MCU19-0132 Applicant's Response - Att 3 Acoustic

FACT SHEET
             Effect of Fixing Plasterboard
             Whilst a 150 thick precast concrete panel
             has a Ctr value of -5, this value is made
             more negative if a plasterboard wall on
             furring channels is fixed to the precast
             wall, giving a less favourable result
             overall. The thinner the furring channel
             and the lighter the plasterboard, the
             more the Ctr factor is made negative.
             This should be watched carefully. When
             dealing with internal noise and furring
             channels are applied to both sides of
             the precast wall together with the use
             of 10mm plasterboard the effect of the
             two cladding systems is compounded
             in respect to Ctr. If it is necessary to
             provide cladding with airspace for the
             running of services then it is important
             that the plasterboard is either 16mm
             or 13mm sound rated, that the furring
             channels are no less than 28mm deep
             and that effective insulation is applied to
             both cavities.

             It can be seen from Table 1 that a 150
             mm precast concrete panel (which
             weighs 360 kg/m2) would provide at
             least 50 dB reduction of sound levels
             from outside to inside when exposed
             to road or rail traffic (or factory noise –
             refer to the Handbook for more detailed
             information).

             Another simple rule of thumb that can
             be applied to materials to calculate their
             approximate transmission loss is the
             ‘mass law’ equation:

             TL = 20 log 10 (mf) – B
             Where: TL = transmission loss (dB)
             m = surface mass (kg/m2)
             f = frequency (Hz)
             B = 48 dB (on average but can range
             from 45-53).



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