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RumsakustikErling Nilsson, Akustiker

ECOPHON Saint-Gobain

Community school no 15, Gdynia, Poland. Architect: Adam Drochomiercki. Photo: Szymon Polanski.

System: Ecophon Master A/alpha

Hospital Spital św. Zofii, Warsaw, Poland. System: Ecophon Hygiene Advance

Axel Springer AG, Hamburg, Germany. Photo: Eric Shambroom. System: Ecophon Light coffer with Focus E.

Restaurang Restaurangen, Stockholm. Architect: Mattias Ljunggren. Photo: Åke E:son Lindman.

System: Focus D with Connect Shadow channel trim

• SWIMMINGPOOL

Miejska Sala Widowiskowo-Sportowo, Community Sports Hall. Architect: Przedsibiorstwo Projektowo-Wykonawcze

pro-Art KONOPKA. Photo: Szymon Polanski. System: Ecophon Focus DG

Sultan Ahmad State Mosque, Kuantan, Malaysia. System: Ecophon Gedina.

Örat

Hörselsnäckan

Hair cells in cochlea: a) In healthy conditions

b) With ongoing damage by noise, gluing together.

c) With ongoing damage by noise, loss of stiffness.

d) Complete degeneration, hair cells broken off.

Skador på hårcellerna i örat

Hörseltest

Did you .ee

the .portmaga.ine

last .aturday?

Audiogram

Normal hörsel

Hörselskada

Kerstin Persson Waye, Occupational and Environmental Medicine, Gothenburg University

Gränsvärden för att undvika hörselskador

• 75 dB LAeq 8 timmar – anses som en riskfri nivå

• 85 dB LAeq 8 timmar, riktvärde i många länder

• 130-150 dB peak – ökad risk för hörselskada

Kerstin Persson Waye, Occupational and Environmental Medicine

Gothenburg University

annoyance, disturbance

Effects in the occupational environment

due to noise

performance and learning

speech interference

tiredness

lower job satisfaction

social interaction

hearing impairment, tinnitus

Wallace Clement Sabine(June 13, 1868 – January 10, 1919)

American physicist who founded the field

of architectural acoustics

Definition: Reverberation time

Sound pressure level, dB

Time, seconds

60 dB

T60

His formula

where

T=the reverberation time (s)

V=the room volume (m3)

A=the total equivalent absorption area (m2 sabin)

where

A

VT 16.0

T

VA 16.0

or

The equivalent absorption area A for a surface with area S m2

is equal to α x S where α is the absorption coefficient for the

surface

Standards and regulations

Absorption coefficient at normal incidence

AbsorberIncident sound energy

Reflected sound energy

Absorbed sound

energy

𝐴𝑏𝑠𝑜𝑟𝑝𝑡𝑖𝑜𝑛 𝑐𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡 𝛼 =𝐴𝑏𝑠𝑜𝑟𝑏𝑒𝑑 𝑠𝑜𝑢𝑛𝑑 𝑒𝑛𝑒𝑟𝑔𝑦

𝐼𝑛𝑐𝑖𝑑𝑒𝑛𝑡 𝑠𝑜𝑢𝑛𝑑 𝑒𝑛𝑒𝑟𝑔𝑦

Absorption coefficient as a function of frequency

20 mm glass wool absorber directly mounted in front of a hard surface (concrete)

Impedance tube (Kundt’s tube)

Lmax (dB)

Lmin (dB)

𝐹 = 10(𝐿𝑚𝑎𝑥−𝐿𝑚𝑖𝑛)/20

𝛼 =4𝐹

(1 + 𝐹)2

Absorber

Standing wave

Absorption coefficient

AbsorberIncident sound energy at angle θ

θ

θ

Reflected sound energy at angle θ

Absorbed sound

energy at angle θ

𝐴𝑏𝑠𝑜𝑟𝑝𝑡𝑖𝑜𝑛 𝑐𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡 𝛼(𝜃) =𝐴𝑏𝑠𝑜𝑟𝑏𝑒𝑑 𝑠𝑜𝑢𝑛𝑑 𝑒𝑛𝑒𝑟𝑔𝑦 𝑎𝑡 𝑎𝑛𝑔𝑙𝑒 𝜃

𝐼𝑛𝑐𝑖𝑑𝑒𝑛𝑡 𝑠𝑜𝑢𝑛𝑑 𝑒𝑛𝑒𝑟𝑔𝑦 𝑎𝑡 𝑎𝑛𝑔𝑙𝑒 𝜃

Sound absorption as a function of incidence angle

θ

20 mm glass wool absorber directly mounted in front of a hard surface (concrete)Frequency: 1000 Hz

Reflected sound

0,30 – 0,55 (class D) 1-4 dB

0,60 – 0,75 (class C) 4-7 dB

0,80 – 0,85 (class B) 7-10 dB

0,90 – 0,99 (class A) 10-20 dB

The reflected sound is

reduced by

Absorption

coefficient

)1log(10 L

Lincidence

Lreflected ΔL = Lincidence- Lreflected (dB)

Glass wool

Open and closed structures

Closed cell Open cell Simple model

of porous

absorber

Microscopic structure

Friction

Sabine formula

where

T=the reverberation time (s)

V=the room volume (m3)

A=the total equivalent absorption area (m2 sabin)

where

A

VT 16.0

T

VA 16.0

or

The equivalent absorption area A for a surface with area S m2

is equal to α x S where α is the absorption coefficient for the

surface

Acoustic design with Sabine formula

A(before treatment)=0,161xV/T= 0,161x200/2,5=12,9 m2 sabin

A(needed to fulfil 0,40 s)= 0,161xV/T=0,161x200/0,40=80,5 m2 sabin

A( to be added to fulfil 0,40 s)=A(needed)-A(before)=80,5-12,9=67,6

m2 sabin

Example: The reverberation time in a room with a volume of 200 m3

is 2,5 s at 1000 Hz.

Target value for the reverberation time is 0,40 s at 1000 Hz

If e.g. the absorption coefficient for a ceiling absorber is 0,90 at 1000 Hz

we will need S= A/α=67,6/0,90=75 m2

Sabine formula: How it works in theory

Absorption coefficients (500 Hz):

Walls=0,15

Ceiling=0,80

Floor=0,10

Absorption data from EN 12354-6

Absorption data from EN 12354-6

Sabine formula: How it works in theory

Absorption coefficients (500 Hz):

Walls=0,15

Ceiling=0,80

Floor=0,10

A=∑αi x Si = 0,10x6x7,5+2x0,15x7,5x2,5+2x0,15x6x2,5+0,80x6x7,5=51 m2 sabin

T60=0,161x(V/A)=0,161x112,5/51≈0,36 s

On the use of practical absorption coefficients

On the use of practical absorption coefficients

S,

VA=equivalent absorption area, m2 sabine

V= room volyme, m3

T= reverberation time, s

absorption coefficient

α = ΔA/S

Measurement of absorption coefficients

according to EN ISO 354

α

withoutT

V

withT

VAAA

withoutwith

16.016.0

FHU - Acoustic specification

S

A

Equivalent absorption area (ISO 354)

A (m2)

Absorption factor (ISO 354)

S ?

Absorbent ceiling FHU – free hanging unit

V

Reverberation chamber

)11

(16.0

withoutT

withT

VA

AFHU =A/6

Free hanging units “Solo”

Typical classroom

Effect of furniture

absorption

scattering

No boxes

Boxes on the wall

Sabine

Scattering – why is it important?

Glass wool

Reflection from a surface

Specular reflection

–Angle of reflection equals

angle of incidenceθ

θ

Incident sound

energy, Iinc

Reflected sound

energy, Irefl

Absorption coefficient:

𝛼 =𝐼𝑖𝑛𝑐 − 𝐼𝑟𝑒𝑓𝑙

𝐼𝑖𝑛𝑐=

𝐼𝑎𝑏𝑠𝐼𝑖𝑛𝑐

Reflection from a surface

Specular reflection

–Angle of reflection equals

angle of incidence

Diffuse reflection

–Scattered in many

directions

Reflection from a surface

Scattering coefficient, s

• Fraction of energy which is scattered

• Always between 0 and 1

Absorption and scattering

𝛼 + 1 − 𝛼 ∙ 1 − 𝑠 + 1 − 𝛼 ∙ 𝑠 = 1

absorbed specularly reflected diffusely reflected

Simulation of sound fields

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Room Acoustic Comfort

Assessment of sound in rooms

Sound source

Physical regionPhysiological and psychological region

Room

Sensation• Sound strength• Clarity• Sharpness• …

Preference

Assessment of sound in rooms

Room types

Reverberant room

(Sabine room)

Open-plan spaces

Corridors

Room with absorbent

ceiling

An approach to create room acoustic comfort

Sensation of sound

Several room acoustical

descriptors

Characterisation of

room types

Room acoustic requirements

adapted for the activity

People Room

Activity

Reverberance: EDT, T20, T30

Speech inelligibility: C50, STI

Strength of sound: G, SPL

Sound propagation: DL2, DLf

Reverberant rooms

industrial spaces,

central stations,

cathedrals

Ordinary rooms with absorbent ceilings

class rooms,

offices,

health care premises

dining rooms,

conference rooms,

day-care centres

Rooms with extended forms

open-plan offices,

corridors

Education

Machinery noise

Noisy activities

Office sounds

Music

Room acoustic quality aspects

• Reverberation

• Speech clarity

• Auditory strength

• Spatial decay

Efterklang

• Relaterar till hur snabbt ljudenergin försvinner i ett rum

Lång efterklang

Kort efterklang

Taltydlighet

• Relaterar till hur tydligt tal uppfattas

Otydligt

Tydligt

Ljudstyrka

• Upplevelsen av ljudets styrka

Hög ljudnivå

Låg ljudnivå

Ljudets avståndsdämpning

• Ljudnivån avtar med avståndet från ljudkällan.

Tal på 1 meters avstånd

Tal på 4 meters avstånd

Tal på 8 meters avstånd

Reverberation

Speech Clarity

Auditory Strength

Spatial decay

Early Decay Time (EDT), T20, T30 (ISO 3382-1/2)

C50 , U50, STI (ISO 3382-1, IEC 60268-16)

Sound Strength G (ISO 3382-1)

D2,S , Lp,A,S,4m , STI (ISO 3382-3)

Human qualities – objective descriptors

Useful reflections

Detrimental reflections

)end)Energy(50

50ms)Energy(0log(10C50

, dB

Definition of room acoustic measures: Speech Clarity C50 (dB)

Room acoustic measures: Sound strength G (dB)

G = LpRoom – Lp10m =Lp – Lw + 31 dB (omni-directional sound source)

10 m

Subjective listener

aspect

Room acoustic

quantity

Just noticeable

difference

Subjective level of

sound

Sound Strength G in dB 1 dB

Perceived

reverberance

Reverberation time T20 in

seconds

5%

Perceived clarity of

sound

Speech Clarity C50 in dB 1 dB

Just noticeable difference of room acoustic quantities

according to ISO 3382-1

Microphone

Loudspeaker

Reverberation

time, T20

Speech

clarity, C50

Sound

Strength, G

Impulse response

time, s

Room acoustic measurements

Dining/meeting room at a hospital in Landskrona, Sweden.

• It echoes a lot.

• If you sit in the middle of the room you

can’t participate in any conversation at

all.

• I just take shorts breaks and avoid

having lunch together with others.

• Sometimes you have to ask people to

repeat what they said.

• There is an incredible din that

prevents you from talking, even with

the person sitting next to you, when

there are a lot of people here.

• I leave the room as fast as possible.

Dining/meeting room at a hospital in Landskrona, Sweden.

Room dimension

Volume = 68 m3

Floor area = 25 m2

Acoustic refurbishment

• Ceiling: Master B

• Wall: Wall Panel C/Texona (2700 x 1200)

0

0,2

0,4

0,6

0,8

1

1,2

125 250 500 1000 2000 4000

Frequency Hz

Pra

cti

cal

so

un

d a

bso

rpti

on

co

eff

icie

nt

Acoustic treatment of dining/meeting room

Room acoustic measurements

1. before acoustic treatment

2. for the room with ceiling treatment only and

3. for the ceiling treatment in combination with the wall panel

Table 2. Result of measurements at Landskrona Hospital

Parameter Before

acoustic

treatment

Only acoustic

ceiling

Acoustic ceiling

and wall panel

Average 500 and 1000 Hz

Average 500 and 1000 Hz

Average 500 and 1000 Hz

T20 [s] 0.76 0.37 0.27

∆L [dB]* - -8 -8

C50 [dB] 1.8 8.6 12.0

D [%] 60 88 94

RASTI ** 0.66 0.82 0.87

* * ΔL is the reduction of sound levels in the room compared to the untreated room.

**Room Acoustic Speech Transmission Index according to IEC 60268-16

Some comments from the staff after the refurbishment

• Much more subdued environment. I feel more relaxed in the room.

• It’s easier to talk to each other.

• There’s less din when a lot of people are in the same room.

• There are less echoes in the room.

• A lot of people can talk simultaneously in different parts of the room without a

problem.

Acoustics extremes

Anechoic chamber

Reverberation chamber

Equaliser: Balanced sound for optimal room

acoustics

T20 (s) (250 – 4000 Hz) G (dB)

0,20

0,30

0,80

0,50

0,60

0,70

1,00

1,10

1,20

1,30

0,90

7

8

13

9

10

11

12

15

16

17

18

14

D50 (%)

50

56

80

61

67

72

76

86

89

91

93

83

Reverberation Sound strength Speech clarity

T20 (s) (125 Hz)

0,20

0,30

0,80

0,40

0,50

0,60

0,70

1,00

1,10

1,20

1,30

0,90

Example: Classroom, traditional education

1,40

1,501,50

1,40 19

20

44

94

0,40