# What's the frequency?



## MarkusBonk (Jun 5, 2010)

I have an awful peak at a certain low frequency - more about that in another thread - so I have decided to try to combat it using panel absorbers. I have built a couple - they are boxes, so I can move them around - but I have no idea how to confirm the resonant frequency and I haven't found a 'best practices for measuring membrane resonators'.

What I have tried:
I have bought an acoustic guitar pickup (is a piezo) which I attach to the membrane using powerstrips - I don't know its frequency response but I would assume that it is fairly flat (otherwise useless as a pickup).

I have put the speaker really close to the membrane near to the middle of the room - about 10cm's away and done a measurement 20-500Hz using REW.







I then took everything outside and did the same measurement in an attempt to remove the rooms influence on the measurement







The next measurement was done by simply thumping the membrane and using the rta in REW. Note the frequency scale is different to the previous two.








Which brings me to the title of the post: What is the frequency that the absorber resonates at, Kenneth?

The next question that arises is what effect would I expect to see on the rooms response?
Anyone else having fun measuring resonators?

Markus


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## Mika75 (Feb 5, 2009)

Room Dimensions ?


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## MarkusBonk (Jun 5, 2010)

Mika75 said:


> Room Dimensions ?


Well, outside is extremely large 
Inside is a bit more difficult: its L shaped the | is about 5.56m * 3.88m * 2.44m, the _ is 4.88m * 2.43m * 2.44m (i.e bounding floor dimensions are 5.56m * 4.88m)

Markus


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## MarkusBonk (Jun 5, 2010)

Am I correct in interpreting the responses such that everyone builds/buys some sort of resonator or equalizer and hopes for the best? 


> Room dimensions?


What sort of post is that? - I am talking about measuring the resonant frequency of a panel resonator and some bot chucks


> Room dimensions?


 at the thread. Probably it hasn't answered because its still trying to calculate the modes in the universe below 200Hz.

Oh, well...


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## Mika75 (Feb 5, 2009)

MarkusBonk said:


> I have an awful peak at a certain low frequency - more about that in another thread - *so I have decided to try to combat it using panel absorbers. I have built a couple* - they are boxes, so I can move them around - but I have no idea how to confirm the resonant frequency and I haven't found a 'best practices for measuring membrane resonators'.


I didn't notice this initially, but I did see the thread u started about room modes so I thought u would get a better answer about it there ..


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## MarkusBonk (Jun 5, 2010)

So I am right? If I want the usual voodoo - like chuck tons of absorbers at your room - then I am at the right place, if I want something scientific, void of all the hokus pokus I need to go somewhere else?


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## Mika75 (Feb 5, 2009)

MarkusBonk said:


> I have an awful peak at a certain low frequency


If u only sit in a small area it would be possible to equalise it out.


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## MarkusBonk (Jun 5, 2010)

Mika75 said:


> If u only sit in a small area it would be possible to equalise it out.


Lets assume I am big and sit in a large area.


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## Armand (Jul 11, 2010)

Hi.
What are the dimensions of the panel absorber you built?

Armand


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## MarkusBonk (Jun 5, 2010)

The front panel is about 0.75 * 1.2m


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## Armand (Jul 11, 2010)

MarkusBonk said:


> The front panel is about 0.75 * 1.2m


And what is the depth?
And how much filler did you use? 
I am interested in comparing your measured results with the theoretical data. As I am planing to build the same thing myself.
_Posted via Mobile Device_


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