How to absorb low frequency sound ( use a simple way ) ?

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danshi

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My English is poor . I want to use a simple way (method) to absorb low frequency sound .

I hire (lease) a house for 10 months . I must not to hammer nails into the wall ( I have not right ) . The house has 3 rooms .

My recording room is 3.8*3.1*2.7 meters . It's small . I stuck many sponge on the wall and ceiling , look :

http://www.audiobar.net/attachment.php?s=&postid=363786

http://www.audiobar.net/attachment.php?s=&postid=363779

http://www.audiobar.net/attachment.php?s=&postid=363784

These are the sponge I use :

http://www.audiobar.net/attachment.php?s=&postid=363777

The problem is , all high frequency sound are absorbed , but low frequency sound are not . So that there are low frequency reverb make sound cloudy .

Today I try to make some thing like this :

http://www.audiobar.net/attachment.php?s=&postid=363791

http://www.audiobar.net/attachment.php?s=&postid=363792

This is not finished yet . I hope it can absorb low frequency sound .


Any idea ?
 
Another question :

Are the thick sponge or fibre ( e.g. 100mm ) can absorb the low sound ?
 
Well -- if you can't even put a nail in the wall, then you're basically out of luck! Sticking foam on the wall will not help with low-freq absorption.

If you don't want to build your own bass traps, you can try Ethan's RealTraps - http://www.realtraps.com
 
Thank you . I have another doubt . I have read many website about low absorb . I found the the objects that used to absorb low sound are closed in a close room ( roomage ) . Is that to say : the low sound will go through wood board ?

If I place many cotton or fibre in a big wood chest ( box ) , will the low sound go through the wood board and arrive the fibre and be absorbed by the fibre ?
 
Well - the whole point about bass traps is providing a free-standing rigid mass that will absorb the low-frequency energy. Cotton fibre or foam will not do this....
 
Hey Blue, what are those mini traps made out of.....maybe Danshi (or I :D) could make our own. How about a 4 foot by 2 foot piece of 1/2" particle boardin the corners?

Also, those were listed at $159 .....each?
 
Buy some rolls/batts of fiberglass insulation, and stack 'em in the corners of your room (don't open 'em up, just stack 'em floor to ceiling). While not as effective as dedicated bass traps it's better than nothing, cheap, and you can always sell 'em later or use 'em for your own construction.
 
You could probably find some portable traps that will help a little, but I don't think you're going to see a big difference.

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Meriphew
www.meriphew.com
 
Danshi, what makes you think you need them in the first place? What are you recording? What tells you that you need them? Why fret over something you MAY not need. Kind of like this...IF, you were recording a solo flute, you would be wasting your time on a panel absorber. How low of frequency are you trying to absorb? Bass guitar? Regular guitar? Keys? From what I've read, ANYTHING that is considered a bass trap, can't even be measured for absorption below 100 hz. And NEVER has.
So IF what you are trying to absorb, is below that frequency, how does anyone know it is even being absorbed? Does that make sense? Like a tuba or sub harmonic generators....ha! See what I mean. I'm just using that as an example. You must have some relative criteria that tells you that you indeed need them. Like translation from a recording done in one room to playback in another. Does it TRANSLATE?

But in all fairness, lower and mid-low broadband absorption can be accomplished by building large panel absorbers, which are simply a sealed box with one face of a thin panel, or some fairly large box's(Slot absorbers) filled with rigid or batt type fiberglass with wood slats, slots and fabric behind the slats on the front. For details you can see these at the SAE or John Sayers site, but requires some calculations and construction savy. In fact, the walls of normal sheetrock/stud type construction act to some degree as panel absobers, and are even included in the acoustic analysis of studios by acoustitions. I'm no expert Danshi, in fact, I shouldn't even open my mouth, but I'm trying to tell you the truth AS I UNDERSTAND It.
HOWEVER, remember this. Your ROOM dimensions are what determines the frequencys that are possibly troublsome. Dimensions of the room, create MODES, which in turn produce the troublesome frequencys. These are simply the phase cancellation and addition of certain frequency sound waves per the room dim's. Someone else can explain the scientific explaination And for a rectangular room, they can be calculated, which in turn will tell you, which frequencys will possibly be a problem. There are people here who are FAR more enlightend than I in regards to acoustics and can tell you everything you need to know. I'm just trying to keep you from wasting your time and money on bullshit, if they don't chime in here with the details.
Now, there are people here who feel that ALL rooms will benefit from some bass traping, which I believe is low to mid absorption(perhaps 250hz to ?). How much do you need in square footage? I don't know. Your walls and ceiling also contribute to this absorpsion, soooo. See Ethan Winers site for info regarding purchasing OR building them yourself and maybe even Knightfly can chime in here with some real hard info . But I know you may have trouble finding certain types of absorption material (such as Owens Corning 703 rigid fiberglass), given your location. Possibly someone can send you some if you were to connect with them here. I beleive Ethan Winers company sells it raw also, but I'm not sure. And there are other materials, such as Rockwool, and proprietary foam acoustic products such as Auralux, but I would shy away from those. Anyway, I hope this helps light some of the dark corners of this subject. It is certainly an area where there are many tangibles, untruths, half truths(maybe some of mine:D ) but also there are correct ways of dealing with it.

Best thing I can suggest is to READ as much as you can here and at the afore mentioned sites before continuing with this project. Knowledge is your best defense against bullshit. I don't have the links to the other sites handy, but I KNOW they are here, on many threads in the last couple of weeks even. Just search. BTW, your english is just fine. You get your point across and that is all that matters. Hope this helps.
fitZ:)
 
I will try to make some DIY bass trip today .

RICK FITZPATRICK , I often record vocal , I just want good vocal sound .

When I sing in the room , I can hear low frequency reverb .

I will try to do something . In our country batt is very cheap , I have lot of batt to do some test . See you then .
 
Hello Danshi, read this.
It will explain the different types of absorbers and why and how they work.

http://johnlsayers.com/phpBB2/viewtopic.php?t=927

I can hear low frequency reverb .
Click to expand...
How low? That is the question. Or rather the problem defineing a solution here.
With vocals, I would think it would be a low-mid. to high mid. How small or big is your room? SMALL rooms can be a real pain to treat correctly. And that is exactly what the problem may be. Small room. For homerecordists, it usually IS the problem.

As far as vocals/reverb, still hard to say. Reverb suggest a room with live surfaces. Like EMPTY. And big. So that may be a misnomer. For a person really to prescribe a correct diagnosis and solution, they need MUCH more information regarding your room. Regardless what your ears tell you live, what does your recording tell you? Have you tried playing the recording in another room? Does it sound the same or even worse? What type of mic? Position and location of mics reletive to the ceiling and walls affect the final recording also. If your using a dynamic mic, they have what is known as "proximity effect" which boosts bass response, so to speak, the closer your mouth is to the mic, the more "bassy" it sounds. Some dynamics have a more pronounced "proximity" effect than others.

But most likely, it is the room modes. And you are the only one that can determine if what your hearing sounds bad. There is no one here that can come to your room and say.....Damn Danshi,I see you've got a square room. Thats your problem. Or....doggone, you DO have a flutter echo Dansi. Its caused by the short dimension in your room....... Soooo, from here, we are spittin in the wind....UNLESS you give the room dimensions and let someone run them on the spreadsheet that some of the guys here use to determine the modes. THEN bygeorge, we have something to work with.... make sense?

Regarding the batts....I am all for cheap. However, as usual, cheap doesn't always mean it works as good as something that may be more expensive. ..Absorption coefficents of batt type fiberglass are lower than the rigid type, and is not nearly as effective. It has to do with density of the fibersglass itself. Remember, absorption is caused by friction between the air molecules and the fiber "interstices"(I think thats how it is spelled) or intersections of the fibers. Resistance to the movement of the air molecules causes absorption. Rigid fiberglass is compressed into a rigid form which also makes it denser. Density translates into better absorption. Resistance=friction=heat..which is a simplistic explaination, but the denser it is, the better it absorbs. AND, the thicker it is, the wider the frequency range. But I'm no acoustician by any stretch of the imagination so I'll let the experts give you the real stuff :D There is also what is known as a "edge effect". Whereby the distribution of a given amount of square footage of absorbant material, will absorb LESS, than the same amount, cut into smaller pieces, and distributed around the room. Hmmm....does that make sense also? I hope so.

Something to remember when using any kind of fiberglass panel type though. By spacing the fiberglass off the wall by about an 1/2"inch to an inch(?mm) you increase the effectiveness of the fiberglass and frequency range too I believe. Exact amount off the wall or the back panel of a bass trap is not that critical I don't think either. And thickness of the actuall fiber panel also determines the frequency range of absorption too. A 3" batt will absorb somewhat less than a 1" rigid panel I believe. I don't think you are interested in absolute specs though so we won't go there.
This is only for general info. Besides, this reply is WAY too long already.

But low frequency absorption is a tough one. Because the wavelengths are VERY long. Vocals are in a low mid to upper mid range approx. Not nearly as difficult to absorb because the wave length is much shorter. If a wavelenth is within the thickness of the panel, the more it will absorb that frequency. Another simplistic view. So batts will have some absorption in the vocal range. At least for what we are talking about here. And one thing else. I ALWAYS point this out. DON"T take my word as pure fact Danshi. Ask around. Read. And here is my disclaimer. I AM NO EXPERT. These are purely my understandings of the principles and are subject to the disproval by the real experts, but I hope my ramblings are of some help. At least untill they respond.
fitZ :)
 
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