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Much shorter than that, actually. Only the subjects in the amp test could have developed listener fatigue.
I'm a little confused at this point I'll give you the source and leave it at that:
III. The Magic of 85 with Film Mixes (p. 4) - again, same article
http://www.aes.org/technical/documentDownloads.cfm?docID=65
I'm not trying to be argumentative. I'm confused too, by one quote of the AES meeting having one number and Katz quoting every word exactly except using 83 instead of 85. And Katz is who arranged for the presentation to occur. And the AES version is Katz as well. I think the answer for Katz is in the appendix on the page I already linked. I quote it in blue below.
Which still is odd and confusing.
This page below is very clear regarding THX levels. As Tom Holman is the TH in THX, it looks like Katz made his own 3 db adjustment. And quoted while making that adjustment in his web posting.
http://www.acousticfrontiers.com/2013314thx-reference-level/
So it appears that 85 db SPL pink noise is the proper Reference level for large theaters. Maybe the 82 I've been using for years was a lucky happenstance for domestic rooms.
https://www.digido.com/portfolio-item/level-practices-part-2/
All quoted monitor SPL calibration figures in this paper are referenced to -20 dB FS. The “theatre standard”, Proposed SMPTE Recommended Practice: Relative and Absolute Sound Pressure Levels for Motion-Picture Multichannel Sound Systems, SMPTE Document RP 200, defines the calibration method in detail. In the 1970’s the value was quoted as “85 at 0 VU” but as the measurement methods became more sophisticated, this value proved to be in error. It has now become “85 at -18 dB FS” with 0 VU remaining at -20 dBFS (sine wave). The history of this metamorphosis is interesting. A VU meter was originally used to do the calibration, and with the advent of digital audio, the VU meter was calibrated with a sine wave to -20 dB FS. However, it was forgotten that a VU meter does not average by the RMS method, which results in an error between the RMS electrical value of the pink noise and the sine wave level. While 1 dB is the theoretical difference, the author has seen as much as a 2 dB discrepancy between certain VU meters and the true RMS pink noise level.
The other problem is the measurement bandwidth, since a widerange voltmeter will show attenuation of the source pink noise signal on a long distance analog cable due to capacitive losses. The solution is to define a specific measurement bandwidth (20 kHz). By the time all these errors were tracked down, it was discovered that the historical calibration was in error by 2dB. Using pink noise at an RMS level of -20 dBFS RMS must correctly result in an SPL level of only 83 dB. In order to retain the magic “85” number, the SMPTE raised the specified level of the calibrating pink noise to -18dB FS RMS, but the result is the identical monitor gain. One channel is measured at a time, the SPL meter set to C weighting, slow. The K-System is consistent with RP 200 only at K-20. I feel it will be simpler in the long run to calibrate to 83 dB SPL at the K-System meter’s 0 dB rather than confuse future users with a non-standard +2 dB calibration point.
It is critical that the thousands of studios with legacy systems that incorporate VU meters should adjust the electrical relationship of the VU meter and digital level via a sine wave test tone, then ignore the VU meter and align the SPL with an RMS-calibrated digital pink noise source.
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