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Question Marks on Trees

Frequently Asked Questions

We have gathered several different FAQ:s that might answer any questions you have about calculations in the programs with our databases, do not hesitate to contact us if you can't find an answer to your question!
  • What about changes in the database, in case I would like to trace back?
    Data taken from old versions of the database are stored in each project file (*.BAP). Thus, each calculation is documented with the element data valid at this occasion. Printing the worksheet or exporting to Excel displays all data. In case you still would like to use previous versions of the database, send us a mail. We save all versions distributed from 1999 AC.
  • What can I do in case I miss a construction in the database?
    1. Enter your own data into the database. See the manual, page 169. Basically, go to the Database menue, choose relevant product category and then use right hand click to open a submenue. Either choose NewAsCopy, or NewConstruction. Make sure to use input data for the construction as measured in a laboratory, i.e. without flanking transmission. 2. Contact us. We frequently assess sound insulation of new products for manufacturers and we can certainly help you as well (commissioned work). You can try using Insul, copy and paste, but you should consider the limitations of Insul prior to advising clients on critical constructions using this method (ABK 09 requirement of workmanship). In case you try and use field data, make sure to remove flanking energy before inserting the insulation values, since BASTIAN adds flanking to the model. 3. See below, there are more detailed Q:s on this topic.
  • Is it possible to enter sketches for user defined constructions?
    Yes. Define the image file name in the Database menu and save the file in the Bastian-folder. For constructions in the optional SOAB database, the www addresses of the manufacturers are given. Please look for further information at their pages or contact them.
  • The joint #14 "light-weight wall or slab that connects to a massive partition" looks like it will give strong flanking transmission - is this correct?
    The pictogram may be misinterpreted such that the L-W wall seems to be continous across the junction, thus giving unacceptable flanking transmission. This is (of course) not the case. The massive partition blocks/interrupts the lining. In case the intention of the user is to apply continous lining (e.g. a suspended ceiling in offices), apply junction #15 and give Dn,f data for the flanking element. Refer to the manual (on-line Help, or PDF-file on the BASTIAN CD)
  • How to import field measured data to the BASTIAN database?
    1. If you are certain that your measured data reflect the performance of one single element only, go to the Database menu and open the most relevant category. In the table, right-click and choose NewConstruction. Paste the data and add descriptions of the construction. 2. Be aware of the limitations of field data, i.e. they comprise flanking transmission of connected structures as well as structural loss factors that deviate from laboratory conditions (assumed in BASTIAN). Read reports available under the Learning Center - Papers & Publications or contact us for assistance.
  • Who can use the programs with the databases, is it for acoustical experts only?
    CadnaB, BASTIAN and SONArchitect may be applied to solve various tasks in the building design process. For non-experts, it is safe and simple to calculate sound insulation within a given model of the building, e.g. to change room size, type of flooring, suspended ceiling, wall lining, door, window etc. However, it takes some acoustical experience to make an adequate room model with respect to structural couplings between building elements, taking into account the parameters that influence the power flow between the building elements and the loss factor. Input data of building elements may be adapted to the actual case, e.g. function of light-weight floors that depend on the coupling to the supporting walls. Consulting an expert to refine the calculation model gives high return-on-investment since the constructions may be optimized to meet a given requirement.
  • Can I use light-weight constructions as in EN ISO 12354:2017 ?
    Yes. Just choose the appropriate junctions BEFORE you choose elements. However, for timber joist floors on light weight walls, BASTIAN may underestimate the impact sound caused by flanking transmission. See manual and the FAQ advanced calculation section.
  • What can I do in case I miss a construction in the database?
    Enter your own data into the database. See the manual, page 169. Basically, go to the Database menu (NOT within the ConstructionChooser), choose relevant product category and then use right hand click to open a submenu. Either choose NewAsCopy, or NewConstruction. Make sure to use input data for the construction as measured in a laboratory, i.e. without flanking transmission. How to edit data in SONarchitect will be informed later on. To find appropriate data for an element, get in touch with the manufacturer or contact us. We have special softwares and a large experience in estimating sound insulation of building elements. In case you enter your own data, make sure to state this in the clients report, or whether you apply data from the SOAB database.
  • Are calculations of sound insulation according to EN ISO 12354 consistent with field measurements?
    Answer 1: Yes – on the average, provided the calculation model fits he building constructions in situ. BASTIAN does NOT return "safe" values comp to field measurements, i.e. there are NO hidden margins. Users should apply their own margins, according to local legislations and client's specifications. Answer 2: Estimates of sound insulation in buildings with concrete elements according to the EN ISO 12354 usually agree well on the average when compared to field measurements. After a new set of comparisons in May 2013, the input data of concrete walls were increased by 1 dB 2013-06-01. Such changes are rare, this was after more than 10 years of application of the database. For calculations of timber frames or solid timber, see below. Answer 3: There are some practical aspects you should consider to avoid unnecessary deviations - in both directions. Field measurements can sometimes reveal worse results than expected. This may for instance be caused by measurement errors or poor workmanship. Examples of a few well-known shortcomings: air leakage in unintended gaps and cracks reduce airborne sound insulation; flanking transmission via a continuous outer layer of a facade is easy to forget in the calculation model. Structural bridging reduce insulation of a floating floor, even one single screw in the wrong place transfer energy. Field measurements can also show better results than expected. This may be because you have not customized the calculation model to the actual building. It's not enough to just enter the apartment separating and flanking structures. You should also specify the type of junction of the adjoining structures (e.g. to include structural losses at the junctions of plaster-board back-walls). Go to the Extra, Structural Rev Time and adjust the junction types of all sides of all heavy elements. Typically, this adds 1-1,5 dB. Errors in input data lead to errors in the calculated sound insulation. Consult the suppliers of the products to be used, in order to provide relevant input data. In case you find flaws in the databases, contact us. An example: impact sound reduction from the laboratory can sometimes be hard to achieve in buildings, especially after some years aging of resilient materials under carpets or parquet floors. Apply some margin at high frequencies if deteriorated elasticity may be reasonable to occur. Structural losses must be handled: Input data for concrete elements must be converted since the structural losses in a laboratory (for an element itself) are lower than in the current building, which usually gives an increase of 1-3 dB if all junctions are specified. On the contrary, flanking transmission of adjoining structures to the reception room reduces the insulation. Input data for a single concrete element does not tell much about the sound insulation of a building, it is when you put together all concrete elements ("communicating vessels") that you get an estimate of what the building structure performs. All these aspects are handled by EN ISO 12354. The Swedish building codes BBR and the standards SS 25267/SS 25268 contain rules that say you should fulfill the sound requirement on average within a dwelling or premises, and that single measurements may not deviate by more than 1 or 2 dB. Always make sure to fulfill req's with a calculated value. Remember, it is the rejected measurements, or the risk of getting rejected, which determines the minimal construction being appropriate. As a result, the majority of measurements are likely to meet or even exceed the requirement. This may appear as an over-estimation, but is in many cases necessary. Typically I find 2-3 dB higher sound insulation measured between small rooms than large rooms. Some new test reports show that consultants sometimes only measure between small rooms or only in a favorable direction. The requirement of the standard is clear, test rooms shall be selected to match the building as a whole. In safe designs, sound requirements should be exceeded by 3 dB margin, to obtain reasonable assurance (approximately 90%) to meet the requirements for its field measurement. One or two measurements may still be below the requirement. If no margin is applied, many measurements will still fulfill the requirements but you will get more negative deviations. Only when a large number of measurements is analyzed, these statistical relationships become clear. Large or systematic discrepancies are probably due to the quality of field measurement. Two common reasons for measurement errors are background noise and insufficient spatial averaging (microphone positions did not cover the entire space). What about the EN ISO 12354:2017? Bastian is not yet updated for the new version of the standard, but may still be "tweeked" to handle wooden structures. The uncertainty of calculated sound insulations of timber frame buildings, or building with massive wood (CLT/KL) are currently not known. Timber frame floors are in a separate category. Studded walls on concrete slabs is handled, use the appropriate junction. You may use some temporary data for CLT but be cautious. They are marked with the CA country label, to separate from homogenous concrete. The approach is then to use CLT as with concrete, but with additional layers that perform differently. Use the CA country selector to filter out other data entries than for CLT. 2021-03-18: In the Sept update, there will be 34 CLT constructions added, based on extensive comparisons with lab data. Will be published at BNAM and in Bygg&Teknik in May 2021. Contact me for further details.
  • Are the construction data in the SOAB database the same in CadnaB, BASTIAN, and SONarchitect?
    Yes. Products advertised in the CadnaB and BASTIAN-databases are also distributed to users of SON-architect software, through a cooperation with their Scandinavian distributor Norsonic AS (www.norsonic.no). In case you find differences, those are unintentional, please inform us!
  • Are there standardized outdoor spectra available?
    In the SOAB database, lots of traffic and outdoor noise spectra are included, some harmonized with the new Nordic Calculation Model for the Propagation of Noise (Nord2005). This helps choose the right light-weight walls, outdoor air inlets, windows and renovation glazing have been added (contin. fall 2003). Outdoor levels refer to free field + 3dB, i.e. 2m in front of the façade (unless otherwise is stated in the description). Indoor levels refer to the diffuse field.
  • How to find or change data on elements easily? There are many structures in the database, in particular light weight walls…and still we do not always find what we need in the individual case
    1. BASTIAN displays thumbnail pictures of many constructions, use these rather than browsing all database lines. Or, turn on the diagram display button and look at the sound insulation values, weighted or by 1/3 octaves, to find a construction. Or, choose country selector S for Swedish only, or NT for all Nordic entries. 2. Mark your favourites by making copies: In the Database menu, select your standard choices and make copies of them (right-click, NewAsCopy). Add 3 blank spaces to make them appear at the top. BUT remember to update these copies in case there are changes made to the original data, as announced with update patches from the administrator. 3. The same procedure holds for changes of data, make a copy, rename it and change the data according to your concept
  • How do I calculate with own source room spectra in BASTIAN?
    A) Make sure you have DnTw in the worktable header. If not; change preferences under Extra menu and duplicate the worksheet. Then activate the SubTable in the View menu. You now see the work Source and 3 dots (...) in the bottom line of the worktable. Double-click the dots and choose from the list of available spectra. BASTIAN calculated the A-weighted level in the source room and in the receiver room. If you need to adapt the level, do so under Database menu first, then choose the new spectra in the worktable. If the L1-L2 difference is much larger than anticipated by the DnTw+C value, the spectra of the real source puts less efforts on the partition than assessed by the C-spectrum. B) NB! Sound level refers to diffuse sound level. For outdoor-indoor the level 2 m in front of facade, i.e. the +3 dB position.
  • After having selected the separating element and subsequently the flanking elements the sound reduction for the separating element is changing after each selection. Why?
    As default-configuration the sorting of the flanking paths is set to "Recieving side". This means, that as far as the separating element is concerned, all flanking paths Fd are added to the separating path Dd. This causes the sound reduction index via the separating element to change with each selection of a flanking element. If you select the sorting by junction (Menu Worksheet Sorting) all flanking paths will be added up below the corresponding flanking element leaving the path Dd for the separating element only (see manual). WARNING: Always make complete models, you should see OK at bottom/right corn.
  • When inserting a door into the separating element the weighted sound reduction index in the CONSTRUCTION CHOOSER dialog box differs from the value displayed in the table of the worksheet. Why?
    The value displayed in the table of the worksheet is the sound reduction index referring to the total (gross) area of the separating element. E.g. for a door of S=1,5 m2 inside a separating element with the total area Stot=15m2 the figure displayed in the table is 10*lg(1,5/15)=10 dB larger than the weighted sound reduction index Rw of the door. WARNING: In version 2.3.98, this calculation is erroneous, it refers to the net area. To be corrected in an update.
  • How to import field measured data to the BASTIAN database?
    1. If you are certain that your measured data reflect the performance of one single element only, go to the Database menu and open the most relevant category. In the table, right-click and choose NewConstruction. Paste the data and add descriptions of the construction. 2. Be aware of the limitations of field data, i.e. they comprise flanking transmission of connected structures as well as structural loss factors that deviate from laboratory conditions (assumed in BASTIAN). Read reports available under Learning center - Papers & Publications or contact us for assistance.
  • I have two doors inside the flanking elements. How can I include these doors in the model?
    A) Doors as sound transmitting elements are only considered in case they are situated inside the separating element. Doors or windows inside flanking elements reduce the excited (sending side) or radiating area (recieving side) of the flanking element. This can be considered through the dialog box GEOMETRY DATA (Extras menu). Note, from then, all geometry data are entered manually. B) If the intention is to consider flanking transmission by leakage or direct sound transmission, e.g. via a door-corridor-door path, calculate separately the assembled flanking transmission. Add this value as a fictive flanking element (system) to the database and select it in the calculation table.
  • What can I do in case I miss a construction in the database?
    1. Enter your own data into the database. See the manual, page 169. Basically, go to the Database menue, choose relevant product category and then use right hand click to open a submenue. Either choose NewAsCopy, or NewConstruction. Make sure to use input data for the construction as measured in a laboratory, i.e. without flanking transmission. 2. Contact us. We frequently assess sound insulation of new products for manufacturers and we can certainly help you as well (commissioned work). You can try using Insul, copy and paste, but you should consider the limitations of Insul prior to advising clients on critical constructions using this method (ABK 09 requirement of workmanship). In case you try and use field data, make sure to remove flanking energy before inserting the insulation values, since BASTIAN adds flanking to the model.
  • Is it possible to have different constructions in the source and receiving rooms, e.g. different floors, floorings, ceilings etcetera?
    A1. Yes. First, make sure the type of junctions are correct for the elements you want to apply. Then, d-click in the right column and de-select the Adopt SR-element button to the top-left of the table in the Construction Chooser. You are then free to select any element that matches the selected type of junction, e.g. where there is a mix of heavy and light weight elements. A2. Unfortunately, the junction data cannot be modified under Extra/Junctions. This is due to a change of underlying software (version 2.3.104) used to generate the editable tables.
  • How can I model junctions between plasterboard walls, according to the manufacturers?
    The predefined junctions in BASTIAN refer to solid junctions between solid elements, which is hardly applicable to common junctions between these double walls, at least not in higher sound classes. Until EN ISO 12354-1 has been tested and verified (work in progress, gently, contribute), the user has to choose a junction without attenuation (#15), and then add their own flanking transmission element where the correct junction attenuation is included. Please contribute examples to the SOAB database. However, frequently it turns out this path is not so important, using one of the standard junctions is on the safe side with one exception, timber joist floors on light weight walls, where the ceiling suspension prevents direct transmission but vibration of joists may still excite the wall studs. There are many papers on this issue, have a look under Learning center - Papers & Publications for some.
  • How can a select an insulated lightweight roof as the exterior element for outdoor sound transmission?
    Choose the sloped roof type of calculation sheet. Change the number of exterior elements at the worksheet menu. Change the junction type at all four junctions. Then select the roof and the flanking elements via the CONSTRUCTION CHOOSER dialog box.
  • Measured airborne sound insulation between very large rooms is sometimes less than calculated, but the impact sound agrees. Why so?
    There are at least three reasons for this: 1) junctions/flanking and structural losses must be modelled correctly, see next question. 2) The data for concrete elements were calculated for ordinary sized rooms. In large rooms (>200 m3), modal coupling may decrease R at low frequency somewhat. Look at the German data for concrete, as these indicate what may happen although these data may appear somewhat exaggerated for many practical situations. 3) Air leakage reduce R at medium and high frequency, this must be prevented at ALL junctions. Prescribe PU or Silicone sealing compound to be filled between all dry elements. Concrete fillers must be specially adapted to make up a tight air sealant.
  • I do not find my type of external wall in the database - what can I do ?
    There exist an infinity of external walls and the database cannot comprise all variations. But the simple answer is to choose one of the variety of walls included in the database with a similar build-up, i.e. number of layers on the inside, same type of studs etcetera. Complex skins on the external side often influence the high frequency insulation but not as much the lower parts that are dominated by mass transmission, i.e. they determine mainly the RA,tr. The more complicated solution is to model a new wall in Insul, copy-and-paste to BASTIAN and reduce 3 dB by the +/- 1 dB button next to the spectral figures. Contact us in case you need assistance (commissioned work).
  • Can I use only light weight walls and floors? How are laboratory transmission values translated to in-situ values?
    Yes, BUT with great care. Radiation from light weight load bearing walls is not included in the model. CEN/TC 126/WG 2 works on this item now to find Dvi,j or Kij:s between light-weight junctions. Look at the Vinnova report (SP 2008:16, order at www.sp.se). At InterNoise 2004 (Prague) and Forum Acusticum 2005 (Budapest), some results were presented by Warnock, Quirt and Nightinggale from NRC Canada. Get a new report from http://irc.nrc-cnrc.gc.ca/fulltext/rr/rr168/ (Flanking transmission at the wall/floor junction in multifamily dwellings - quantification and methods of suppression. Research Report 168). This is a complicated matter. At present time there is little practical experience with the algorithm, but the values obtained in BASTIAN with separated sheets in the junctions seem realistic, even slightly conservative. See note 1 below. NOTE 1: Floors resting directly on the studs of light weight walls in the recieving room may cause 5-7 dB higher transmission (i.e. less sound insulation) than the laboratory result of the floor alone, i.e. BASTIAN would return 2-4 dB better insulation than achieved. The advise in SS 25267 annex F is to keep at least 4 dB margin between calculation results (incl. flanking paths) and requirements. Additional structual bridges may increase this difference. If this is expected to resemble the field situation, adjust the floor element data accordingly. Open the database, high-light the floor, righ-click and choose NewAsCopy. Change the title and input data. Always contact the manufacturer of the floor system to get additional information on the influence of flanking transmission in typical building constructions, as determined by measurements. The SBUF data (project 11254) on light-weight floors were taken as lab-data, then reduced by 3 dB for these reasons. Please note that junction data cannot be modified (Extra/Junction), due to a software problem. Contact us in case you need assistance with light weight constructions. NOTE 2: Correction for reduced flanking below the coincidence frequency fc: Check the sigma_free/sigma_forced correction box (ON) for light-weight constructions, in the Preferences section. Why this? The input data of the separating element typically refer to a case where forced transmission dominates and flanking transmission does not contribute significantly. But when the light elements are used in flanking constructions, the direct path is removed and only resonant transmission occurs. Look at Euronoise 2012; papers by Stefan Schoenwald, Jeffrey Mahn and Cathrine Giogou-Carter. Our experience tells that BASTIAN through Heinrich Metzens correction works satisfactory in most cases, compared to Schoenwalds measurements of radiation factors below fc coincidence frequency (around–8 dB).
  • How do I account for the influence of holes and joints in precast heavy hollow core slabs without topping or with thin toppings without reinforcement? What about air leakage?
    The data in the database is already corrected for the influence of joints, cast in an ordinary way. Do not apply forced or restriced border absorption according to the question below, just apply the normal BASTIAN calculation procedure. The results are still within the 3 dB uncertainty interval, this has been tested on a limited number of field measurements. For example, HDF20 330 kg/m2 would be on the limit to pass R'w+C50-3150 52+/-1 dB (class C in SS 25267). Thanks to Spenncon, Aprobo, Strängbetong, Skanska Norge, Bo Gärdhagen and others for their kind support of this investigation. If the HD-elements are parallell to the wall AND the joints between elements are open, i.e. they do not transfer moment, flanking sound insulation may be reduced. This effect is not taken into account in the database (safe approx.). Select junction types as usual. In case the elements are not bonded to each other at the element joints and these are oriented in parallell to the junction, the sound insulation may be greater than calculated. A reason for this is suggested: the hollow core concrete elements do not transmit moment (tension fores) across the joints since there is no reinforcement in the upper part. There will always be small cracks in the element or the topping. However, shear forces do transmit vibrational power to the neighboroughing elements, causing about 3 dB less transmission across joints than estimated. In principle, this applies also to massive precast elements that are jointed without reinforcement. In case more knowledge is gathered on this matter, please tell us. Another problem related to precast slabs, the risk of air leakage in between the elements (not enough grout filling out the gaps). It may not be sufficient to close the V-grout above the wall, all of the joint must be sealed to prevent air leakage.
  • Can I change the areas of windows and doors in BASTIAN?
    Yes. First of all, you may enter several windows of the same type by right-hand click and Insert a new element row. You may repeat this procedure to add more elements. Or, you may copy and modify the data of a window in the database. N.B. Changing the area from the actual area used in the tests may add an error, typically in the order of 3 dB according to EN ISO 140-3. Larger panes tend to decrease the sound insulation. Finding data for a window with a changed area as compared to the actual test calls for a theoretical approach. We can assist you finding such data based on calculations and measurement results. See also EN 14351.
  • Light-weight concrete walls, are there any particular pre-cautions to take ?
    YES - BEWARE !!! Flanking transmission through thin light-weight monolithic structures may cause severe deterioration of sound insulation if they are connected firmly to the slabs in both ends. Walls, also inner walls, made by l-w concrete, aerated concrete and similar materials with fc in the mid frequency region must NOT be attached firmly to the upper slab. See ph.d. thesis by Kihlman (Chalmers 1960), available at www.isac.cc. This may now be illustrated in BASTIAN with new element data (no 202 and 203 b-e). In the preference settings, Option tab, activate limits for alpha by the default button (0,050,5). In practice, always use a soft joint to the upper slab, e.g. with mineral wool and a plastic seal to prevent problems. Also avoid firm connections between building service equipment and such walls. To hide pipes in these walls used to be considered a very practical solution, BEWARE... The flanking problem was explained by Tor Kihlman, where the poor R around fc caused both excitation of the wall in the S-room, as well as radiation in the R-room. The bending waves in the wall may cause in-plane waves in the slab concrete floor, which would reduces the junction attenuation compared to the EN ISO 12354-1 value (~high mass ratios). Another transmission may be caused by longitudinal wave resonances in the l-w wall, causing excessive transmission through several joints/floors. The soft joint blocks all of these transmissions, also from various impact sounds (doors, kitchen lockers, WC), but the l-w walls must be completely separated by the soft joints. Take care to insulate any stability reinforcements with rubber pads and prevent any pipes to run through the joints.
  • The calculated sound insulation of concrete structures sometimes appears to be too HIGH. Why ?
    The structural loss factor may in some cases be OVERESTIMATED by the default setting "Maximum coupling". A recent example: A corner room with light weight facade elements on three sides. The default setting will assume a continous slab, although the border of the slab may be considered reflective. Change to User defined SRT and define the types of junction of all connecting elements (4 borders face each element). In practice, this means that second order transmission paths are taken into account with respect to structural loss factor, but they are not used to estimate second order flanking transmission (as follows from the theoretical model in EN ISO 12354). Use the Worksheet menu, Export option to view all details in Excel. Typically, the structural rev. time correction (the "diagram button") is in the range (-2, -4 dB) when several of the borders of the slab do not transmit energy to the surrounding structures. Tell us if you have another experience on this matter. See question "area factor".
  • Is the "area factor" according to EN ISO 12354 taken into account, i.e. does BASTIAN correct properly for the increased loss factor due to flanking transmission through connected large heavy structures when only light-weight walls define the rooms ?
    Yes & No. BASTIAN does increase the loss factor, but unfortunately not enough if the slab is continous and very large (homogenous concrete) (v 2.3). In case of large heavy walls or slabs with only light weight walls that encloses a much smaller area, e.g. in an office or in a hospital, the vibrational power flow may direct away from the recieving room. The sound insulation horisontally will be underestimated (-1.5,-3 dB) by BASTIAN v 2.3 in extreme cases. For hollow core concrete slabs with a thin topping, the following advice is not applicable unless the joints are bonded in a special way or there is a thick reinforced topping, see question above. We suggest the use of a practical compromise, as supported by measurement results from the field (*). The loss factor of continous concrete slabs or walls may be increased by the user to get more accurate results. More measurement results would be needed to confirm this way of handling the "area effect" (please contribute!). In the Extras/Structure Reverberation time, first choose Max Coupling. Then choose UserDefined Coupling. Then change fc of each of the connected slabs to 500 Hz along one of its borders, preferably the one at the common junction. This will add 1.5-3 dB horisontally and 0.5-1.0 dB vertically. Use this correction with when YOUR experience tells that the losses at the borders are high, e.g. when the heavy partition wall or slab is much larger (as limited by supporting heavy structures) than the sending or recieving room. Typically, the structural rev. time correction (look at the Diagram) will be in the range (-5, -7 dB) when 3 or 4 of the borders of the slab do transmit energy efficiently to the surrounding structures. (*) Comparison with 7 measured cases in Norway and Sweden (*) have been used to define this procedure. Thanks to contributions from Delta Akustik&Vibration, Brekke&Strand, Sinus, Ingemanssons, WSP and others! NOTE: This does not apply to light weight floorings and sub-floors that are continous under the walls. See paper by Quirt (NRC Canada) at InterNoise 2004.
  • What safety margin is needed, i.e. what is the confidence in a calculated value using BASTIAN?
    There is certainly no general answer to this question that covers all aspects. But before going into long discussions, we recommend all users to keep a margin of at least 3 dB to a required value in an individual case. If some averaging of several cases is allowed, or there is some practical experience with the calculation model for the element used, it may be appropriate to reduce the margin to (say) 1-2 dB. When the main transmission occurs through light weight constructions, such as a timber joist floor, 4 dB seem more appropriate. Some reasons for discrepancies between calculated and measured results are discussed in the body text of the standard (EN ISO 12354). In the NORDTEST tech report 603, a comparison between about 40 field results and calculations support this recommendations. The data for light-weight floors labelled SBUF xxx have already been reduced by 3 dB, so the 3 dB margin on the overall result should be on the safe side (no guarantees though!).
  • Are calculations of sound insulation according to EN ISO 12354 consistent with field measurements?
    Answer 1: Yes – on the average, provided the calculation model fits he building constructions in situ. BASTIAN does NOT return "safe" values comp to field measurements, i.e. there are NO hidden margins. Users should apply their own margins, according to local legislations and client's specifications. Answer 2: Estimates of sound insulation in buildings with concrete elements according to the EN ISO 12354 usually agree well on the average when compared to field measurements. After a new set of comparisons in May 2013, the input data of concrete walls were increased by 1 dB 2013-06-01. Such changes are rare, this was after more than 10 years of application of the database. For calculations of timber frames or solid timber, see below. Answer 3: There are some practical aspects you should consider to avoid unnecessary deviations - in both directions. Field measurements can sometimes reveal worse results than expected. This may for instance be caused by measurement errors or poor workmanship. Examples of a few well-known shortcomings: air leakage in unintended gaps and cracks reduce airborne sound insulation; flanking transmission via a continuous outer layer of a facade is easy to forget in the calculation model. Structural bridging reduce insulation of a floating floor, even one single screw in the wrong place transfer energy. Field measurements can also show better results than expected. This may be because you have not customized the calculation model to the actual building. It's not enough to just enter the apartment separating and flanking structures. You should also specify the type of junction of the adjoining structures (e.g. to include structural losses at the junctions of plaster-board back-walls). Go to the Extra, Structural Rev Time and adjust the junction types of all sides of all heavy elements. Typically, this adds 1-1,5 dB. Errors in input data lead to errors in the calculated sound insulation. Consult the suppliers of the products to be used, in order to provide relevant input data. In case you find flaws in the databases, contact us. An example: impact sound reduction from the laboratory can sometimes be hard to achieve in buildings, especially after some years aging of resilient materials under carpets or parquet floors. Apply some margin at high frequencies if deteriorated elasticity may be reasonable to occur. Structural losses must be handled: Input data for concrete elements must be converted since the structural losses in a laboratory (for an element itself) are lower than in the current building, which usually gives an increase of 1-3 dB if all junctions are specified. On the contrary, flanking transmission of adjoining structures to the reception room reduces the insulation. Input data for a single concrete element does not tell much about the sound insulation of a building, it is when you put together all concrete elements ("communicating vessels") that you get an estimate of what the building structure performs. All these aspects are handled by EN ISO 12354. The Swedish building codes BBR and the standards SS 25267/SS 25268 contain rules that say you should fulfill the sound requirement on average within a dwelling or premises, and that single measurements may not deviate by more than 1 or 2 dB. Always make sure to fulfill req's with a calculated value. Remember, it is the rejected measurements, or the risk of getting rejected, which determines the minimal construction being appropriate. As a result, the majority of measurements are likely to meet or even exceed the requirement. This may appear as an over-estimation, but is in many cases necessary. Typically I find 2-3 dB higher sound insulation measured between small rooms than large rooms. Some new test reports show that consultants sometimes only measure between small rooms or only in a favorable direction. The requirement of the standard is clear, test rooms shall be selected to match the building as a whole. In safe designs, sound requirements should be exceeded by 3 dB margin, to obtain reasonable assurance (approximately 90%) to meet the requirements for its field measurement. One or two measurements may still be below the requirement. If no margin is applied, many measurements will still fulfill the requirements but you will get more negative deviations. Only when a large number of measurements is analyzed, these statistical relationships become clear. Large or systematic discrepancies are probably due to the quality of field measurement. Two common reasons for measurement errors are background noise and insufficient spatial averaging (microphone positions did not cover the entire space). What about the EN ISO 12354:2017? Bastian is not yet updated for the new version of the standard, but may still be "tweeked" to handle wooden structures. The uncertainty of calculated sound insulations of timber frame buildings, or building with massive wood (CLT/KL) are currently not known. Timber frame floors are in a separate category. Studded walls on concrete slabs is handled, use the appropriate junction. You may use some temporary data for CLT but be cautious. They are marked with the CA country label, to separate from homogenous concrete. The approach is then to use CLT as with concrete, but with additional layers that perform differently. Use the CA country selector to filter out other data entries than for CLT.
  • Row houses, detached by a common thin (10 cm) concrete slab casted on EPS or min-wool heat insulation: The calculated sound insulation appears to be too low, compared to experience. Why ?
    Measurements suggest that the loss factor of the plate is much higher than expected just from border absorption of the plates. We suggest that you either a) quick-fix, just insert a +20% thicker slab or b) force one border absorption factor to 0,5 to coop with this. In v 2.3 choose the Extra menu, Struct. Rev. Menu, change fc of each of the borders to 500 Hz. You may also change border absorption in Extras menu. Typically, a 3-4 dB higher insulation should be the result. If more knowledge is gathered on this point, tell us. The effect of a local increase of thickness is still under debate, I think it is not contributing any vibration isolation of the slab. Remains to be tested...
  • How do I account for the direction of holes in precast heavy hollow slabs in a junction with massive wall elements (perpendicular/parallell to the junction)?
    The holes themselves do not influence the sound insulation but of course they ease the weight of the slab. The important thing is the joint. If the elements are parallell to a wall AND the joints between the elements are made in the ordinary way (i.e. they do not transfer moments at high frequencies), flanking sound transmission may be decreased, i.e. the real sound insulation will be higher than calculated. This effect is not taken into account in the database (i.e., a safe approximation). Select junction type according to the above advise. See next question as well. In case more knowledge is gathered on this matter, please tell us.
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