Environmental Noise Report · MCU13/0064

3.2 Mechanical Plant & Equipment Noise Criteria

3.2.1 Background Plus

The ‘Background Plus’ noise limits are widely accepted in Queensland as being appropriate noise
limits for minimising the risk of noise complaints. ‘Background Plus’ noise limits are regularly used
by DERM when specifying noise criteria or assessing noise complaints. Traditionally ‘background
plus’ criteria have been applied as presented in Table 3.1.

                                    Table 3.1: Informal ‘Background Plus’ Noise Criteria
Noise Sensitive Place
Daytime 7am - 6pm                                                LAmax,adj ≤ Background noise level plus 5 dB(A)
Evening 6pm - 10pm                                               LAmax,adj ≤ Background noise level plus 5 dB(A)
Nighttime 10pm - 7am                                             LAmax,adj ≤ Background noise level plus 3 dB(A)
Noise Sensitive Commercial Place
Daytime 7am - 6pm                                                LAmax,adj ≤ Background noise level plus 10 dB(A)
Evening 6pm - 10pm                                               LAmax,adj ≤ Background noise level plus 10 dB(A)
Nighttime 10pm - 7am                                             LAmax,adj ≤ Background noise level plus 8 dB(A)
Note: Background noise level is defined as LAbg,T.


These limits are based on superseded AS 1055.2:1989 ‘Acoustics-Description and measurement of
environmental noise Part 2: Application to specific situations’ reference:

           Where LAmax,adj,T is greater than LAbg,T, the noise is likely to be discernible and if the difference
           is substantial enough the noise will be annoying.

It should be noted that AS 1055.2:1989 also states the following:

           Difference of 5 dB or less may be of marginal significance with respect to annoyance.

AS 1055.1:1989 ‘Acoustics-Description and measurement of environmental noise Part 1: General
Principles‘ states that:

           LA90,T is commonly taken to be an approximation of LAbg,T

           LA10,T is commonly taken to be an approximation of LAmax,T

With adoption of the Environmental Protection (Noise) Policy 2008, Reprint 1A, 2012 ‘background
plus’ criteria have been changed from those used informally. Environmental Protection (Noise)
Policy 2008 adopts the following ‘background plus’ criteria to control background creep:

     (b) for noise that varies over time measured by LAeq,adj,T—more than 5dB(A) greater than the
        existing acoustic environment measured by L A90,T.

The latest ‘background plus’ noise criteria as defined in the Environmental Protection (Noise) Policy
2008 have been used to assess potential annoyance from industry located to the southeast of the
proposed site. A minimum background of 30 dB(A) is applied where measurements of existing
background as present in Table 2.2 are below this level. The use of an LAeq descriptor allows for the


0023-R1-01 KHA Makepeace Island Noise Impact Assessment Report                                                      8
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