INTRODUCTION. There are a myriad of different products on the market, these can essentially be broken down into two major categories of products:

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2 INTRODUCTION It is important to emphasize that acoustic treatment is not the same thing as soundproofing soundproofing has to do with not upsetting your neighbors (and is not something that can be addressed with off-the-shelf products), while acoustics treatment has to do with improving the sound of your control room and/or recording space. There are a myriad of different products on the market, these can essentially be broken down into two major categories of products: Diffusers and Absorbers These are aimed at dealing with four separate issues Low frequency absorption Mid/high frequency absorption Reflection Diffusion 2

3 Acoustic Issues Diffusion Typical rooms have parallel walls and floors/ceilings which lead to the creation of standing waves (even well-designed rooms will suffer from the problem to an extent). Diffusers are designed to scatter sound in all directions, both to break up standing waves, and also to create a rich and even room reverb. 3

4 Early Reflections Early reflections in the main monitoring area (i.e. the usual mixing position behind a desk with the speakers poi ti g at you are per ei ed as a s eari g hi h oth distorts the sou d a d degrades stereo imaging, as opposed to later reflections which are low enough in volume, sufficient in quantity and long enough after the original sound to be perceived as reverberation. Studio desig ers o o ly try to reate a efle tio Free )o e y a sor i g refle tio s id and high frequencies only low frequencies are not associated with this problem) at the irror poi ts when sitting in the mix position, i.e. anywhere you can see either speaker in a mirror placed on the wall/ceiling (and technically the mixer itself and the floor, although few choose to place acoustic treatment here). 4

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6 Mid / High Frequency Absorption Reflected sound from walls causes peaks and troughs in the frequency response of the room as the sound waves interact and cancel or reinforce each other at different frequencies. Absorption of sound is desirable as this prevents reflection and therefore cancellation/reinforcement. A balance must be struck with the requirement to maintain a reasonable amount of room reverb though too much mid/high frequency absorption will leave the room sounding unnaturally dead. 6

7 Low Frequency Absorption Although the requirement for low frequency absorption is based on the same principal as for mid/high absorption, it is considered separately, as firstly the methods involved are different for practical reasons and secondly it is often said that other than in the largest of well-designed spaces, you can never have too much of it. It is the biggest acoustic problem to be solved in virtually any studio, and anyone doing it well will probably spend the majority of their budget on it. 7

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9 Acoustic Treatments The simplest diffusers consist of curved panels; better ones have some sort of irregular surface, and the best feature many small chambers of various depths (the aim of the latter two being to scatter different frequencies in different directions for the most diffuse sound field). To be effective as with pretty much any acoustic treatment they must cover a good percentage of the wall/ceiling space. 9

10 Simple Absorbers So named as they deal with sound waves where they are at their highest velocity, i.e. ¼ wavelengths from the wall. As high frequencies have short wavelengths, it is not difficult to absorb them, whereas treating low frequencies in this manner takes a lot of space (this can be achieved by a combination of thicker treatment and spacing the treatment away from the wall) the low E-string of a bass guitar (41Hz) has a ¼ wavelength of over 2 meters! Absorbers are typically made of foam (not very effective unless it is very well designed) or dense mineral wool.). 10

11 PANEL TRAPS (PRESSURE ABSORBERS) Also k o as li p ass e ra es or li p ass reso ators, these deal ith sou d a es where their pressure is highest right next to the wall. The junction of two walls gives more pressure, and two walls and a ceiling/floor, yet more still, hence the customary siting of bass traps in these positions. They work by suspending absorbent material inside a box (generally dense mineral wool), and can be made more effective by loosely bonding this to a sheet of very high-density material such as mineral-impregnated rubber or sheet steel. 11

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