I’m this the comparison showed very high agreement. It was amazing how much better the SS method was for getting TL results, as compared to this traditional method.Ĭlick to expand.I believe the answer is yes. The only thing that changed when I made it louder was the area above 3khz, where TL increased a small amount once I increased the SPL to over 100dB. ![]() While I haven't shared the results, I actually got fairly accurate TL results with test tones as low as 85dB's with a sine sweep. In any case, you can see that the RTA method couldn't detect anything above 80hz accurately with tones at 90dB. Just add about 10dB's to those numbers to know what they should have been. When I then used an actual calibrator, I realized I had made a mistake in the SPL calibration, but the relative difference doesn't change. When I did that traditional method, I had used a method to calibrate the mic that I thought was right, but turned out to be quite a bit off. This method quickly ran into a noise floor problem in the receiver room. I think I accidentally captured a null in the theater.įor comparison, here is a TL measurement done using the old traditional method. I got a few odd results and averaging them gave a TL curve that didn't make sense. It didn't work so well for me, so I need to play with that when I have time. This smoothing is really needed for calculating STC, so to do that you have to keep rerunning the sweeps in different locations. You can't just move a mic around while a tone plays and the RTA records (which removes the effects of resonances and smooths the response quite a bit). Now compared to the old method, this method doesn't allow a traditional means of spatial averaging. You can see that my main losses are due to some dips between 100hz and 500hz and again above 1khz up to 2khz. There are always some issues that cost you a few STC points here and there. The wall should have been an STC of 73, but it is not shocking that I fell short of that. The others represent either the actual TL or the corrected curves of each for comparison. The flat orange line represents the STC curve I wanted to test. None the less, I believe this is right, and here are the results of that. I haven't actually done this manually before, so when I made this up, I did it according to that document, but am not 100% certain it is right. This can then be entered into a spreadsheet in accordance with ASTM E413 to calculate STC. ![]() Because this was done with a Sine Sweep measurement, I have IR's and the Green is actually the transfer function of the wall. Inside the theater, about 3 feet from the wall, and outside the theater about the same distance. The measurements were taken roughly 6-7 feet apart. ![]() The Purple is the measurements inside the theater room, Brown is the response in the room immediately adjacent to the theater. The advantage in improved S/N is significant. It is not perfect, and I learned a lot in this experiment, but the biggest thing I learned is that this is a MUCH better method for the more average DIYer like us to use in testing TL. After learning that this new approach exists and after a suggestion of how to accomplish this from Mulcahy, I believe that I have accurately tested this approach and come up with basically accurate results.
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