acoustic sound absorption panels

i reside in west bengal and im planning to have all the walls and the ceiling covered with some acoustic absoption panel. please advise

use simple bed foams that you can buy from that shop where you purchase all you bed mattress,cusions ,curtains,pillows etc etc

get foams in different size

1 inch for high frequency absorption

2 inch for mid frequency absorption

and 4 to 8 inch for bass traps
for your back wall use diffusers made from thick materials that don't absorb any sound like thermocoal,wood

If you want to build a simple working sound trap, build a thick mattress of the lowest density loose Rockwool. Rockwool is manufactured by Minwool Rock Fibers Ltd based in Hyderabad. There are also many other companies too, that manufacture rockwool.

The depth of the mattress should be slightly more than the size of the quarter wavelength of the lowest frequency you want to absorb. For example, if you want to absorb all the frequencies above 80Hz, the full wavelength of 80Hz is about 4.3m so the quarter wavelength is about 1.07m. A rockwool mattress that about 1.1m depth will absorb all frequencies above 80Hz.

Such traps are best located across the back wall of the room, that is the wall behind you when you are looking at your speakers.

Hi,
I did ask a dealer what he used in his demo room (they are rather well padded
He suggested buying glasswool rolls (for about 3.5K INR per roll), plus basic wooden frame and cloth of own choice (his suggestion was to use anything that doesnt absorb /retain moisture). With these, you should be able to build you panels.
I think the previous poster has referred to rockwool (which is probably the same thing) - then this would be the right way to go. Thickness is about 1 inch or more.
else you can use egg crates (ive seen it used when i was a broke student .. heheee)
cheers!

Recently I have used 'CERA WOOL' for heat insulation, while inspecting the material I thought it could be used for sound absorption too, it is similar to glass wool but does not have itching property and is available in sheet form of size 1" / 2" thick, 24" width and 24' (foot) length.
Can we use gypsum board on the wall to absorb sound?

Rockwool is quite similar to Glasswool. However exposure to fine Glasswool fibers may be bad for health whilst Rockwool is considered safer

The depth of the mattress should be slightly more than the size of the quarter wavelength of the lowest frequency you want to absorb. For example, if you want to absorb all the frequencies above 80Hz, the full wavelength of 80Hz is about 4.3m so the quarter wavelength is about 1.07m. A rockwool mattress that about 1.1m depth will absorb all frequencies above 80Hz.

Hi, Sorry i didnt understand "A rockwool mattress that about 1.1m depth will absorb all frequencies above 80Hz." did you mean 1.1 meter depth or 1.1cm or 1.1inch depth.

1 meter thick foam!!! where will I get it? I think there won't be any space left in my room for furniture if I sacrifice 2 meters of space in each dimension!

Perhaps this ideal room attached drawing will explain things more clearly. To calculate the quarter wavelength, take the speed of sound which is 343 meters per second and divide it by the frequency, which gives you the full wavelength. Then divide it by four to get the quarter wavelength

343 ÷ 100 = 3.43 ÷ 4 = 0.86 meter
343 ÷ 90 = 3.81 ÷ 4 = 0.95 meter
343 ÷ 80 = 4.29 ÷ 4 = 1.07 meter
343 ÷ 70 = 4.90 ÷ 4 = 1.23 meter
343 ÷ 60 = 5.72 ÷ 4 = 1.43 meter

So if you want to trap all the frequencies from 100Hz & above, the trap depth has to be more than 0.86 meter. If you want to trap all the frequencies above 60Hz, the trap depth has to be more than 1.43 meter ..... and so on. Its advisable to have a rear wall trap of 1.1 meter so that all the directional frequencies above 80Hz are totally kept under control.

Attached is a sketch of an ideal Reflection Free Zone (RFZ) also known as Controlled Image Design (CID) room. Notice how all the reflections are diverted into the rear bass trap and absorbed there. It is impractical to try and absorb the side wall reflections with massive traps. Whilst it is easy to put lots of absorption on the rear wall and perhaps even on the ceiling. This way the natural ambiance of the room is maintained keeping the side walls hard and bare. All the hard walls are non parallel, eliminating standing waves.

So building an ideal listening room is not that difficult if you have the space.

Attached Files

RFZ or CID.pdf (17.4 KB, 39 views)

Though this sounds idealistic, building a full wall bass trap that is nearly 4 feet thick is practically impossible. It may make more sense to build a full wall book case and line it with book for dispersion. Even hanging a thick curtain some 2 or 3 feet from the wall and using it only during music or movie session makes more sense. Rest of the time the curtains can be drawn back to make the place look better.

It will be easier and (maybe less expensive) to build small absorption boards and hang then on the parallel walls, as well as build floor to ceiling bass traps on two corners.

Cheers