It has already been discussed that in home cinema setups the measure of reverberation time is really the time it takes the noise to fall by 60 dB. This is not specifically pertinent psychoacoustically, and it is also very hard to gauge in situ.
This is because of the presence of history noise in the home cinema room, either undesirable or the songs being played, which commonly results in less than 60 dB of power degeneration before the degeneration sound becomes less than the recurring noise in the atmosphere.
Even in the quieter environment of a Victorian community in the days prior to roadway traffic, Sabine needed to do dimensions, using his ears, during the night to prevent the outcomes being influenced by the level of background noise. Because we seldom hear a full reverberant decay, our ears and minds have actually adapted, fairly practically, to concentrate on what can be listened to.
Thus we are more sensitive to the impacts of the initial 20 to 30 dB of the resonant decay contour, the 60 dB echo is straight symmetrical to the earlier curves and so this need to not cause any issues when gauging in custom-made devoted home cinema installments.
Nevertheless, if the curve of a home movie theater room is of the double-slope type, then this simple relationship is broken. The web result is that, although the T60 reverberation time of the home movie theater may be a proper value, because of the much faster early degeneration to below 30 dB we perceive the cinema’s echo as being much shorter than it really is. The psychoacoustic impact of this is that the dedicated home movie theater appears ‘drier’ compared to one would certainly expect from a basic measurement of T60.
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