It has already been mentioned that in home cinema installations the measure of reverberation time is definitely the time it takes the sound to fall by 60 dB. This isn’t notably related psychoacoustically, and it’s also very troublesome to measure in situ.
That is as a result of presence of background noise within the home cinema room, both undesirable or the music being performed, which frequently leads to lower than 60 dB of vitality decay earlier than the decay sound turns into lower than the residual noise within the surroundings.
Even within the quieter surroundings of a Victorian city within the days earlier than highway site visitors, Sabine needed to do measurements, utilizing his ears, at evening to keep away from the outcomes being affected by the extent of background noise. As a result of we not often hear a full reverberant decay, our ears and brains have tailored, fairly logically, to deal with what will be heard.
Thus we’re extra delicate to the consequences of the primary 20 to 30 dB of the reverberant decay curve, the 60 dB reverberation is instantly proportional to the sooner curves and so this could not trigger any issues when measuring in customized devoted home cinema installations.
Nonetheless, if the curve of a home cinema room is of the double-slope type, then this easy relationship is damaged. The web result’s that, though the T60 reverberation time of the home cinema could also be an acceptable worth, due to the quicker early decay to under 30 dB we understand the cinema’s reverberation as being shorter than it truly is. The psychoacoustic impact of that is that the devoted home cinema sounds ‘drier’ than one would anticipate from a easy measurement of T60.