Sound Absorption and Sound

Insulation

Transmitted energy

Reflected energy

Converted

energy

Incident energy

Sound absorption

Absorption coefficient

a = converted + transmitted energy

incident energy

Sabine

Large room volume long reverberation

High absorption factor short reverberation

Large absorption area short reverberation

a, S

V

Absorption - Reverberation

S

VT

a16.0

T seconds

Time

Loudness

Reverberation time

S

V

Reverberation chamber

Measurement of absorption factor

)11

(16.0

withoutT

withT

VA

A=equivalent absorption area, m2

V= room volume, m3

absorption factor

Α = A/S

The room method EN ISO 354

Thickness: 20 mm

Panel size: 1192x592 mm

Frequency Curve 1

50 0.12

63 0.13

80 0.17

100 0.34

125 0.34

160 0.59

200 0.75

250 0.82

315 0.87

400 0.94

500 1.00

630 0.92

800 0.86

1000 0.82

1250 0.94

1600 0.93

2000 0.97

2500 0.99

3150 0.93

4000 0.91

5000 0.88

Ecophon ceiling Akutex T Gedina edge A

Thickness: 20 mm

Panel size: 1192x592 mm

Frequency Curve 1 63 0.15

125 0.40

250 0.80

500 0.95

1000 0.85

2000 0.95

4000 0.90

a p,

Ecophon ceiling Akutex T Gedina edge A

125 250 500 1000 2000 4000

Absorption class A

Absorption class B

Absorption class C

Absorption class D

Absorption class E

Unclassified

Frequency, Hz

1,0

0,8

0,6

0,4

0,2

0

Classification of sound absorbers EN-ISO 11654

p Practical sound absorption coefficient a

Practical absorption coefficient and

classification

0

0,2

0,4

0,6

0,8

1

1,2

125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz

Pra

cti

ca

l so

un

d a

bso

rpti

on

co

eff

icie

nt

a w = 0,9, class A

Weighted

absorption

coefficient, a w

a w = 0,7, class C

D 1-4 dB

C 4-7 dB

B 7-10 dB

A 10-20 dB

The reflected sound

is reduced by At absorption

class

Reflected sound

)1log(10 aL

1. Porous absorbers

(mineral wool products, porous fibreboard products,

foam plastic, fabric, felt etc)

2. Resonance absorbers

a) Cavity absorbers (Helmholtz absorbers)

b) Membrane absorbers

Absorbers

Absorp

tion c

oeff

icie

nt

1-0

0

Frequency (Hz)

o.d.s. t

- Surface (layer)

- Material

- Thickness

- Overall depth of system

(o.d.s.)

Porous absorbers - Important parameters

Absorption coefficient

0

0,2

0,4

0,6

0,8

1

1,2

125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz

Pra

cti

ca

l so

un

d a

bso

rpti

on

co

eff

icie

nt

Thickness = 40 mm (o.d.s. = 40 mm) Thickness = 20 mm (o.d.s. = 20 mm)

- various thickness small overall depth of system

Absorption coefficient

0

0,2

0,4

0,6

0,8

1

1,2

125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz

Pra

cti

ca

l so

un

d a

bso

rpti

on

co

eff

icie

nt

o.d.s. = 200 mm (t = 20 mm) o.d.s. = 100 mm (t = 20 mm) o.d.s. = 50 mm (t = 20 mm)

- various overall depth of system

Master A, o.d.s. 200 mm

0

0,2

0,4

0,6

0,8

1

1,2

125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz

Pra

cti

cal

so

un

d a

bso

rpti

on

co

eff

icie

nt

alpha

beta

gamma

radius (mm) perforation (%)

0.1 1

0.5 2

1.5 3

Ab

so

rpti

on

co

eff

icie

nt

Frequency

fu

fu 4000 Hz

Surface layer - upper frequency limit

FHU - Acoustic specification

S

Aa

Equivalent absorption area (ISO 354)

A (m2)

Absorption factor (ISO 354)

S ?

Absorbent ceiling FHU – free hanging unit

Master Solo S (1200x1200), single unit for various

o.d.s.

125 250 500 1000 2000 4000 0

0.5

1

1.5

2

2.5

3

Frequency, Hz

Eq

uiv

ale

nt

abso

rptio

n a

rea

, m

2

100 mm

200 mm

400 mm

600 mm

800 mm

1000 mm

d d

, d

, d

, d

Master Solo S, array with 9 panels 1200 x 1200,

- 600 mm o.d.s., for various distances d

125 250 500 1000 2000 4000 0

0.5

1

1.5

2

2.5

3

Frequency, Hz

Eq

uiv

ale

nt

abso

rptio

n a

rea

, m

2

100 mm

300 mm

500 mm

single unit

Calculation of reverberation time

S1

S2

S3

S4, S5

S6

A=α1∙S1+ α2∙S2+ α3∙S3+ α4∙S4+ α5∙S5+ α6∙S6

Sabine's formula:

T = 0.16·V/A

V = volume, m3

A = equivalent absorption area, m2

Sabine's formula:

T = 0.16·V/A

V = volume, m3

A = equivalent absorption area, m2

S1

S2

S3

S4 S5

S6

A=α1∙S1+ α2∙S2+ α3∙S3+ α4∙S4+ α5∙S5+ α6∙S6 + 6∙AFHU

Calculation of reverberation time: FHU added

A=6∙AFHU

Calculation of sound pressure level decrease with FHU

)log(100

0

A

AAL

S1

S2

S3

S4 S5

S6

AFHU

A0 =α1∙S1+ α2∙S2+ α3∙S3+ α4∙S4+ α5∙S5+ α6∙S6

Different sound sources demands different sound insulation

Sound sources spectral and

temporal characteristics

Speech

Footstep

Music

Installation

Traffic

X X X X

eiiih!

Sound insulation

Lr: Sound pressure level receiving room

A: Equivalent absorption area

Impact sound transmission

Ln = Lr + 10 log (A/10) (dB)

High Ln high impact sound

transmission

Low Ln low impact sound

transmission

Impact sound

Tapping

machine

Lr A

L’n denotes a field value

- definition and measurement procedures

Tapping machine

Ls: Sound pressure level sending room

Lr: Sound pressure level receiving room

A: Equivalent absorption area

S: Area separating wall

Sound reduction

R = Ls- Lr- 10 log(A/S) (dB)

High R High sound insulation

Low R Low sound insulation

Ls

Lr

A S

R’ denotes a field value

Airborne sound, definition and measurement procedures

Airborne sound insulation

0

10

20

30

40

50

60

70

100

160

250

400

630

1000

1600

2500

frequency (Hz)

so

un

d r

ed

ucti

on

(d

B)

concrete

leight-weight wall

mineral wool

Mass law

6 dB/octave

Doubled weight leads to 6 dB

increased insulation

Sound transmission paths

Room-to-room airborne sound insulation

of a suspended ceiling with a plenum above

EN ISO 10848-2: Dn,f,w – weighted normalized flanking level difference

Supersedes ISO 140-9:1985 (Dn,c,w)

Definition and measurement procedure

Ls Lr

A

Dn,f = Ls- Lr- 10 log(A/A0) A0=10 m2 (dB)

Ecophon Combison™

Combison

Uno A

Combison

Uno D

Combison

Duo A

Combison

Duo E

Dn,f,w 40 dB

Dn,f,w 40 dB

Dn,f,w 42 dB

Dn,f,w 41 dB

Sound insulation plus sound absorption

The effect of additional absorbers

about 3 dB

about 6 dB

about 6-12 dB

Ecophon Combison

Combison XR 600 mm on each side of the partition

Combison XR all over the suspended ceiling Combison Barrier over the partition

Example: Increase in sound reduction in laboratory

How does the location of the absorbers

influence sound insulation?

R (dB)

100 3150

R (dB)

What happens when different panels are mixed

in a ceiling?

100 3150

The effect of barriers

Dn,f (dB)

100 3150

Influence of ducts and gaps 15% openings in the barrier showed a reduction

of sound insulation by 1 dB for a Dn,f,w = 40 dB

R’ (dB)

100 3150