable test environment acoustical characteristics, the measurement surface, and the number of intensity measurements. Test setups are designated generally to represent the physical orientation of fans as installed following ANSI/AMCA 210 and also used in ANSI/AMCA 300. The method is reproducible when all requirements of the method are met. This standard applies to fans of all types and sizes. It is limited to the determination of airborne sound emission for the specified setups. Minor editorial changes were made during the approval process for its designation as an American National Standard.