- 9
2.10 Step 10
Corrections for the Effect of Barriers
In cases where the Authority considers that all items of PME to
totally screened by a
be used on the construction site will be
substantial barrier when viewed from the NSR, a negative correction of 10dB(A) shall be applied to the PNL obtained in Step 9.
Substantial barriers shall be taken to be large solid objects,
such as buildings or topographical features,
acoustic screens. Barries which are small,
which will act as effective
lightweight, incomplete or
are not to be considered.
temporary, such as site fences or hoardings,
The effects of purpose-built acoustic barriers may be taken into account
in accordance with Section 3.1.
In cases where the Authority considers that all items of PME to
be used on the onstruction site other than "quiet" items of PME will be
totally screened when viewed from the NSR, a negative correction of 5dB(A) shall be applied to the PNL obtained in Step 9. For the purpose
of this section "quiet" items of PME shall be considered to be those
whose sound power level is more than 15dB(A) below the total sound power
level being generated by all items of PME.
In cases where the NSR is a building directly adjacent to the
construction site such that none of the items of PME to be used on the
construction site will be visible when viewed from any window,
door or
other opening in any facade of the NSR, the NSR shall be considered to be
partially screened and a negative correction of 5dB(A) shall be applied
to the PNL obtaianed in Step 9. Where the latter condition applies and the NSR is separated from the construction site by another building such
that none of the items of PME will be visible when viewed from any window, door or other opening in any facade of the NSR, the NSR shall be considered to be totally screened.
2.11 Step 11 Corrections for Acoustic Reflections
In cases where the NSR is a building, a positive correction of 3dB(A) shall be applied to the PNL obtained in Step 9.