Can you make Acoustic Treatment from Household Materials?
How sound works in a room
When sound is generated from a source of some kind, whether it is a loudspeaker, a person or anything in fact, you are not just hearing the sound from directly from the source. You actually hear the sound in 2 ways.
Firstly, the listener will hear the direct sound. The direct sound is the sound that travels directly from the source to your ears. However, do not be mistaken in thinking that the direct sound is natural sounding by itself. In order to hear the direct sound only, you would have to listen in an anechoic chamber. It is a fact that any person listening to sound of any kind in an anechoic chamber would not think of any sound produced in it as being natural, as it is the reflections combined with the direct sound which make it natural sounding.
The reflections (reverberant field) is the combination of the reflections from the direct sound, reflecting off various surfaces in a room. Controlling these reflections and the frequency response of a room is what acoustic treatment is all about.
Acoustic treatment and possible DIY household creations
Porous absorbers: These are materials which are made of many tiny, individual fibers. They have high absorption coefficients (percentage of sound absorbed) at high frequencies, and much less at low frequencies. Professional porous absorbers may take the form of acoustic foam panels, which absorb a certain amount of the sound passing through it, while allowing most through. However, high frequencies and their reflections will be weakened.
A suitable household version of a porous absorber would be an ordinary carpet or rug for example. So it is therefore possible to hang rugs on the wall and record in a carpet room in order to have some cheap and effective porous absorbent effects.
Resonant absorbers: These are absorbers which resonate with a sound wave. In particular, low to mid-frequency sound waves. They can be made of perforated materials and materials with openings and slots. Due to the short wavelength of low frequencies, the resonant absorber needs to be able to move in order to absorb them, thus turning the acoustic energy into mechanical energy. Higher frequencies are absorbed with almost no movement from the absorbent material.
While there are not many things which naturally absorb low frequency energy, it is easy to make your own bass trap. However, it is not made of everyday household materials. It is basically a frame filled with fiberglass and rock wool. However, these are extremely effective if made properly.
Broadband absorbers: A broadband absorber is a type of absorber which absorbs frequencies across the entire spectrum. This means that it absorbs low, mid and high frequencies. While these can be made professionally and bought so for the best possible performance, they can also be made at home. These can be made from a combination of foam panels and bass trap material. Essentially, the broadband absorber panels will be lined with the fiberglass, rock wool, and porous absorber on top.
Diffusers: These break up reflections, therefore can be helpful in removing reflections which have escaped being absorbed. Diffusers work because of the multitude of holes and gaps within them. When sound enters these holes and gaps, they are reflected many, many times within the diffusive material, then scattering the broken up sound in all directions. Diffusers can be made or bought via diffusive panels, but there are household items which can work well. For example, a cupboard filled with clothing, though some argue it does not work well enough.
Can you make acoustic treatment from household materials? Well that depends on what you determine as household materials. There are definitely many natural porous absorbers and diffusers, low frequency absorption needs to be built in other ways.
Written by : Duran (Port Elizabeth, South Africa)
Available on Amazon : Next Acoustics Small Studio Foam Starter Kit : A great acoustic foam kit to get your small studio sounding great.
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Edited by: Rajesh Bihani ( Find me on Google+ )