Reply To: Ringing Out The Room – Channel or Overall PEQ?

[Dick Rees]

My question is, what generates that sound?

Anything at all. There is no voice that I know of that can produce the 10kHz in your example as anything other than a harmonic. You also cite room resonance:

.” If the room tends to feedback at, say 10 kHz, a female vocalist is more likely to generate sound at that frequency than a baritone”

Mervakas post above gets to thhe crux of the matter. First of all, “the room” does not feed back. The sound system feeds back. The only way the room can be excited and resonate (not feed back) occurs as a standing wave directly related to room dimensions. This does not happen at wavelengths as short as 10kHz. There will be many, many other (lower) frequencies which become problematic before 10kHz becomes a problem.

In fact, you can reduce the propensity of 10kHz to be a part of the problem not just by notching the frequency itself, but by cuts at 1/2, 1/4, 1/8 the value: 5kHz, 2.5kHz, 1.25kHz and so on. Yes, these are octaves…

For those interested in understanding these phenomena, here’ a link to a calculator:

https://www.mcsquared.com/metricmodes.htm

I think you’ve thrown out a random figure in choosing your 10kHz example and linking it to room behavior only applies if the sound is directly reflected into the mic. The wavelength @ 10kHz is 1.35 inches. Such short wavelengths tend to get cancelled out to a great degree by the complex interactions of the reverberative sound field of the room.

Again, for those who wish to understand the physics involved, here’s another calculator link:

https://www.sengpielaudio.com/calculator-wavelength.htm

As I stated before, you are either mistaken in your basic understanding of the physics involved or you are having difficulty expressing yourself in clear terminology which does not render discussion moot. I refer once again to your blanket, unqualified statement of GEQ filters being “narrower” and your confusing of room resonances and feedback. We know what you SHOULD mean, but your choice of terms is so inappropriate as to confuse logical discussion. The end result is semantic quibbling rather than discussion of the topic. I endeavor to provide hard information for those interested in learning the realities of the physics of audio. That way SOMEONE reading this will understand what you seem not to.

This is getting to be pretty Socratic…if you know what I mean.