Impulse Source, Mechanical Device, Clapper

I started a thread in the subwoofer forum asking about an appropriate subwoofer for a portable room analyzer kit.

The more I searched, I am now interested in possibly using something like a clapper device to generate sound to be captured with REW for room analysis.


Here's an investigation of using such a device.

A simple impulse sound source for measurements in room acoustics​

A simple impulse sound source for measurements in room acoustics
www.academia.edu

There is a company called Larson Davis that makes a commercial one, the BAS006. But I can't find where I can buy one of those. I want to make a few prototypes, clap them and use REW to measure the response I get. Can probably do that outside so I can get reasonable results. If one of these things will generate a good response, then it might be as good or better than a sub. Certainly more portable!


Then I found this one, which looks a bit better.



In addition, I also posted an old thread about building Limp Mass Absorbers, which is very useful. I'll leave that here as well in case it helps anyone else.

Not really as that would be more appropriate for the mic. However, you could, since what' you're trying to do with the clapper is discover all the room modes and problems regardless of where they are. The clapper is an almost perfect omni source, so it's going to send sound every direction.

It's fairly common in acoustics to actually measure in the corners and other places in the room. what you're looking for are places of increased pressure, which are the same as increased loudness. Room trapping needs to be done at the places where there are maximums. Nulls are just the opposite part of the wave, actually a null can predict where a hot spot is. If there is a null at a certain frequency, you can determine where the peak will be in the room by moving 1/4 wavelength. And that's where you want to put the trap.

Of course you're going to find those at the corners and boundaries for the most part. Even if you find them mid-wall, chances are they are part of a wave that also exists at a boundary. So you find the frequencies that are increased at the boundary points and place traps that reduce the volume of that frequency at that place.

Indeed, the best instrument for exciting the room are special dodcahedron speakers like this one.


Omni sources that excite the room evenly so you can measure at all the right places.