Sound Absorption and Sound Insulation

Transcription

1 Sound Absorption and Sound Insulation

2 Sound absorption Transmitted energy Converted energy Reflected energy Incident energy

3 Absorption coefficient a = converted + transmitted energy incident energy

4 Absorption - Reverberation Sabine T 0.16 V S a a, S V Large room volume High absorption factor Large absorption area long reverberation short reverberation short reverberation

5 Reverberation time Loudness Time T seconds

6 Measurement of absorption factor The room method EN ISO A 0.16V ( T with 1 ) T without V A=equivalent absorption area, m 2 V= room volume, m 3 S absorption factor Α = A/S Reverberation chamber

7 Ecophon ceiling Akutex T Gedina edge A Thickness: 20 mm Panel size: 1192x592 mm Frequency Curve

8 Ecophon ceiling Akutex T Gedina edge A a p, Thickness: 20 mm Panel size: 1192x592 mm Frequency Curve

9 Classification of sound absorbers EN-ISO a p Practical sound absorption coefficient 1,0 0,8 0,6 0,4 0,2 0 Absorption class A Absorption class B Absorption class C Absorption class D Absorption class E Unclassified Frequency, Hz

10 Practical sound absorption coefficient Practical absorption coefficient and classification Weighted absorption coefficient, a w 1,2 a w = 0,9, class A 1 a w = 0,7, class C 0,8 0,6 0,4 0, Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz

11 Reflected sound L 10 log(1 a) At absorption class The reflected sound is reduced by D 1-4 db C 4-7 db B 7-10 db A db

12 Absorbers 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

13 Absorption coefficient Porous absorbers - Important parameters o.d.s. t Surface (layer) - Material - Thickness - Overall depth of system (o.d.s.) 0 Frequency (Hz)

14 Practical sound absorption coefficient Absorption coefficient - various thickness small overall depth of system 1,2 1 0,8 0,6 0,4 0, Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz Thickness = 40 mm (o.d.s. = 40 mm) Thickness = 20 mm (o.d.s. = 20 mm)

15 Practical sound absorption coefficient Absorption coefficient - various overall depth of system 1,2 1 0,8 0,6 0,4 0, Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz o.d.s. = 200 mm (t = 20 mm) o.d.s. = 100 mm (t = 20 mm) o.d.s. = 50 mm (t = 20 mm)

16 Master A, o.d.s. 200 mm 1,2 Practical sound absorption coefficient 1 0,8 0,6 0,4 0,2 alpha beta gamma Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz

17 Absorption coefficient Surface layer - upper frequency limit f u Frequency f u 4000 Hz radius (mm) perforation (%)

18 FHU - Acoustic specification Absorbent ceiling FHU free hanging unit S? Absorption factor (ISO 354) a A S Equivalent absorption area (ISO 354) A (m 2 )

19 Equivalent absorption area, m2 Master Solo S (1200x1200), single unit for various o.d.s mm mm 400 mm 600 mm mm 1000 mm Frequency, Hz

20 Equivalent absorption area, m2 Master Solo S, array with 9 panels 1200 x 1200, mm o.d.s., for various distances d d d mm 300 mm 500 mm single unit Frequency, Hz, d, d, d

21 Calculation of reverberation time S 4, S 5 Sabine's formula: T = 0.16 V/A S 1 S 3 V = volume, m 3 A = equivalent absorption area, m 2 S 2 S 6 A=α 1 S 1 + α 2 S 2 + α 3 S 3 + α 4 S 4 + α 5 S 5 + α 6 S 6

22 Calculation of reverberation time: FHU added S 1 S 4 S 5 S 2 S 3 Sabine's formula: T = 0.16 V/A V = volume, m 3 A = equivalent absorption area, m 2 S 6 A=α 1 S 1 + α 2 S 2 + α 3 S 3 + α 4 S 4 + α 5 S 5 + α 6 S A FHU

23 Calculation of sound pressure level decrease with FHU A FHU S 1 S 4 S 3 S 5 L 10 log( A0 A 0 A ) S 2 S 6 A 0 =α 1 S 1 + α 2 S 2 + α 3 S 3 + α 4 S 4 + α 5 S 5 + α 6 S 6 A=6 A FHU

24 Sound insulation Different sound sources demands different sound insulation eiiih! X X X X Sound sources spectral and temporal characteristics Speech Footstep Music Installation Traffic

25 Impact sound - definition and measurement procedures Impact sound transmission L n = L r + 10 log (A/10) (db) Tapping machine High L n high impact sound transmission L r A Low L n low impact sound transmission L n denotes a field value L r : Sound pressure level receiving room A: Equivalent absorption area

26 Tapping machine

27 Airborne sound, definition and measurement procedures Sound reduction L s S A L r R = L s - L r - 10 log(a/s) (db) High R Low R High sound insulation Low sound insulation L s : Sound pressure level sending room L r : Sound pressure level receiving room A: Equivalent absorption area S: Area separating wall R denotes a field value

28 Airborne sound insulation Mass law 6 db/octave Doubled weight leads to 6 db increased insulation sound reduction (db) concrete leight-weight wall mineral wool frequency (Hz)

29 Sound transmission paths

30 Room-to-room airborne sound insulation of a suspended ceiling with a plenum above EN ISO : D n,f,w weighted normalized flanking level difference Supersedes ISO 140-9:1985 (D n,c,w )

31 Definition and measurement procedure A L s L r D n,f = L s - L r - 10 log(a/a 0 ) A 0 =10 m 2 (db)

32 Ecophon Combison Sound insulation plus sound absorption Combison Uno A D n,f,w 40 db D n,f,w 42 db D n,f,w 41 db Combison Uno D D n,f,w 40 db

33 The effect of additional absorbers Example: Increase in sound reduction in laboratory Combison XR 600 mm on each side of the partition about 3 db Ecophon Combison about 6-12 db about 6 db Combison XR all over the suspended ceiling Combison Barrier over the partition

34 How does the location of the absorbers influence sound insulation? R (db)

35 What happens when different panels are mixed in a ceiling? R (db)

36 The effect of barriers D n,f (db)

37 Influence of ducts and gaps 15% openings in the barrier showed a reduction of sound insulation by 1 db for a D n,f,w = 40 db R (db)