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In Reply to: RE: RT60 measurements in small rooms posted by hellobla on December 10, 2007 at 07:10:08
In general domestic listening rooms, also the larger ones, are small in an acoustical sense meaning that the room's dimensions are small compared to the wavelengthts in question (for 20 Hz wavelength is 17.15 m or 56.3 ft).
Even if you could measure RT60 in small rooms correctly, it would not help you a lot since you don't have a diffuse but strongly directional sound field during music reproduction through loudspeakers. Further, to my knowledge the effects of reverberation in small rooms has never been thoroughly investigated. Reverberation should not be excessive but to know this you only need to walk into the room and /or clap your hands. No need to measure.
As far as ETC is concerned, why do you want to measure that? Early reflections in normally furnished rooms are above threshold of audibility
Devantier (2002), “Characterizing the amplitude response of loudspeaker systems”, Audio Engineering Society preprint 5638
Toole (2006), “Loudspeakers and rooms for sound reproduction – a scientific review”, J. of the Audio Engineering Society, p.451
so there's no need to measure. Further, such measurements don't relate to how human hearing works:
auditory filters (critical bands):
Moore et al., “Suggested formulae for calculating auditory-filter bandwidths”, The Journal of the Acoustical Society of America 1983, vol. 74, no.3, p.750
binaural decoloration:
Salomons, “Coloration and binaural decoloration of sound due to reflections”, Thesis, Delft
equal loudness contours:
Robinson, Dadson, "Threshold of Hearing and Equal-Loudness Relations for Pure Tones, and the Loudness Function", The Journal of the Acoustical Society of America 1957, vol.29, no.12, p.1284
You are probably using a single microphone, humans have a head and two ears, generating comb filters, interaural level differences, interaural time differences etc.. The whole data set is integrated and processed in the brain stem. Measurements don't take all this into account and are therefore pretty much meaningless IMO.
As for frequeny response, which one is the best? Flat, sloping upward, sloping downward? And again, you are using a single microphone so how relevant is this measurement when looking at how human hearing works?
Klaus
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