Where should we place acoustic absorption material within a room?
Sound moves horizontally within in a room. Sound reflections caused by walls can be heard most when the walls are straight and made of a hard material. We know that sound is absorbed most effectively when the absorption material is placed on ear level at the respective wall and as close to the sound source as possible. In most cases, a height of 120 cm (between 80 und 200 cm) is sufficient. At this height, the sound absorption effect is given when people in the room sit as well as stand.
In low rooms with large floor spaces, also the ceiling plays an important role. As in all circumstances, the acoustic rule applies: the closer the absorption material is to the sound source, the bigger the effect. In order to reduce sound over a long distance, we can place screens in between the different sound sources, so that sound can not only be absorbed, but also blocked
Where should sound absorption material not be placed within a room?
The rumor persists that sound absorption material should be placed at the underside of a tabletop or behind paintings or artworks, but in reality, the rule applies: “We can’t hear what we can’t see“. This means the indirect absorption of sound has only a very minor benefit, and you should save yourself going through the trouble!
Artists traditionally use canvas to paint on. Unfortunately, this material is too densely woven to be sufficiently permeable for an acoustic package that is mounted behind it, and the paint on the canvas reflects sound additionally. Also the popular canvas prints don’t have good sound absorbing qualities, either.
How do we know how much sound insulation is needed in a room? To create balanced acoustics without excess reverberations, it is usually necessary to add an absorption area of about 10% of the volume of the room.
Is it possible to demonstrate good acoustics?
To let our clients experience the possible effects of changes to the acoustics of a room, we use absorption material that can be easily mounted, and, even more importantly, quickly demounted. For this, mobile demo panels provide good results in smaller rooms up to 150 m2. They can be easily transported in a bigger car and provide, installed at ear-level, surprising results that help our clients experience the differences
But also curtains can help to absorb sound in a room: provided the material is heavy enough (e.g. velour fabric) and the curtains hang close to a wall, they can not only absorb low sound frequencies, but also eliminate echoes.
Our acoustic memory is poor:
we tend to forget very quickly, how bad the acoustics in a room used to be before changes were made. By taking away the demo-material and re-establishing the starting position, we are able to point out the differences in the quality of acoustics in a very effective way. By placing demo-panels in a room, sound frequencies in the range between 100 and 300 Hz can be improved considerably and the “humming“ in a room can be reduced.