Säker på Osäkerhet i Byggakustik. f e s. NAS årsmöte Trondheim Christian Simmons

Transkript

1 Säker på Osäkerhet i Byggakustik NAS årsmöte Trondheim Christian Simmons f e s ab, Chalmers Teknikpark, SE Göteborg Telefon/Mobil: +46 (0) info@simmons.se

2 Säker på Osäkerhet NAS Trondheim 25 okt 2013 Christian Simmons

3 Expectations! High demands for sound insulation Lifestyle, expectations Need for quitness Costs vs. Performance Safety margins based on statistical considerations

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

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

6 The EN standards convert element data into building performance requirements NS 8175 ISO 16283

7 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 complex elements, there must be - a series of tests, - under non-idealized conditions, - performed in several laboratories At least, apply margins from round robin tests of reproducibilities

8 New products laboratory data variations

9 Missing data for old or generic constructions: tune calculated input data to the best fit 1. Take lab data of similar constructions, (2-3 labs) 2. Calculate the sound insulation for each case 3. Compare calc-lab data 4. Average & Std Dev empirical correction 5. Calculate the real constructions and add these corrections 6. Compare to field data

10 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 db Ii db 100Hz 125Hz 160Hz 200Hz 250Hz 315Hz 400Hz 500Hz 630Hz 800Hz 1kHz 1.25kHz 1.6kHz 2kHz 2.5kHz 3.15kHz

11 Room acoustics affect quality of life (not just a comfort aspect) BBR Boverkets handbok Ljuddagen 2008 : / S.A.U.

12 Sound absorption, round robin

13 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 underlying assumptions logical, structured data follows (low random error, possibly high systematic error) Suitable for old, generic constructions (without manufacturers support)

14 Learn from field meas s only is not practical 4 buildings of same construction: Airborne insulation of HC floor + parquet Different consultants made the measurements Floor direct transmission dominated Good agreement with calculations on the average, but individual variations because of unforeseen effects of workmanship and meas errors

15 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 underlying assumptions logical, structured data follows (low random error, possibly high systematic error) Suitable for old, generic constructions (without manufacturers support)

16 Use exact tools? FEM-tools validated vs analytical methods

17 Vibration reduction at junctions by FEM analyses

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19 Different boundary conditions, but

20 Which model for the vibration reduction index?

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

22 Ex 2: systematic and random differences calculated measured sound insulation Need to increase margin by 1 db

23 Student s t-distr, k-factors single sided conf.interval Si m mo ns 23

24 Uncertainty of field measurements (only) Situation B in ISO/WD 140-2:2009, (c.f. ISO/FDIS :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)

25 Differences calculated measured insulations Field cases collected (not perfectly documented assumptions) Both random and systematic influences discussed Results appear reasonably like other authors results more data 3 db margin EN is acceptable (heavy floors)

26 Reverberation times in classrooms 44 classrooms, calc s compared to field meas s 23 simple rooms, i.e. diffusing furnitures etc. 0,2/0,1 s agreed tolerances

27 Uncertainty budget helps focus improvements Ruff/Fischer, Hall and others..measured R i, R j, K ij and η Example from Wittstock, uncertainty of each parameter estimated & added to global uncertainty of a calculation

28 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 1dB for the single weighted numbers of sound reduction (ISO 717, Hz) 2dB when spectrum adaptation terms for low frequencies ( Hz) are included 2dB for service equipment sound pressure levels in third octave bands Hz. 0,1 second for the reverberation time in octave bands Hz, 0,2 s in the 125 Hz octave band

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

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31 I analyzed impact data of 40 well documented field cases

32 Idea: combine all sources!

33 New methods for sound pressure level measurements at low frequencies

34 Systematic deviations from true room average

35 Random deviations 24 measurement methods

36 pren ISO

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38 pren ISO test in a furnished living room 25 m 2

39 pren ISO test in a furnished living room 25 m 2

40 Practical considerations Some practical problems with moving microphone techniques (manual scanning) emerged during the measurements. It is difficult to fit wide circles of various shapes into the narrow spaces typical for small and densely furnished 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 unknown weigt in the average. The manual moving microphone methods were somewhat prone to causing noise from body and clothes, which may cause errors in the receiving room if the loudspeaker sound level is not high enough. The fixed positions method was easier to perform than anticipated, where the operator may pay attention to the data acqusition, S/N etc instead of focus on the mic movement

41 Questionnaire vs Measurements 8 Annoyance - Impact Sound Lnw+CI,AkuLite, Applied Acoustics: Correlation between sound insulation and occupants perception Proposal of alternative single number rating of impact sound Fredrik Ljunggren 1 Christian Simmons 2 Klas Hagberg 3

42 Structure borne sounds En

43 Structure borne sound from service equipmentsubstitution method (force sources) round robin Need to make complementary analyses, e.g. point mobilites of source and floor, statistics of each machine case etc Y normal Y low Y high Unbalance weight 1,5 kg

44 Average 1 StdDev Test object TM vibration level difference, db