Numerical study on the repeatability and reproducibility ...

Arne Dijckmans, Lieven De Geetere, Bart Ingelaere – 4th ABAV Acoustics Research Day, 21-03-2018 -

Numerical study on the repeatability and reproducibility of laboratory building acoustic measurements

Arne Dijckmans, Lieven De Geetere, Bart Ingelaere

Belgian Building Research Institute (BBRI)

4th ABAV Acoustics Research Day21 March 2018, Brussels


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Laboratory building acoustic measurements◘ Sound reduction index (ISO 10140)

◘ Vibration reduction index (ISO 10848)

◘ The measurements trust on simplified statistical relations

10 log

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2 10 log

,


Issues at low frequencies◘ Repeatability

Variation of results in same laboratory Source and sensor positions, averaging time, reverberation time, …

◘ Reproducibility Differences between measurements at different test facilities Geometry (modal behaviour)

Pedersen et al. (2002)

Double window 6‐16‐6 mm

Measurement results at 4 different laboratories


Building acoustical standards◘ Requirements for test facilities

ISO 10140-5:2010 Acoustics – Laboratory measurement of sound insulation of building elements – Part 5: Requirements for test facilities and equipment

◘ Measurement procedures and installation of test panels ISO 10140-1:2010 Acoustics – Laboratory measurement of sound insulation of building

elements – Part 1: Application rules for specific products ISO 10140-4:2010 Acoustics – Laboratory measurement of sound insulation of building

elements – Part 4: Measurement procedures and requirements

◘ Improved measuring procedures (intensity measurements) ISO 10186-1:2000 Acoustics – Measurement of sound insulation in buildings and of

building elements using sound intensity – Part 1: Laboratory measurements ISO 10186-3:2002 Acoustics – Measurement of sound insulation in buildings and of

building elements using sound intensity – Part 1: Laboratory measurements at low frequencies

◘ Uncertainty ISO 12999-1:2014 Acoustics – Determination and application of measurement

uncertainties in building acoustics – Part 1: Sound insulation


Contents◘ Introduction

◘ Airborne sound insulation measurements Wave based model Repeatability Reproducibility

◘ Flanking transmission measurements Wave based model Repeatability Reproducibility


Airborne sound insulation measurements◘ Wave based transmission suite model

Direct sound transmission between rooms No flanking

◘ Sound reduction indices 10 log

6 10 log

9 10 log

◘ 7 test panels

Dijckmans (2011)


Repeatability◘ Influence of microphone positions

Simulation Lpr at 100 Hz Measurement Lpr at 80 Hz

Hopkins and Turner (2005)Dijckmans (2011)


Repeatability◘ Using more microphone positions doesn’t improve the repeatability below 100 Hz◘ LpS can be determined with higher accuracy, so the repeatability of RIS will be better

Simulation Lpe and Lpr20 sets of 5 or 10 microphone positions

Simulation LpSSmall test element (1.25 m x 1.5 m):10 sets of 6 microphone positions

Large test element (3.25 m x 2.95 m): 10 sets of 12 microphone positions


Repeatability◘ Repeatability error related to source position is larger

◘ Doubling the number of source positions will improve the repeatability

R RI RIS

Difference Δσ = σ2 ‐ σ4 for 20 sets of 2 or 4 source positions

Simulation for 20 sets of 2 source positions

R RI RIS


◘ 5 different test facilities, two directions of transmission

Reproducibility

Wave based models for small test elements

CSTBPTB IBP

KU LeuvenDELTA


◘ 5 different test facilities, two directions of transmission

Reproducibility

Wave based models for large test elements

CSTBPTB IBP

KU LeuvenDELTA


◘ The reproducibility uncertainty is larger than the repeatability uncertainty◘ For small test elements, RIS has the best reproducibility◘ For large heavy walls, RI and RIS has the same reproducibility as R

Reproducibility

Simulation for 5 different test facilities using 2 source positions

R RI RIS


◘ Doubling the number of source positions will not improve the reproducibility

Reproducibility

R RI RIS

Difference Δσ = σ2 ‐ σ4 for 5 test facilities when using 2 or 4 source positions


Relative importance of geometrical parameters

Aperture dimensions (niche effect):◘ Staggered niche with step 60 or 65 mm◘ Total niche depth of 400, 410 or 420 mm◘ Smaller niche depth of 185, 190 or 195 mm


◘ Similar uncertainty for all geometrical parameters◘ Use of intensity method will decrease the influence of these parameters◘ Uncertainty for double glazing is larger than for single glazing

Small test elements

Double glazing 10‐18‐12 mm

R RI RIS

Single glazing 4 mm

R RI RIS


◘ Uncertainty caused by plate dimensions is the most important◘ Influence plate dimensions cannot be decreased by use of intensity methods◘ Global uncertainty is the same for the three measurement methods

Large walls (low modal density)

Concrete wall 15 cm

R RI RIS

Sand limestone wall 15 cm

R RI RIS


Large walls, high modal density◘ Influence of plate dimensions is less important (~ room dimensions)◘ Only influence of room dimensions is decreased by use of intensity methods◘ Global uncertainty of intensity methods will be slightly better

Double plasterboard wall 3x12.5‐100‐3x12.5 mm

R RI RIS

Gypsum block wall 7 cm

R RI RIS


Contents◘ Introduction

◘ Airborne sound insulation measurements Wave based model Repeatability Reproducibility

◘ Flanking transmission measurements Wave based model Repeatability Reproducibility


Flanking transmission measurements◘ Wave based model

Structure-borne sound transmission Rigid junctions of single and double walls

◘ Vibration reduction index

◘ Repeatability and reproducibility study Double wall T-junction 15 cm concrete floors (4 m x 5 m) 10 cm concrete walls (4 m x 3.5 m), air cavity 5 cm

, ,

2 10 log

,

,

Dijckmans (2016)


Repeatability: source positions◘ Influence of source position is important when the modal overlap factor is smaller

than 1 (f < 1000 Hz)

Simulation for 20 different sets of 3 source positions


Reproducibility: plate dimensions◘ Larger uncertainty due to plate dimensions◘ Influence is important when the modal overlap factor is smaller than 1 (f < 1000 Hz)

Simulation for 210 plate junctions with varying wall height (H = 3 – 5 m), varying floor length (L = 3 – 5 m) or varying junction length (W = 3 – 5 m)

W

H

L L


Conclusions◘ Airborne sound insulation measurements

Repeatability of intensity methods better than that of the pressure method Increasing the number of source positions will increase the repeatability, but

will not increase the reproducibility significantly Reproducibility is determined by differences in geometrical parameters

▪ The influence of receiving room dimensions is smaller for RI and RIS

▪ The influence of source room dimensions, aperture position and aperture dimensions is smaller for RIS

▪ For large elements with low modal density, the variation in plate dimensions is determining the global reproducibility uncertainty

◘ Flanking transmission measurements Limited amount of literature on repeatability and reproducibility of Kij

Large influence of source positions and plate dimensions when modal overlap factor is smaller than 1

Difficult to draw conclusions based on a single deterministic measurement for heavyweight junctions


Thanks for your attention

4th ABAV Acoustics Research Day21 March 2018, Brussels

Numerical study on the repeatability and reproducibility ...

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