1984 年 40 巻 6 号 p. 414-419
It is well-known that a time constant of measuring system sometimes produces a great effect on the observed value of the reverberation time of a room, especially when the room has a very short reverberation time. In this paper, a practical method is considered for evaluating and systematically eliminating this effect. More concretely, the above measuring system such as a sound level meter and a level recorder is regarded as a power observation system and then can be approximately treated as a first-order lag element. On the other hand, the reverberation characteristic of the diffused sound room can be also treated as another first-order lag element, according to a well-known Sabine's reverberating equation. At this time, an analytical expression for the actual reverberation process of this room is derived in an explicit form containing two time constants of the room and the measuring system. Based on this viewpoint, three types of estimation algorithms are proposed for actually estimating a true reverberation time of the room from the observed data of reverberation curve affected by the time constant of measuring system. Furthermore, the legitimacy of the present theory is experimentally confirmed by applying it to the actually observed data of reverberation curve.