The paper presents an alternative approach for estimating reverberation time from measurements in real rooms when the requirements of the standard DIN EN ISO 3382-1/2 for the characteristics of the sound source, receiver, and measurement positions cannot be met. The main goal is to minimize the variance of the calculated reverberation times when using a directional source and receiver, or source-receiver relative positions with very small distances. For this purpose, the energy decay curve for individual octave bands is sampled in time. The estimation starts 2 ms after the direct sound. This is followed by several estimates of the RT over a 20 dB drop, starting 1 dB later with each iteration. The best fit mean of these values gives the estimated reverberation time. A comparison with the standard reverberation time estimation shows a variance reduction of 10% to 30% for binaural room impulse responses (BRIRs). The proposed method finds its application in situations where measurements can only be made at a few positions in the room and/or only in a few areas of the room. Furthermore, the method should be better suitable for measurements with receivers located near or at the head of a person.
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