This document specifies methods to measure the reverberation time in rooms. The methods are not intended to be used in consert halls and other special acoustical spaces. In these cases other, more sophisticated methods are usually required. The methods are primarily intended for use within the frequency range 100-5000 Hz. In Annex A an example of conversion of reverberation time measured in 1/3-octave bands to 1/1-octave bands is given. Annex A is not an integral part of this method.