Acoustic design guide - Caice

Acoustic DesignGuideNR and NC CurvesCIBSE Noise RatingsEnvironmental Noise ControlMaximum Air Velocities in DuctsPrivacy in Cellular Offices14th February 2012

ContentsNoise CurvesNR Curves and Table 1NC Curves and Table 2CIBSE Noise Ratings 3Environmental Noise Control 4Maximum Air Velocities in Ducts 5Privacy in Cellular OfficesA Background to Privacy 6Medium privacy in cellular offices 7High privacy in cellular offices 9iwww.caice.co.ukCAICE Acoustic Design Guide

NR Curves and Tablewww.caice.co.ukCAICE Acoustic Design Guide1

NC Curves and Table2www.caice.co.ukCAICE Acoustic Design Guide

CIBSE Noise Ratingswww.caice.co.ukCAICE Acoustic Design Guide3

Environmental Noise Control4www.caice.co.ukCAICE Acoustic Design Guide

Maximum Air Velocities in Ductswww.caice.co.ukCAICE Acoustic Design Guide5

Privacy in Cellular OfficesA Background to PrivacyWhat is privacy?The isolation of normal or raised speech produced in one roomfrom possible listeners in another room.Speech levelsThe index values shown in the table assume normal speechnoise levels. Add 6dB if the criteria are to be achieved based onraised speech.What main factors determine privacy?1. The voice level of the person speaking within the sourceroom.2. The background noise level within the receiving room.Selecting a suitable building structureThe table below shows a range of average room-to-room noisereductions for different types of building structure.3. The noise reduction of the building structure between therooms.Selecting an appropriate privacy criterion or ratingThe table below shows privacy criteria in terms of speechintelligibility, with a corresponding privacy rating. The indexvalues shown are calculated by adding the required NoiseRating (NR) level within the receiving room to the average dBnoise reduction of the building structure between the two rooms.Building Structure Between RoomsBudget demountable partitioning and suspendedceilingQuality demountable partitioning and suspendedceilingFull height standard studded plasterboard partitioningFull height jumbo studded plasterboard partitioningFull height single leaf dense block wallAverage NoiseReductionBelow 35 dB35 to 40 dB40 to 50 dB50 to 55 dB50 to 55 dBPrivacy Criteria Privacy Rating IndexIntelligible Low Below 75dBEliminating noise flanking pathsBetween intelligible and unintelligible Medium 75 to 80 dBUnintelligible High 80 to 90 dBInaudible Very High Above 90 dBNoise reduction performance of structures will be undermined,unless noise flanking paths, such as those listed below, areeliminated.Doors and door sealsGlazed sections within demountable partitioningFor example to achieve a high privacy rating when the receivingroom background noise level is NR40, the building structuremust provide an average noise reduction of between 40 and50dB.Demountable partition joint to the suspended ceilingApertures in the suspended ceiling, such as grilles, etc6www.caice.co.ukCAICE Acoustic Design Guide

Privacy in Cellular OfficesMedium privacy in cellular officesMedium privacy is normally acceptable for cellular offices, andtwo methods for achieving this are shown, based on the following:Demountable partitioning systemSuspended ceiling systemVoid mounted fan coil units (omitted from drawings forclarity)Before selecting one of these methods the following factorsshould be considered:Will the office layout change or is it fixed?Is it a new or existing building?How many cellular offices are there?Which method would be easier to install?Return air ceiling voidWhich would be most cost effective? Background noise level of NR35 to 40Method 1 - Cellular offices with maximum flexibilityand medium privacyReturn air ceiling voidIdeal for new build if office layouts may changePartitions can be moved without affecting privacyReturn air grillesfitted withHG acoustic hoodsHG acoustic hoods protect all ceiling aperturesHigh quality suspendedceiling systemNR35 to 40 cellular officeReturn air ceiling void remains clearSimple installation makes privacy easy to achieveHigh quality demountablepartitioning systemThis method utilises HG acoustic hoods, which are detailed inthe CAICE Acoustic Hood data sheet. In addition high qualitydemountable partitioning and suspended ceiling systems areincorporated throughout the office.Hoods should be fitted to the rear of all ceiling penetrations,such as return air grilles, diffusers or luminaires, to ensure thatthe acoustic integrity of the ceiling system is maintained.The major benefit of this method is that the demountable partitionscan be moved to modify the size and position of the cellularoffices, without affecting privacy.To achieve medium privacy a 40dB (R’w) partition system anda 40dB (Dncw) ceiling system should be used as a minimum.www.caice.co.ukCAICE Acoustic Design Guide7

Privacy in Cellular OfficesMethod 2 - Cellular offices with medium privacy andlimited flexibilityReturn air ceiling voidAcoustic void barrierReturn air crosstalk attenuatorIdeal for existing offices where layout is fixedReturn air grillesAcoustic void barriers required above partitionsExisting partitions and ceiling may be retainedBudget suspendedceiling systemNR35 to 40 cellular officeCrosstalk attenuators protect return air pathVoid barrier enables budget ceiling to be usedHigh quality demountablepartitioning systemThis method utilises acoustic void barriers, penetrated by returnair crosstalk attenuators. Although high quality partitioning is stillrequired, a budget ceiling system can be used, as noise betweenadjacent rooms has to pass through the ceiling and thevoid barrier.This method is ideal where the office layout is fixed, or whereonly a few cellular offices are located within a large office area.However it may not be suitable for new buildings with many cellularoffices, where the layouts are subject to change.This is because the void barriers must be moved in conjunctionwith the partitions.To achieve medium privacy a 40dB (R’w) partition system, a32dB (Dncw) ceiling system, and a 35dB (R’w) void barriershoud be used.Typically the return air crosstalk attenuator should be 900mmlong, with an average insertion loss of 30dB between 500 and4000Hz.8www.caice.co.ukCAICE Acoustic Design Guide

Privacy in Cellular OfficesHigh Privacy in Cellular OfficesHigh privacy would only normally be required for cellular officesif they were being used for sensitive or confidential discussions.For example a conference room, a board room, an interviewroom, etc, may all need a higher degree of privacy, but it is difficultto achieve this with demountable partitioning systems.This method is therefore based on cellular offices with full heightstudded plasterboard partitioning, which should achieve 50dB(R’w).However because the partitioning is fixed, there is limited flexibilityto subsequently change the office layouts.Cellular Offices with high privacy but limited flexibilityLayout of cellular offices is fixedReturn air ceiling voidReturn air crosstalk attenuatorPlasterboard partition must be full heightReturn air grillesCrosstalk attenuators protect return air pathPartition enables budget ceiling to be usedSuspendedceiling systemNR35 to 40 cellular officeFull height fixed studdedplasterboard partitioningCeiling acoustic performance is not critical, as the noise reductionbetween rooms is provided by the full height partition. Typicallythe return air crosstalk attenuator should be 1200mm long,with an average insertion loss of 40dB between 500 and4000Hz..Details on rectangular and circular attenuators suitable for crosstalkapplications can be found in the CAICE Attenuator Brochure.www.caice.co.ukCAICE Acoustic Design Guide9

Telephone0118 918 6470Facsimile0118 918 6480enquiries@caice.co.ukwww.caice.co.ukCAICE Acoustic Air Movement Ltd.Riverside House3 Winnersh FieldsGazelle CloseWinnershWokinghamRG41 5QS