Quote:
Originally Posted by Northward  What we are trying to say is that your statement "whatever happens at low levels happens the same at high levels" is not realistic, due to many factors, some mentioned in previous posts. |
I'd sure like to see some evidence of that. What do you think would change if a test signal is played at 70 dB SPL versus 100 dB? I'm sure the frequency response and ringing would be identical, and I can't see why RT60 would be different either. So what then would be different? And more important, why?
Quote:
|
If you take an empty room with a given response. The response at point A being the sum of modal response, ER and so on. You can call the effect of the room on the signal emitted by the speakers as distortion.
|
I guess it depends on how you define distortion. All nonlinearity is distortion, but not all distortion is nonlinearity. I prefer to use "distortion" only for nonlinear behavior, but I accept that others consider phase shift and frequency response changes to be a form of distortion. But we're talking about nonlinearity here, and my initial statement was, "Room acoustics is linear, so whatever happens at low levels happens the same at high levels."
Quote:
|
Non-linearity doesn't mean at all that you're adding distortion. Just that the response at point A at 50dB isn't the same as the one at 100dB.
|
Can you show a pair of in-room response measurements at those two levels where the response is not identical? The only thing that could make two tests at 50 and 100 dB SPL seem to have a different responses is if the noise floor prevents the full extent of nulls from showing. If the noise floor is 30 dB and a null is 30 dB deep, at 50 dB SPL the null will appear only 20 dB deep because it's filled in by the room noise. At a higher SPL level the true null depth will be revealed. I mentioned earlier the importance of being above the noise floor.
--Ethan