ASHRAE research project 624-RP investigated measurement procedures for extending the frequency range of sound power tests in reverberation rooms down to the 63-Hz and 31-Hz octave bands for broad-band and discrete frequency sound sources. There were four main areas of investigations - (1) a literature review, (2) a detailed study of the sound field in a model reverberation room, (3) a study of the reproducibility of the substitution method for both one-third-octave and single-frequency measurements in a number of reverberation rooms with different sizes and configurations, and (4) calibration of the sound sources used in the investigation by the intensity scan method. The project results suggest that the substitution method is the most suitable method for measuring sound power at low frequencies in reverberation rooms. The reproducibility and accuracy of the method, while larger than the values at frequencies of 100 Hz and above, appear to be acceptable.

KEYWORDS: Laboratory testing, measuring, sound, intensity, reverberation, rooms, calibrating, accuracy, research.