About sound
The goal is not silence but a balanced sound level. To achieve this in an office environment, the right number of absorbers, evaluated in accordance with international standards, are required. But it also requires an understanding of the whole. Pontus Thorsson from Akustikverkstan shares some of his knowledge.
We are in a small room. Thin, laminated sheets
hang from the high ceiling, and a ways up on the concrete walls,
microphones are placed. The room is a so-called reverberation room.
The sound is amplified by the laminated sheets that break apart the
sound waves. This is clearly noticeable. Even the slightest small
cough echoes.
Pontus Thorsson is a Doctor of Engineering in
acoustics. He shows the floor screens that are in the middle of the
room. He is going to test how well the screens work as absorbers.
He is going to do this by sending out a hissing sound and then
measuring how long the reverberation is. In general, it can be said
that the larger the area, the shorter time it takes for the sound
level to fall. He emphasizes how important it is to work in a
controlled manner and to follow the international measurement
standards. All measurement values must be relevant and
comparable.
Pontus Thorsson says that the general sound level
is often measured in dB(A). A normal conversational tone, for
example, is around 60-70 dB(A) while the level in a classroom can
be between 75-80 dB(A) or more. That is close to the limit for what
is acceptable in accordance with the Swedish Work Environment
Authority. The sound level may never exceed 85 dB(A) as the average
value during a workday. According to Pontus Thorsson high
sound levels can have a very negative effect: "The mood is
affected, as is the stress level. This can lead to serious
consequences." But what material is best for damping sound?
A common filling material is mineral wool. As external material,
cloth work best. Wood reflects sound and causes the absorption
level to sink. Therefore, it is important that it is properly
perforated. Pontus comments on the thickness of the sound-damping
screens:
"You may think that they are too thick, but quite simply, a
certain thickness is required in order for the entire frequency
range of speech to be absorbed effectively."
He illustrates with the screen that is being tested. It is 53 mm
thick and consists of a perforated wood panel that has been covered
with sound-damping mineral wool and cloth.
What is it that is important to think about in
order to achieve a balanced sound level? Naturally, acoustics are
affected by the percentage of sound-damping material, but also by
how furniture is arranged and how people are placed. Pontus
Thorsson explains that you also have to remember that different
types of workplaces have different sound reduction needs:
"It is the perceived sound level that you have to take into
consideration. Some people need a large measure of isolation.
Others can take a higher sound level. For example, you cannot
compare the sound levels in a library with the sound level at a
newspaper editorial office.
It is important that office environments
function in every way. For example, glass is a material that is
often used but it does not absorb sound. At the same time, glass
can be a compromise in order for the work environment not to become
too dark.