säker på osäkerhet i byggakustik · 2019. 8. 19. · simmons akustik & utveckling ... 0,2 s in...

NAS årsmöteTrondheim

2013-10-25

Christian Simmons

Säker på Osäkerhet i Byggakustik

Simmons akustik & utveckling ab, Chalmers Teknikpark, SE-412 88 GöteborgTelefon/Mobil: +46 (0) 31 27 66 00 [email protected] www.simmons.se

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Säker på OsäkerhetNAS Trondheim 25 okt 2013Christian Simmons

Simmons akustik & utveckling

Expectations !

• High demands for soundinsulation

• Lifestyle, expectations• Need for quitness

• Costs vs. Performance

• Safety margins based onstatistical considerations

NAS Årsmöte 2013-10-25 Trondheim Säker på Osäkerhet


Sound requirements for residential houses are based on performance (dimensions). Unique designs…difficult…



Who takes the responsibility for the sound properties of the building?



The EN 12354 standards convert element data into buildingperformance requirements

NS 8175


ISO 16283


Safety: Which element data are reliable?3 types of data source may be considered:

• A. “Laboratory measurements” –they only reflect the real performance of- 1 sample product in- 1 sample laboratory- under idealized circumstances- are feasible for small elements (windows, doors, air inlets etc)

• To be useful (reliable) for complexelements, there must be- a series of tests,- under non-idealized conditions,- performed in several laboratories

• At least, apply margins from round robintests of reproducibilities



New products – laboratory data variations



Missing data for old or generic constructions: ”tune” calculated input data to the best fit

1. Take lab data of similarconstructions, (2-3 labs)

2. Calculate the sound insulationfor each case

3. Compare calc-lab data4. Average & Std Dev

empirical correction5. Calculate the real

constructions and add thesecorrections

6. Compare to field data



Luleå-bjälklaget (timber joist floors constructed in situ)

Results from 170 field measurements in similar 2-storey houses, floating floor & susp. ceiling….BASTIAN database has 3 series of timber floors meas in lab, 3 dB ”penalty” added

170 timber floors

2025303540455055606570

Ii dB

100H

z

125H

z

160H

z

200H

z

250H

z

315H

z

400H

z

500H

z

630H

z

800H

z

1kH

z

1.25

kHz

1.6k

Hz

2kH

z

2.5k

Hz

3.15

kHz

dB



Room acoustics affect quality of life (not just a comfort aspect)

BBR 2006 - Boverkets handbok Ljuddagen 2008 : 2007221 / 2008-11-20 © 2008 S.A.U.NAS Årsmöte 2013-10-25 Trondheim Säker på Osäkerhet


Sound absorption, round robin



…so, are there better sources of input data for walls, floors?

• B. “Field measurements” (in situ, in the building or in the field) –– performance of an assembly of elements, under realistic but unknown

circumstances– the Robust Details system in the UK quires 30 field measurements to

document a ”construction”, i.e. an element– Large random errors but small systematic errors, i.e. chaotic data sets

result from field data if they are not ”normalized” to reflect performance of the element only

• C. “Theoretical calculations” –– estimates the performance of an element with assumed properties,

its accuracy being limited by the theoretical model and underlyingassumptions

– logical, structured data follows (low random error, possibly high systematicerror)

– Suitable for old, generic constructions (without manufacturers support)



Learn from field meas’sonly – is not practical

• 4 buildings of ”same”construction:

• Airborne insulationof HC floor + parquet

• Different consultantsmade the measurements

• Floor direct transmissiondominated

• Good agreementwith calculations on theaverage, but individualvariations because ofunforeseen effects ofworkmanship and measerrors



…so, are there better sources of input data for walls, floors?

• B. “Field measurements” (in situ, in the building or in the field) –– performance of an assembly of elements, under realistic but unknown

circumstances– the Robust Details system in the UK quires 30 field measurements to

document a ”construction”, i.e. an element– Large random errors but small systematic errors, i.e. chaotic data sets

result from field data if they are not ”normalized” to reflect performance of the element only

• C. “Theoretical calculations” –– estimates the performance of an element with assumed properties,

its accuracy being limited by the theoretical model and underlyingassumptions

– logical, structured data follows (low random error, possibly high systematicerror)

– Suitable for old, generic constructions (without manufacturers support)



Use exact tools? FEM-tools validated vs analytical methods



Vibration reduction at junctions by FEM analyses


Simmons akustik & utvecklingNAS Årsmöte 2013-10-25 Trondheim Säker på Osäkerhet


Different boundary conditions, but…



Which model for thevibration reduction index ?



Ex 1: with random differences only between the calculated – measured sound insulation



Ex 2: systematic and random differencescalculated – measured sound insulation

Needtoincreasemarginby1dB



Student’s t-distr, k-factorssingle sided conf.interval

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Uncertainty of field measurements (only)

• Situation B in ISO/WD 140-2:2009, (c.f. ISO/FDIS 12999-1:2013)– same test objects and test rooms, but– different operators, routines and equipments

• aimed to test reproducibility of measurement methods under field conditions(rather than the properties of a test object)



Differences calculated – measured insulations

• Field cases collected (not perfectly documentedassumptions)• Both random and systematic influences discussed …• Results appear reasonably like other authors results…more data

3 dB margin – EN 12354 is acceptable (heavy floors)NAS Årsmöte 2013-10-25 Trondheim Säker på Osäkerhet


Reverberation timesin classrooms

• 44 classrooms, calc’s compared to field meas’s

• 23 ”simple” rooms, i.e. diffusingfurnitures etc.

• 0,2/0,1 s agreed tolerances



Uncertainty budget helps focus improvements

• Ruff/Fischer, Hall and others..measured Ri, Rj, Kij and η• Example from Wittstock, uncertainty of each parameter estimated & added to

global uncertainty of a calculation



Design goals & tolerances:– uncertainties ”built-in” the SS 25267/68

• Results of field measurements must meet each type of requirement on the average within each dwelling.

• The maximum unfavourable deviations from the requirements– 1 dB for the single weighted numbers of sound reduction (ISO 717, 100-3150

Hz)

– 2 dB when spectrum adaptation terms for low frequencies (50-3150 Hz) are included

– 2 dB for service equipment sound pressure levels in third octave bands 31-200 Hz.

– 0,1 second for the reverberation time in octave bands 250-4000 Hz,0,2 s in the 125 Hz octave band



A procedure to find input data & margins that suit consultants: compare calculations with field data, systematically



I analyzed impact data of 40 well documented field cases



Idea: combine all sources !



New methods for sound pressure level measurements at lowfrequencies



Systematic deviations from true room average



Random deviations 24 measurement methods



prEN ISO 16283-1


prEN ISO 16283-1 test in a furnished living room 25 m2


Practical considerations

• Some practical problems with moving microphonetechniques (manual scanning) emerged during the measurements.

• It is difficult to fit wide circles of various shapes intothe narrow spaces typical for small and denselyfurnished rooms.

• If parts of the microphone path come close, the result approximates one single fixed position taken in this part of the room and obtains an unknownweigt in the average.

• The manual moving microphone methods weresomewhat prone to causing noise from body and clothes, which may cause errors in the receivingroom if the loudspeaker sound level is not highenough.

• The fixed positions method was easier to performthan anticipated, where the operator may payattention to the data acqusition, S/N etc instead offocus on the mic movement



Applied Acoustics: Correlation between sound insulation and occupants’ perception– Proposal of alternative single number rating of impact sound Fredrik Ljunggren1 Christian Simmons2 Klas Hagberg3

Questionnaire vs Measurements

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Structure borne sounds



Structure borne sound from service equipment-substitution method (force sources) – round robin

Unbalanceweight 1,5 kgYnormal Ylow Yhigh

Need to make complementary analyses, e.g. pointmobilites of source and floor, statistics of each machine case etc…



Average – 1 StdDev

Test object – TM vibration level difference, dB


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