Re: Accoustic Measurments
And related to this, could it have localized conditions that vary? That may be compounded by using directional sources
I think a lot of people get false results from devices that give simple single number RT measurements. The 'old days' of using strip chart recorders and calculating the RT times involved from the resulting traces involved more work but also forced you to look at the actual trace and understand what you were using as the basis of the RT numbers. Some modern measurement platforms let you do that with greater ease and accuracy but others try to do the work for you automatically and in some cases without knowing how the calculation is made. The result is a nice simple number, that may or may not be valid.
FWIW, true RT60 numbers are a challenge to get in many venues as getting a 60dB+ S/N ratio at all frequencies can be difficult.
I bet if you asked a large number of "professionals" in this business how do you come up with an RT60 number-most would not be able to tell you. Or they would tell you "it is what the "meter" says".
How does the meter know? Based on what?
As you know- you could take the same measurement and different people would come up with different RT60 numbers-depending on where they put the cursers. In some rooms it would be pretty close-but in some other "odd" rooms, the numbers could be very different. Is there a second reverb tail? How is that accounted for? etc.
It is real easy to "throw around" numbers and such-but understanding what they really mean-and how they are derived-is beyond many peoples understanding. Yet they appear as "experts" when they talk about them.
A number of years ago we did an interesting experiment. We had at the time the worlds only portable VRAS system. So during an in house Synaudcon class we attempted to measure the reverb that it was creating.
So we choose a 3.5s room that I had programmed. When you would listen to it/clap etc-you would agree it was in that 3.5s range. We used TEF-Smaart-a program that Pat had (I don't remember the name) and the Audio Toolbox to measure it.
Guess which one was the closest? The Audio Toolbox. The others weren't within about half of the "apparent" reverb.
I figure that the Audio toolbox did it it simple way-put in a pulse and listen for the decay-the way we do it with a hand clap.
But since the reverb was not "true"-even though it sounded like a real reverberant space-the higher caliber instruments were being "thrown off" by the data they were getting.
So that would be another classic example. Does your meter/measurement agree with what you are actually hearing? If not-it may or may not be the meters fault-but could be a measurement artifact or something else. What do you believe?
I feel that to many people simply blindly take what is shown on a computer screen or a meter says and present it as fact. You need to recheck and verify to be sure.
Rant off.
