brett wrote on Thu, 18 December 2008 20:08 |
I have a ceiling mode of 70hz and 140hz. Will the 1/4 plywood work. I am not sure what freq are considered "deep bass " vs "mid bass"? |
Ethan Winer wrote on Sun, 11 January 2009 13:08 |
You can't put wood panel traps in front of each other ... [snip] |
Thomas Jouanjean wrote on Tue, 13 January 2009 21:43 |
What is important with membranes in studios is that the energy transmitted to that membrane is lost in heat and not re-emitted. |
Bruno Gouveia wrote on Mon, 02 February 2009 07:55 |
This is the hard part, the damping of the membrane! How can one the predict objectively the behavior of a membrane? |
Bruno Gouveia wrote on Mon, 02 February 2009 07:55 |
Perhaps it'safer to put it behind something and that something will prevent the coupling of the natural vibration of the membrane with air, and that's what we want! |
Thomas Jouanjean wrote on Mon, 02 February 2009 15:46 |
If you have proper data, you can estimate the behaviour pretty accurately . Experience also helps refining techniques. Yes, membranes should be "in-between" other materials (undampened), the type depending on the design objectives and freq one is looking for. Those complex sandwiches give solid results. But they are massive! |
Bruno Gouveia wrote on Mon, 02 February 2009 10:55 |
What kind of software / method do you use to predict the behaviour of a panel? |
Bruno Gouveia wrote on Mon, 02 February 2009 10:55 |
If we could really achieve accurate estimates of the behavior of a membrane maybe it would be possible to have even more efficient results! For instance, using a metal membrane which exposed to sound reverbs like hell, if we get a way to stop the sound that comes in from going out, maybe we could achieve impressive absorption with a relatively smaller size in comparison from what is commonly used. |
Thomas Jouanjean wrote on Mon, 02 February 2009 18:32 |
Manufacturer's data (when available) and discussion with specialists -> real-life / empirical testing -> Data to software (MATLAB etc) -> estimation within the desired confidence interval. Then real-life test in situ. With time you build-up a database, that you refine constantly. To design studios, I work both in B&K ODEON and AUTOCAD (to draw plans) |
Bruno Gouveia wrote on Mon, 02 February 2009 18:42 |
Very interesting! The absorption as described makes sense and it will lower the sound levels in a room, but for music rooms will it work? http://www.ntnu.no/gemini/2006-01e/deamp.htm I've followed this article in the press section of their site. The metal absorbers, thin as they are likely to sing like a bird, and we already know re-radiations can be very dangerous to music... |
Bruno Gouveia wrote on Mon, 02 February 2009 18:51 |
I've a friend who is a mechanical engineer and his job is to design boxes to hold electronic PCB that must endure extreme and severe conditions like a rocket launch and space. He uses a software called NASTRAN http://www.mscsoftware.com/products/msc_nastran.cfm?Q=131&am p;am p;Z=396&Y=422 that seems really powerful in predicting vibration modes. |
Thomas Jouanjean wrote on Tue, 03 February 2009 08:04 |
NASTRAN seems very interesting, thanks for the tip. Does it work well for smaller surfaces? I noticed that the smaller the surface, the less accurate the estimation. Did you use it yourself? |
Thomas Jouanjean wrote on Tue, 03 February 2009 07:59 |
Moreover, they allow to keep the light in - which will make the client happy. If you want, I'll share the results of our first shot at them? |
andrebrito wrote on Thu, 05 February 2009 11:10 |
Bruno, One thing is to predict the behavior of a box, another to predict the behavior of a box within a room and a sound field all together. |
Bruno Gouveia wrote on Thu, 05 February 2009 05:26 |
For instance, in many rooms I still can't tell for sure what's causing the reverberation, is it just reflections or is it reactive energy? |
andrebrito wrote on Thu, 05 February 2009 06:18 |
Anyway I find it too much work to do for a studio recording project and like Thomas I might use computacional acoustics if the client can afford it (usually they cannot lol). |
Thomas Jouanjean wrote on Thu, 05 February 2009 20:15 |
Ah, the joys of re-emission... Both The hardest part is when materials store energy and then re-emit periodically at their resonance frequency. |
Bruno Gouveia wrote on Thu, 05 February 2009 14:31 |
My explanation is that as bass frequencies are more difficult to propagate through air they get trapped by the air itself and so the panels eventually absorb the energy as they vibrate, whereas in the small room we get to ear the vibration. |
Thomas Jouanjean wrote on Thu, 05 February 2009 20:46 |
I'm not sure I understand you there... LF propagate very good in air, and carry a lot more energy. What you describe here is normal absorption by membrane like-panels, which take LFs 'out' of the room. Re-emission from those should fill the room with particular frequencies and up to a point (and not necessarily the ones emitted in the first place). Although I agree distance plays a role in how much you hear it (normal behaviour though). |
franman wrote on Sun, 08 February 2009 20:30 |
Hey Thomas and Bruno... I don't consider myself an expert by any means in large room acoustics, but I know the physics is basically the same. There are typically different goals. I'm a little confused too: We use Membrane Traps, Helmholtz Resonators and other Broadband LF trapping to INCREASE the amount of percieved bass in a (small) room like a control room. In other words, the more we trap, the better and tighter and more detailed the Bass sounds. It is a popular misconception in control room treatment, that bass traps will "remove" bass from the room... BUT, this seems to be what both are you are implying unless I'm not understanding correctly>>> that too many loose panels acting as membranes will take bass response away from the room.... Am I getting this right?? sorry for my confusion.... Maybe it's totally different in large performance spaces, but I know how larger recording rooms behave and we still strive to add sufficient LF trapping in these rooms to ensure the bass is tight and the decay is comparable to the rest of the spectrum... as you know it's easy to absorb too much High and Mid frequency and end up with a boomy sounding room. Thoughts>???? |
franman wrote on Sun, 08 February 2009 14:30 |
We use Membrane Traps, Helmholtz Resonators and other Broadband LF trapping to INCREASE the amount of percieved bass in a (small) room like a control room. In other words, the more we trap, the better and tighter and more detailed the Bass sounds. It is a popular misconception in control room treatment, that bass traps will "remove" bass from the room... |
franman wrote on Sun, 08 February 2009 14:30 |
BUT, this seems to be what both are you are implying unless I'm not understanding correctly>>> that too many loose panels acting as membranes will take bass response away from the room.... Am I getting this right?? sorry for my confusion.... Maybe it's totally different in large performance spaces, but I know how larger recording rooms behave and we still strive to add sufficient LF trapping in these rooms to ensure the bass is tight and the decay is comparable to the rest of the spectrum... as you know it's easy to absorb too much High and Mid frequency and end up with a boomy sounding room. Thoughts>???? |
Thomas Jouanjean wrote on Mon, 09 February 2009 08:10 |
Chances are these re-emit in the LMF band too, therefore increasing perceived energy with regards to bass, increasing the imbalance. (Those modern rooms I have visited have little to no MF treatment as well. Treating HF is no use, air does that job pretty well.) |