# 30 Hz absorber



## Anthony (Oct 5, 2006)

Okay, I have a lot of details in my other thread (like pics, measurements, and what not). However, the scope is probably a bit too broad. So I will break it down into specific questions that might generate more discussion.

The biggest problem I have is a 30 Hz wide band null in the room. This corresponds with the long length of the room (19') as a half wavelength.

So what appears to be happening is that the length of the room is creating a null wave because the "bounce" off the back wall is exactly out of phase with the incident wave.

So to prevent this, I have to absorb the max velocity of the wave to prevent or limit this reflection. (max velocity, min pressure and vice versa). I think I've got this right, let me know if otherwise.

So what's the best way to do this?


----------



## bpape (Sep 14, 2006)

The null from a 19' dimension is going to be pretty low. You're better off dealing with it by not sitting in that null than trying to absorb it. Short of that, you'll likely have to build some sort of panel resonator as most standard 'soft' absorbtion isn't going to be terribly effective down that low - unless it's several feet thick. 

It's not just about where you put it but also about getting enough of the wavelength in it to make much difference.

Bryan


----------



## Anthony (Oct 5, 2006)

Hmm, I think I need to do a walk around the room with the mic (everything else being equal) and see which of these problems persist.

I didn't think I was sitting in the null (as I'm on an odd fraction of the room).

I'll take some more measurements.


----------

