Version HTML de base
Spécial “ Noise at work 2007 ”
29
Acoustique
&
Techniques n° 49
Acoustical evaluation and planning of offices
In large size offices an important part of the resulting noise
level is according to the fisrt item. The required estimation
and qualification is shown in the following example.
Example
The following example shows how an acoustic design for
an open-plan office inside an administrative building can
be applied. Figure 1 shows the layout (only half of the
room is displayed) with 56 workplaces. Each workplace
is supposed to be equipped with a computer and a laser
printer. The areas of different functional groups are marked
with dashed lines.
Basic information
With the dimensions of the room mentioned above each of
the 56 workplaces shares an average area of :
S»= (27 x 21) / 56 m² = 10 m²
(1)
The table 2 shows the sound power levels of the essential
noise sources inside the office. The data approximately
matches the state of the art of year 2000.
Based on the values for planning of table 2 the sound
power level at a workplace with one computer (idling) and
one laser printer (idling) results in:
L
WA,equipment
= {45 (+) 42} dB(A) = 47 dB(A)
(2)
(The symbol (+) indicates the energetic summation of the
levels)
The sound power level of conversations per workplace can
be determined according to relation (3). The determination
is based on the sound power level of a relaxed talking
person with approximately 55dB(A) and an added correction
value dL
part
depending on the part k of persons that are
talking at the same time.
L
WA,speech
= 55 dB(A) + dL
part
(3)
with dL
part
according to following table
Office type
Part k
dL
part
Call center
1
0
Sales department
0,8
-1
Administration
0,25
-6
Design Office
0,1
-10
Table 3 : dLpart for several office utilization
As this example concerns the office type “administration”
it follows:
L
WA,speech
= (55 – 6) dB(A) = 49 dB(A)
(4)
Fig. 1 : Layout of an open-plan office for administration (one half displayed only). The dimensions
are L = 27 m ; B = 21 m ; H = 2,75 m ; a = 1,8 m ; b = 3,5 m ; c = 4 m and d = 5,5 m
Noise source
Range of values Values for
planning
dB(A)
Above
dB(A)
Up to
dB(A)
Speaking person (at the phone)
55
70
65
Computer idling (fan, disk, drive)
30
50
45
Computer disk access
35
55
50
Computer by using keyboard
55
65
60
Laser printer idling
<< 30 46
42
Laser printer printing
55
60
58
Copier idling
50
60
58
Copier printing
60
70
67
Phone ringing
60
80
70
Table 2 : Sound power level LwA of noise sources
that determine the noise level in office