1. The preferred technique depends on the available instrumentation. If you have a TEF, you can measure the T60 almost anywhere in the room, since the TEF allows great S/N and observation of the "tail" apart from the early decay. MLS also does well, Smaart does "so so" for this. If you are using gated noise and stop watch, etc. you need to be beyond critical distance, otherwise the direct field and early reflections can interfere.

2. As far as being "in" the reverberant field, you would have to leave the room to get out of it (assuming it exists). The idea is to be outside of the direct field dominance.

3. Regarding loudspeaker directivity, I like an omni source (or close to it), even though my sound system will have directivity. I like to look at the room as just an "energy container" first. It will probably have many other uses besides being an auditorium. How long does energy "persist" in the space? T60 will be a good indicator.

4. Regarding the sound system, we can take T60 and use it to estimate the reverberant LEVEL LR, modifying LR using loudspeaker directivity, strategically placed absorption (Ma factor), etc. as we go. As Dave Prince pointed out, the emphasis should also be shifting to EDT rather than T60 as we work out the details of an appropriate loudspeaker system.

5. T60 is a useful metric, but it's only a start. Systems can work fine with long T60s as long as EDT requirements are met. In most auditoriums, reverberation will not be the major inhibitor to the clarity of music or speech, which is why EASE, CATT, ULYSSES and other programs that estimate the early-reflected field are of so much interest. This is what REALLY matters in most spaces, except your occasional cathedral.

Thanks to:
Pat Brown
SynAudCon - Synergetic Audio Concepts - "A Leader In Audio Education"

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