Berliner Philharmoniker hall's reverb. Listen.

[didier.brest]

My theoretical statement said that there is a pitch change related to the time variation rate of the sound speed.

Indeed I would'nt expect this variation being fast enough for this pitch being audible. Actually I have no idea about its order of magnitude.

My statement was only a spontaneous contribution to the discussion, not the fruit of previous work or thinking.

Of course, I agree that the pitch does not depend on the sound speed itself.

[seancostello]

Originally Posted by dseetoo

TYou can observe this effect by using a tuning strobe in the hall and play a short steady note, generated by a tone generator and then watch what happens to the tuning strobe after you shut off the generator. This randomness is very necessary in a well-designed reverb system, regardless what technology it is based on.

A question: could the changes in the tuning strobe after you shut off the generator be due to amplitude fluctuations in the reverb decay?

For example, if you take a 440 Hz sine wave, and modulate the amplitude by a random function that has most of its energy under 2 Hz, what will the tuner do in this situation? Theoretically, it is the same sine wave, with a random amplitude - but signal can also be viewed as a statistical signal, centered at 440 Hz and around 4 Hz wide. Is it possible to accurate track the period of the signal in this situation?

Such amplitude modulations can be caused by pitch variations in a multitude of delayed signals, or amplitude variations in a multitude of delayed signals, or even by the spectral, time-invariant characteristics of the space (i.e. the spacing of the resonances around 440 Hz).

I don't have the answer to this question. I had thought before that the temperature variations caused speed of sound changes, but Casey's arguments against this in another thread were fairly convincing. It is certainly relevant to my work and research.

[Casey]

Originally Posted by seancostello

I had thought before that the temperature variations caused speed of sound changes, but Casey's arguments against this in another thread were fairly convincing. It is certainly relevant to my work and research.

Of course temperature does change the speed of sound. I have never argued otherwise.

I am arguing that air currents modulating the distribution of temperature within a hall over time, cannot cause audible pitch variations within the direct sound or within the ensemble of reflections (or in fact in any single reflection) within the reverb of the hall.



-Casey

[seancostello]

Originally Posted by Casey

Of course temperature does change the speed of sound. I have never argued otherwise.

I am arguing that air currents modulating the distribution of temperature within a hall over time, cannot cause audible pitch variations within the direct sound or within the ensemble of reflections (or in fact in any single reflection) within the reverb of the hall.



-Casey

My bad. I meant to say:

"I don't have the answer to this question. I had thought before that the temperature variations caused pitch changes, but Casey's arguments against this in another thread were fairly convincing. It is certainly relevant to my work and research. "

[Casey]

I think we are going to get kicked out of this thread soon anyhow.



-Casey