sydney-city-centre-review-of-environmental-factors

6.2.2 Assessment criteria
Noise averaging periods
Noise can be measured over various periods of time. The five ‘averaging periods’
used in this REF are described below:
L Aeq describes the average noise levels across a period of time (either day,
evening or night, or over a 15-minute period)
L A90 describes the average noise levels that occur for 90 per cent of the time so
as to remove any outlying high noise levels. L A90 is used to describe the
background noise level
L A10 describes the average noise levels that occur for 10 per cent of the time,
therefore describing the nosiest periods
L Amax describes the average maximum noise level recorded at any point in time
Rating background (noise) levels (RBLs) described the ambient noise levels
during the day, evening and at night. It represents the overall single-figure
background noise level determined based on measured L A90 in each relevant
assessment period as described in detail in the INP (EPA 2000).
Construction noise assessment criteria
The ICNG establishes construction NMLs for a number of sensitive receiver-types.
Reasonable and feasible safeguards and management measures should be
implemented where NMLs are exceeded either during or outside of recommended
standard hours for construction work. The standard hours cover: Monday–Friday
7.00am–6.00pm and Saturday 8.00am–1.00pm. They represent the times of the day
when receivers are likely to be less sensitive to noise impacts. Consequently, during
the recommended standard hours for construction the NMLs for residential receivers
are less stringent (ie higher). For all other receiver-types the NMLs are not timedependent.
Residential receivers
For residential receivers, two NMLs are established under the ICNG. The first
represent noise limits above which the receiver is considered likely to be affected by
noise impacts (termed ‘noise affected’). This is derived from the determined RBL plus
an additional permissible level of construction noise. The second, more stringent,
NML is an absolute limit above which there is anticipated to be notable affects
(termed ‘highly noise affected’). Table 6-13 shows the management levels for
construction noise on residential receivers and how they are applied to the proposal
during standard and non-standard construction hours (termed ‘out of hours’ work). As
noted above, due to the density of residential receivers in the city centre,
representative receiver locations were selected to monitor noise. Calculations were
then undertaken to assess a potentially worst-case impact.
Sydney City Centre Capacity Improvement 211
Review of Environmental Factors