Sound Absorption and Sound Insulation
Sound absorption Transmitted energy Converted energy Reflected energy Incident energy
Absorption coefficient a = converted + transmitted energy incident energy
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
Reverberation time Loudness Time T seconds
Measurement of absorption factor The room method EN ISO 354 1 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
Ecophon ceiling Akutex T Gedina edge A 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 a p, 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
Classification of sound absorbers EN-ISO 11654 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 125 250 500 1000 2000 4000 Frequency, Hz
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 0,2 0 125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz
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 10-20 db
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
Absorption coefficient Porous absorbers - Important parameters o.d.s. t 1-0 - Surface (layer) - Material - Thickness - Overall depth of system (o.d.s.) 0 Frequency (Hz)
Practical sound absorption coefficient Absorption coefficient - various thickness small overall depth of system 1,2 1 0,8 0,6 0,4 0,2 0 125 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)
Practical sound absorption coefficient Absorption coefficient - various overall depth of system 1,2 1 0,8 0,6 0,4 0,2 0 125 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)
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 0 125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz
Absorption coefficient Surface layer - upper frequency limit f u Frequency f u 4000 Hz radius (mm) perforation (%) 0.1 1 0.5 2 1.5 3
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 )
Equivalent absorption area, m2 Master Solo S (1200x1200), single unit for various o.d.s. 3 2.5 2 1.5 100 mm 1 200 mm 400 mm 600 mm 0.5 800 mm 1000 mm 0 125 250 500 1000 2000 4000 Frequency, Hz
Equivalent absorption area, m2 Master Solo S, array with 9 panels 1200 x 1200, - 600 mm o.d.s., for various distances d 3 2.5 d d 2 1.5 1 0.5 100 mm 300 mm 500 mm single unit 0 125 250 500 1000 2000 4000 Frequency, Hz, d, d, d
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
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 6 + 6 A FHU
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
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
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
Tapping machine
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
Airborne sound insulation 70 60 50 Mass law 6 db/octave Doubled weight leads to 6 db increased insulation sound reduction (db) 40 30 concrete leight-weight wall mineral wool 20 10 0 100 160 250 400 630 1000 1600 2500 frequency (Hz)
Sound transmission paths
Room-to-room airborne sound insulation of a suspended ceiling with a plenum above EN ISO 10848-2: D n,f,w weighted normalized flanking level difference Supersedes ISO 140-9:1985 (D n,c,w )
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)
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
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
How does the location of the absorbers influence sound insulation? R (db) 100 3150
What happens when different panels are mixed in a ceiling? R (db) 100 3150
The effect of barriers D n,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 D n,f,w = 40 db R (db) 100 3150