Acoustic design is one of those often ignored aspects or architecture – and it shouldn’t be. As Master of Sound Julian Treasure says:
“Sound must be carefully considered in the design process, whether for a building or an environment…There is no time to lose in getting this message across to architects, planners, government, and those commissioning buildings: we are currently creating schools, hospitals, offices and urban spaces that are simply not fit for purpose… It's so much easier and cheaper to design in good acoustics, low noise and good sound systems at the start – and yet sound is rarely considered an important element of design, and even if it has been included, so often acoustics and sound systems are the first things to get 'value engineered' out of the project.”
Large room, long reverberation time
As a rule of thumb, it is pretty safe to assume that the larger a room is; the longer the reverberation time will be. Long reverberation times are disruptive for dialogue or work, because the sound has nowhere to go – conversations are difficult and concentration is disturbed.
In large rooms avoid too many parallel surfaces which bounce sound back and forth between ceiling and floor and from wall to wall, creating a longer reverberation time.
Tips to help spread the sound and shorten the reverberation time:
Reducing noise with the right surface angle
When designing large spaces, like open plan offices, it is critical to keep the reverberation time and the general noise level to a minimum. However in such commercial buildings, large glass facades are typical – these hard surfaces reflect sound at the same angle it arrives. The result is a long reverberation time and a noise level so high that people simply cannot concentrate.
Tips to reduce noise levels and reverberation time:
We have established that hard parallel surfaces send sound straight back to the source, so a ceiling that is not parallel with the floor can effectively manipulate sound. The shape of the ceiling is very important to the acoustics in a room and an incorrectly shaped ceiling can be very disruptive to the activity going on in the room.
Tips for ceiling shapes:
Examples:
We know room size is an important factor in determining reverberation time, but it is also significant for the character of the sound. The shape of a room also influences how sound behaves - it is more difficult to predict how sound will behave in a non-rectangular room than in a rectangular room. Some non-rectangular rooms enhance sound quality, while others can create unintended mirror points.
Tips for regulating reverberation time in different sized rooms:
Room height also affects the quantity of sound absorbing material needed.
On a final note it is worth considering rooms that are connected, where the sound in one room can influence the sound in the other. Here an acoustic transition between the rooms helps to ensure that the sound is not perceived as being very different from one room to the other. If the difference is too great, it can feel as if you have cotton wool in your ears as you move between rooms.
Another element that needs consideration when looking at reverberation time is of course the way the space will be used, as different types of usages don’t call for the same reverberation times.
Click here to access Knauf's Reverberation Time Calculator
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