When it comes to room acoustic treatment, you might immediately resort to standard acoustic materials such as Auralex, Fiber glass, etc. However in some parts of the world, these acoustic materials are not readily available. And if you order them from abroad, the entire cost would be enormous. So the only solution is to use readily available materials that can have similar acoustic properties of those standard materials.
The most important specifications for examining the acoustic properties of these materials are the sound absorption coefficient. It is readily available in some sound engineering manuals or acoustic engineering handbooks. It typically uses a value from 0 to 1; with 1 implying 100% absorption and 0 as no absorption. Absorption coefficient of 0.7 to 1 is considered good, while 0.3 to 0.6 as moderate and 0.3 below is poor.
This post would take a look at common materials that you can buy easily and available in most homes. So you can use this as substitute for the standard acoustic materials used in most mixing and home recording studios.
Porous concrete cement blocks – Low, Mid and High Frequency Absorbers
For those that are not familiar with this material, this is how it looks like:
Concrete porous blocks
This is commonly used as constructing materials; but its high mass; high porosity and high density properties make this material absorb sound. Try to look at the absorption coefficient data of this material:
porous cement block sound absorption
Source: sae.edu
Take note that the above absorption coefficient is for the blocks are not painted, poured with cement and not finished (so it should be rough and porous in nature). Also you can make them thick by grouping or stacking together. Since porous concrete blocks have some reasonable low frequency absorption; you can even use porous cement blocks as a bass trap. You can mount them in your room corners if you have excess blocks in your house.
Drapery Pleated 50% – A good mid to high frequency absorber
drapery pleated
Draperies are very common in homes and rooms. In fact, they have reasonable mid to high frequency absorber. Take a look at the data below:
Drapery sound absorption
Draperies have good absorptions for frequencies starting from 500Hz (or 1000Hz to be more accurate) especially if its pleated drapery. Ideally since they are placed in the windows of your room, you can use draperies to block the reflections of mid to high frequency components. You can put draperies in front and back of your nearfield monitors. If your room has windows on the sides (other than the front and back); you can as well put draperies. One big advantage of drapery is that it will help with the aesthetics of your control room.
Fabric Upholstered Seats – Acceptable all-around absorber
Well, it is important to have seats in your studio. It will be used for your clients and for yourself. If you are shopping for seats, you should use fabric upholstered seats because it can absorb a wide range of sound frequencies fairly well. This is how it looks like:
upholstered fabric seats
These types of seats do offer wide-band absorption such as follows:
absorption coefficient of upholstered seats
It is particularly very strong in absorbing mid to high frequency sound waves.
Carpet on the Floor- Mid frequency to high frequency sound absorber
You can usually find carpets sold in supermarkets and stores. And the good thing is that they are acceptable in absorbing mid to high frequencies. Take a look at the data below:
Carpet sound absorption coefficient
Source: sengpielaudio.com
The thicker the carpet, the stronger it will absorb mid to high frequencies. Carpets are not reliable in absorbing bass frequencies because they do not have the mass and density. They should not be used as bass traps.
Cotton Beds or Mattresses – Wide Band Sound Absorber
It is common to see cotton beds in the home. This type of bed uses cotton as its raw material which is a good sound absorber. The absorption coefficient of cotton is below:
cotton sound absorption coefficient
Source: BobGolds.com
To be very effective in absorbing frequencies particularly in the low end:
a.) It should be as thick as possible.
b.) It should be as dense as possible. Density is computed as mass/volume. And volume is a function of the cotton bed dimensions. If you compress the cotton bed, this will decrease its effective volume while the mass is the same; thus increasing the density which is important in blocking low frequencies. You can use 4 inches to 8inches compressed cotton bed sheets as a bass trap and it should work pretty well.
Cotton Beds
Content last updated on July 21, 2012