Acoustic design of industrial spaces

7/28/2019 Acoustic design of industrial spaces

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Acc a acT rduti f is lvls ad iras f rduti


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1. Introduction

2. Acoustic measurements

3 Effect of acoustical treatment with suspended ceilingand wall panels

> Acoustic design with wall panels

> Positioning of wall panels

> Case study

4. Case Study: Oatly Health Products Facility

> Room> Activity

> Acoustic design

> Room acoustic measurements

> Results

> Additional actions

6. Appendix 1 Results of measurements before and after

e c o p h o n : A C o u s t i C d e s i g n o f i n d u s t r i A l s pA C e s


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e c o p h o n : A C o u s t i C d e s i g n o f i n d u s t r i A l s pA C e s 2

Acc Mam

To objectively measure the acoustic conditions in an industrial space

several room acoustic parameters have to be measured. Its common

to measure parameters related to reverberance, sound strength and

speech clarity.

The parameters are described in table 1.

TABLE 1

Parameter Designation Unit Explanation Standard

Reverberationtime

T20 sSpeed atwhich sounddisappears

ISO3382-1/2

SpeechClarity

C50 or D dB or %

Measure theperceptiono speechin a room. Ithese valuesincreasethe speechintelligibilityincreases.

ISO3382-1/2

Sound leveldecrease

L dB

Measure thedecreasein soundpressure level

To objectively measure the acoustic conditions in an

industrial space several room acoustic parameters

have to be measured.


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c a wa a

Its very important to keep in mind that acoustical treatment with

acoustic suspended ceilings and wall absorbers in industrial spaces

mainly infuences the general noise level. The sound eld normally

consists o direct sound and a reverberant sound. The direct part

reaches the operators ears without hitting the room suraces.

Thus, this part is not aected by the acoustic ceiling and wall panels.To decrease the direct sound you oten have to use screens, hoods or

changing the mechanical process that generates the sound.

The sound level that originates rom the reverberant sound will be

aected by the absorbing ceiling and wall panels. A realistic goal

concerning the reduction o the dB(A) level in the reverberant eld by

adding porous absorbers is in the region 5 to 10 dB(A).

The perception o change in sound pressure level is given in table 2.

TABLE 2

Changes in sound level Subjective perception

1 dBReduction or increase is hardly

perceivable

5 dBReduction or increase is clearly

perceivable

10 dBReduction or increase results in

halving or doubling o perceivedsound level

Only the noise that originates from the reverberant

sound will be affected by the absorbing ceiling

and wall panels.


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0

0

1

2

3

4

5

6

7

8

50 100

Added amount of absorbers (m2)

alphaw=0.95 (Class A)

Soundl

evelreduction

dB

150 200 250 300 350 400

2s

3s

4s

Figure 1. The eect o added absorbers on the sound level in a

room with a volume o 2000 m3. The gures in the diagram reer

to the reverberation time beore acoustical treatment.

0

0

1

2

3

4

5

6

7

8

9

10

200

Added amount of absorbers (m2).

Soundl

evelreduction

dB

400 600 800 1000 1200

Figure 2. The sound reduction in an industrial space with a foor

area o 250 m2 and or two dierent ceiling heights.

ceiling height 4.5 m, foor area 250 m2


The eect o added absorption in an industrial space is illustrated in

Figure 1. The eect o the acoustic treatment depends on the amount

o absorption beore treatment. In Figure 1 the eect o additional

absorption is measured by the reverberation time. I the space is very

reverberant and consequently has a long reverberation time, the eect

o added absorption will be higher compared to a space with shorter

reverberation time.

Figure 1 reers to an industrial space with a volume o 2000 m3.

In Figure 2 below the eect o added absorption is calculated or an

industrial space with foor area 250 m2 and or two dierent ceiling

heights. The room without added absorbers is supposed to have a

reverberation time o 2 seconds. The alpha w or the added absorbers

is 0.95. When the amount o added absorbers exceeds the foor area

it is assumed that the absorbers are attached to the walls.


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Its common in industrial spaces that the reverberation time at low

requencies is lower than the reverberation time at high requencies.This is illustrated in gure 4. The actory in this case is a ood producer

and the volume o the space is 5760 m3. This also means that acoustic

treatment with porous absorbers will be very ecient since there is a

lot o high requency energy that will be absorbed by the absorbing

ceiling and wall panels.

2

1,5

1

0,5

0125 250 500 1K 2K 4K [Hz]

stdev

Figure 4. Reverberation time or the octave-band requencies 125

to 4000 Hz measured in a ood actory beore acoustic treatment

0

0

1

2

3

4

5

6

7

8

9

10

200

Added amount of absorbers (m2).

Sou

ndl

evelreduction

dB

400 600 800 1000 1200 1 600 1400 1800

Figure 3. The sound reduction in an industrial space with a foor

area o 500 m2 and or two dierent ceiling heights.


ceiling height 8m, foor area 500 m2

Its not uncommon in industrial spaces that the

reverberation time at low frequencies are lower than

the reverberation time at high frequencies.


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Acoustic design with wall panels

From an acoustic point o view its oten advantageous to locate

the absorbing material as close to the noise sources as possible. In

this case an acoustic wall panel may be useul. I there is a risk or

mechanical impact the panel could be protected by a cage. Normally,

the wall panels works as a complement to a suspended ceiling.

Positioning of wall panels

The reduction o sound pressure level is related to the amount o

absorbing material that is added to the room. When reducing sound

pressure, the location o absorbers is o minor importance. However,

when we are concerned with reducing reverberation time and

improving speech clarity the distribution o the absorbers is important.

Even a small quantity o wall panels in a room with absorbent ceiling

could have a great infuence on reverberation time and speech clarity.

Its preerable to cover two adjacent walls with panels rather than two

parallel walls to have the greatest eect on reducing reverberation

within a room.

Field study

In the appendix the eect o acoustic treatment with a suspended

ceiling and wall panels is shown or a actory building.


The reduction of sound pressure level is related tothe amount of absorbing material that is added to

the room.

The effect of acoustic treatment with a

suspended ceiling and wall panels is shown for

a factory building.


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Measurement results in octave bands beore and ater treatment

EDT (s)

EDT [s]

Beore Ater

63 1,0 1,2

125 1,3 0,9

250 1,8 0,7

500 2,3 0,6

1000 2,4 0,6

2000 1,9 0,6

4000 1,6 0,7

T20 (S)

T20 [s]

Beore Ater

63 1,6 1,5

125 1,7 1,1

250 2,0 0,8

500 2,5 0,6

1000 2,4 0,6

2000 1,9 0,6

4000 1,7 0,6

Ax 1 r

mam b a a

Frequency (Hz)

Earlydecaytime(s)

63 125 250 500 1000 2000 40000

0,5

1

1,5

2

2,5

EDT (S) Before EDT (S) After

Frequency (Hz)

Reverberation

(S)

63 125 250 500 1000 2000 40000

0,5

1

1,5

2

2,5

3

T20 (S) Before T20 (S) After


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Acoustic design of industrial spaces