through steel-concrete composite floors Beth Paxton, Apex Acoustics - - PowerPoint PPT Presentation

Flanking sound transmission through steel-concrete composite floors

Beth Paxton, Apex Acoustics

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Introduction

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• Popular construction type in

multi-residential developments

• Quick and simple method of

construction

• Minimum amount of building

materials used

• Lightweight partitions built off

concrete slab

The problem

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• Flanking transmission – continuous concrete floors
• Guidance indicates floating floors
• Building Regulations performance achieved between

hotel bedrooms at Site A Object: Reliable model to predict sound transmission

EN 12354-1

• Bastian software used to predict sound

transmission

• Transmission through each flanking path calculated

and the contributions from each path combined.

• Floor flanking path sound reduction index simplifies

to:

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𝑆𝑗𝑘 = 𝑆𝑡𝑗𝑢𝑣 + 𝐸𝑤,𝑗𝑘,𝑡𝑗𝑢𝑣 + 10lg

𝑇𝑡 𝑇𝑗𝑇𝑘 dB

20 30 40 50 60 70 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 Standardised level difference, DnT, dB Frequency, Hz Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 Test 7 Test 8 Test 9 Test 10 Test 11 Test 12 Test 13 Measured average 20 30 40 50 60 70 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 Standardised level difference, DnT, dB Frequency, Hz Prediction - total Measured average

Verification of model at Site A

• 13 wall tests undertaken

at Site A

• Average of measured

tests compared with Bastian prediction

• Sound insulation

underpredicted at low frequency

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Site B Measurements – Rsitu

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• R’ measured for 7 floors, 3

tests disregarded due to notable flanking sound

• Underprediction of sound

insulation at low frequency

20 30 40 50 60 70 80 100 160 250 400 630 1000 1600 2500 Sound reduction index R, R', dB Frequency, Hz Average measured R' Bastian Rsitu Bastian R Insul R

Site B Measurements – 𝐸𝑤,𝑗𝑘,𝑡𝑗𝑢𝑣

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• 𝐸𝑤,𝑗𝑘,𝑡𝑗𝑢𝑣 measured between two pairs of rooms
• Measured values significantly higher than expected

1 2 3 4 5 6 7 8 9 10 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 Direction-averaged velocity level difference, dB Frequency, Hz Measured Bastian

Updated predictions – Site B

• Average of 4 wall tests

compared with predictions

• Use of measured Rsitu

improved the shape of the curve

• Best prediction used

measured Rsitu and 𝐸𝑤,𝑗𝑘,𝑡𝑗𝑢𝑣 from Bastian as input data

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30 40 50 60 70 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 Standardised level difference DnT, dB Frequency, Hz Measured average Prediction - Floor: Bastian, Dv,ij: Bastian Prediction - Floor: Bastian, Dv,ij: Measured Prediction - Floor: Measured, Dv,ij: Bastian Prediction - Floor: Measured, Dv,ij: Measured

Updated predictions – Site B

• Low frequency behaviour

very closely predicted

• Floor flanking dominates

across most of the relevant frequency range

• On-site degradation of wall

performance expected

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30 40 50 60 70 80 100 160 250 400 630 1000 1600 2500 Standardised level difference DnT, dB Frequency, Hz Measured average Prediction - total Prediction - direct-direct Prediction floor-floor

Updated predictions – Site A

• Measured Rsitu corrected for

mass of concrete

• 𝐸𝑤,𝑗𝑘,𝑡𝑗𝑢𝑣 taken from Bastian
• Improved prediction at low

frequency

• Underprediction of sound

insulation at high frequency

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20 30 40 50 60 70 80 100 160 250 400 630 1000 1600 2500 Standardised level difference DnT, dB Frequency, Hz Measured average Prediction - direct-direct Prediction floor-floor Prediction - total Initial Bastian prediction

Conclusions

• More accurate prediction enables more efficient

designs

• Justification for omitting floating floors
• More laboratory floor data required to further

improve predictions

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