Sound Absorption and Sound Insulation Sound absorption Transmitted energy Converted energy Reflected energy Incident energy Absorption coefficient = converted + transmitted energy a incident energy Absorption - Reverberation Sabine V V a, S T 0.16 aS Large room volume long reverberation High absorption factor short reverberation Large absorption area short reverberation Reverberation time Loudness Time T seconds Measurement of absorption factor The room method EN ISO 354 1 1 A0.16V( ) T T with without A=equivalent absorption area, m2 V V= room volume, m3 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 Thickness: 20 mm Panel size: 1192x592 mm a p, 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 Absorption class A 0,8 Absorption class B 0,6 Absorption class C 0,4 Absorption class D 0,2 Absorption class E 0 Unclassified 125 250 500 1000 2000 4000 Frequency, Hz Practical absorption coefficient and classification Weighted absorption 1,2 coefficient, a w 1 a w = 0,9, class A 0,8 a w = 0,7, class C 0,6 0,4 0,2 Practical sound absorption coefficient 0 125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz Reflected sound L 10log(1a) At absorption The reflected sound class 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 Porous absorbers - Important parameters o.d.s. t - Surface (layer) 1-0 - Material - Thickness - Overall depth of system (o.d.s.) Absorption coefficient Absorption 0 Frequency (Hz) Absorption coefficient - various thickness small overall depth of system 1,2 1 0,8 0,6 0,4 0,2 Practical sound absorption coefficient 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) Absorption coefficient - various overall depth of system 1,2 1 0,8 0,6 0,4 0,2 Practical sound Practicalsound absorption coefficient 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 1 0,8 0,6 alpha 0,4 beta gamma 0,2 Practical Practical sound absorption coefficient 0 125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz Surface layer - upper frequency limit fu Absorption Absorption coefficient Frequency fu 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) Equivalent absorption area (ISO 354) A a A (m2) S Master Solo S (1200x1200), single unit for various o.d.s. 3 2.5 2 1.5 100 mm 200 mm 1 400 mm 600 mm 0.5 800 mm Equivalent absorption area, m2 area, absorption Equivalent 1000 mm 0 125 250 500 1000 2000 4000 Frequency, Hz Master Solo S, array with 9 panels 1200 x 1200, - 600 mm o.d.s., for various distances d 3 d 2.5 d 2 1.5 1 100 mm 300 mm , d , d 0.5 500 mm Equivalent absorption area, m2 area, absorption Equivalent single unit , d 0 125 250 500 1000 2000 4000 Frequency, Hz Calculation of reverberation time S4, S5 Sabine's formula: T = 0.16·V/A 3 S1 V = volume, m S3 A = equivalent absorption area, m2 S2 S6 A=α1∙S1+ α2∙S2+ α3∙S3+ α4∙S4+ α5∙S5+ α6∙S6 Calculation of reverberation time: FHU added S Sabine's formula: 4 S5 T = 0.16·V/A S V = volume, m3 1 S3 A = equivalent absorption area, m2 S2 S6 A=α1∙S1+ α2∙S2+ α3∙S3+ α4∙S4+ α5∙S5+ α6∙S6 + 6∙AFHU Calculation of sound pressure level decrease with FHU AFHU S4 S5 A A L 10log( 0 ) A0 S1 S3 S2 S6 A0 =α1∙S1+ α2∙S2+ α3∙S3+ α4∙S4+ α5∙S5+ α6∙S6 A=6∙AFHU Sound insulation Different sound sources demands different sound insulation Sound sources spectral and eiiih! temporal characteristics Speech X X X X Footstep Music Installation Traffic Impact sound - definition and measurement procedures Impact sound transmission Ln = Lr + 10 log (A/10) (dB) Tapping High Ln high impact sound machine transmission Low Ln low impact sound transmission Lr A L’n denotes a field value Lr: Sound pressure level receiving room A: Equivalent absorption area Tapping machine Airborne sound, definition and measurement procedures Sound reduction Lr R = Ls- Lr- 10 log(A/S) (dB) Ls S A High R High sound insulation Low R Low sound insulation Ls: Sound pressure level sending room Lr: Sound pressure level receiving room A: Equivalent absorption area R’ denotes a field value S: Area separating wall Airborne sound insulation 70 Mass law 60 6 dB/octave Doubled weight leads to 6 dB 50 increased insulation 40 concrete leight-weight wall 30 mineral wool soundreduction (dB) 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: Dn,f,w – weighted normalized flanking level difference Supersedes ISO 140-9:1985 (Dn,c,w) Definition and measurement procedure A Ls Lr 2 Dn,f = Ls- Lr- 10 log(A/A0) A0=10 m (dB) Ecophon Combison™ Sound insulation plus sound absorption D 40 dB Combison n,f,w Uno A Dn,f,w 42 dB D 41 dB n,f,w Combison Dn,f,w 40 dB Uno D Combison Duo A Combison Duo E 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) 3150 100 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 .