Accoustic Foam.... I think I'm crazy....

What an absolutely top thread this is, even if I do not understand half of it. Hooray for Mosfet and Tenson and others for their technical know-how, for I am in the relative dark here here,yet mega-interested in this subject.

To explain, here's MY situation. I live in a flat with brick(wall) and concete) floor bound. Concrete loors are a surprising conductor of low fq sound to below. I have noone above. My main concern is neighbour transfer, but not surprisiongly sound quality is also of importance.

I already use Auralex Gramma foam/mdf platform platforms for my floorstaning speakers. I (think ) the make a big differncnce in transmition in the first place. The speakers I am about to buy are very much stronger than b4 and if I go for thednaudios, they go as low as aboy 28/30. I am mega intereted in whether the bass traps that are available effectively damp the low frequencies they are rated for with respect to neighbours as well as in room. In other words, if I DO buy low fq capable speakers, if I buy effective bass traps, will I , I mean I , appreciate it, rater than than my neigbour be bugged by it ? This is a problem faced by a good half of our posters here !

 

Sorry grammmital nonsenseeeee, as I be pished and somewhat incabable of rendering de gramma properly! But you knows what I means.


Zappa fans, will recognise de Thing Fish !

 

And by the way I am not Chinese ( having just reviewed my last two wine tinged posts ! )

 

Good bass traps will make a bit of difference to how much bass is getting to your neighbour as they soak up some of what is in the room, but I don't think they will stop it a great deal. They will mean however, that you can place the speakers closer to the walls because the walls will be reflecting less energy. ..I'm sure someone asked about that.

Sound proofing is about isolation as much as absorption. To stop the sound getting to the neighbours you want to isolate your room. A common method is to build a room within a room but you might not want to go to that length.

To make a current wall more sound-isolating you can build a second skin with sheets of plasterboard and space them away from the current wall by about 4 inches. Behind this the gap should be filled with fibreglass sheets, but make sure neither walls touch this because you don’t want vibration transfer so there needs to be a small gap on either side. After that you need to seal all gaps with bathroom sealant or similar so that the new wall is air-tight, this means right along the ceiling, floor, walls and gaps between the plasterboard sheets. At the end you should have a pretty good wall! Please note this really only works on a concrete floor because on a wooden one the sound will transfer through the floor by vibration – that’s why we normally build an entire room within a room suspended on rubber mountings rather than just a single wall.

 

Hi Tenson,

All the best ideas come in two's - I've sent you a PM.

Alex

 

Another method of soundproofing a room is to use a constrained layaer damping material between 2 layers of plasterboard, can be applied direct to existing stud wall or can be used as part of a new construction.

 

Hasn't that type of wall got a name.. I was trying to think of it last night, its someone’s name (beginning with D?) and then double wall I think. Anyway I was thinking of the same thing only using the existing wall instead of the second layer of plasterboard.

 

Cloth Ears

There's a definite distinction to be made between sound absorption and sound proofing. Absorption is more concerned with correcting or changing the room acoustic so, for instance, the low frequencies sound less overblown or to make the mid to high frequencies more intelligible. Proofing is concerned with preventing the transmission of sound from one space to another. Both use different techniques and different materials although a combination of the two can be employed.

To soundproof a room you need to look at mass loaded sheet installed as a sound barrier between partition walls and floors. Better still is to go for some fairly serious structural re-work – as suggested above - using fiberglass panels with a bonded mass loaded backing. A lot of work!

In-room absorption (a pair of corner bass traps for instance) is much less effective at preventing transmission of low frequency sound compared to sound proofing techniques; it will help tho' but you do need to think BIG at low frequencies for porous type absorption. Have a look here

Get yourself a copy of the latest Studio Spares catalogue and also have a look at this website http://www.customaudiodesigns.co.uk/


Alex / Tenson, if you can come up with a design that passes the “don't think you're having that in here†female test then you'll be on to a winner! Looks good!

 

God don't mention the StudioSpares catalogue, I get three every time instead of one!! I can't stop them!

 

cant think of the wall name, im thinking of using a material like Greenglue in the wall construction(www.audioalloy.com) rather than other methods like MLV
lots of wall constructions here: http://www.asc-soundproof.com/wd-desw.htm

 

Thanks for those replies.

I already know the customaudiodesigns website from a year ago I did some improvements in my flat but I decided not to do all that contsruction work, e.g. building a floating floor with various products, building a new wall, etc. Its all very very expensive when you do the costings.

I first saw the Auralex Gramma platforms on that site and I ended up buying a pair from an American supplier, for use under my floorstanders. I believe they are pretty effective in stopping vibration going into the floor. Believe it or not that concrete floor does vibrate ( its not thick ). I think it let me get away with floorstanders.

My main interest in this thread is really with in room influences on misbehaving sound. e.g. boomy bass, reflections off wall behind sofa, etc etc. I'm about to buy serious speakers so I want to aid room acoustics now if I can.

Is it just trial and error with traps and pads if you don't have access to an analyst or can't afford one?

 

There are some guidelines you can follow.

Put bass traps in corners because thats where bass 'gathers'. - if you have foam bass traps you can increase their effectiveness by placing them off the wall a bit.

Bass is omni-directional so it is worth treating the area behind the speakers, but mid and high frequency is not, so you will get more effect from thin absorptive and/or reflective panels if they are placed 'in the line of sight' of the speakers.

Put absorption or diffusion at first reflection points. – Use a mirror and a helpful hand to find them.

Diffusion works well on the ceiling and maybe the back wall if you are a reasonable distance from it.

If you use membrane bass traps you will probably also want some broadband absorption in or across corners or anywhere that sounds 'coloured' that is 'in sight' of the speakers. Foam bass traps are basically broadband absorption so if you use these in all corners you probably won't need extra broadband treatment as well.

Remember there are not only corners where the walls meet but also where the floor and ceiling meet the walls.