ANNEX C4 Details of Fixed Noise Impact Assessment
|
Appendix C4-1 — Assessment Methodology of Prediction of the Noise Impact from the Existing Pumping Station to Nearby Noise Sensitive Receivers |
|
The theoretical Sound Power Level (SWL) at the source was calculated by the following equation: SWL, dB(A) = SPL + 20 * log D + 8 where SPL = Sound Pressure Level, the averaged noise level measured at distance D D = the distance from noise measurement point to the Source. The SWL values have been taken to represent the source characteristics of the site. The noise from the pumping station was measured at 3m from the air vents. A distance correction of — (20 log D1 + 8) dB has been added to the SWL, in order to predict the noise level just outside the façade of the NSR. D1 is the intervening distance between the point source and the NSR. A façade correction of +3 dB has been added to the SWL to account for the façade reflection effect just outside the NSR. In summary, the predicted noise level (PNL) was calculated using the formula: PNL = CNL - (20 log D + 8) + 3 where CNL = Corrected Noise Level D = the distance from the Source to the proposed noise sensitive receivers. |
|
Appendix C4-2 — Assessment Methodology of Prediction of the Noise Impact from the Proposed Fixed Noise Sources to Nearby Noise Sensitive Receivers |
|
The theoretical Sound Power Level (SWL) at the source was calculated by the following equation: SWL, dB(A) = SPL + 20 * log D + 8 Where SPL = Sound Pressure Level, the averaged noise level measured at distance D D = the distance from noise measurement point to the Source. A distance correction of — (20 log D1 + 8) dB has been added to the SWL, in order to predict the noise level just outside the façade of the NSR. D1 is the intervening distance between the point source and the NSR. In this case, D1 is the shortest possible horizontal distance from identified NSRs to the noise sources. A façade correction of +3 dB has been added to the SWL to account for the façade reflection effect just outside the NSR. In summary, the Maximum Allowable Total Sound Power Level was calculated using the formula: PNL = CNL (or SWL in this case) - (20 log D + 8) + 3 Where CNL = Maximum Allowable Total Sound Power Level at the Fixed Noise Source in this case PNL = Noise Limit - 5 dB(A), i.e. Night time noise level based on SR 'B' (55 dB(A) - 5 dB(A) = 50 dB(A)). i.e. CNL = PNL + (20 log D +8) - 3 |
Table C4.1 : Predicted Fix Noise Impact of the Existing Sewerage Pumping Station at Lee On Estate on the Proposed Wu Kai Sha Development
Existing Sewage Pumping Station
|
Distance for Noise Measurement
|
Dist. Corr.
|
Averaged Measured Noise Level
|
Predicted Noise Level generated by the Pumping Station
|
|||
|
3
|
17.5
|
65.2 dB(A)
|
82.7 dB(A)
|
|||
| NSR | Dist. # | Dist. Corr. | Pumping Staion Noise Level | Predicted Noise Level at the NSR ^ | Acceptable Noise Level * |
Exceed or Not?
|
|
10
|
70
|
44.9
|
82.7 dB(A)
|
40.8 dB(A)
|
50.0 dB(A)
|
Not
|
Table C4.2 : Predicted Maximum Allowable Noise Levels for the Proposed Fixed Noise Sources
|
NSR |
Dist. # |
Dist. Corr. |
Acceptable Noise Level * |
Max. Allowable Noise Level ^ |
|
MOS Wu Kai Sha Station - Public Announcement System |
||||
|
6 |
75 |
45.5 |
50 dB(A) |
92.5 dB(A) |
|
10 |
14 |
30.9 |
50 dB(A) |
77.9 dB(A) |
|
18 |
90 |
47.1 |
50 dB(A) |
94.1 dB(A) |
|
Proposed Salt Water Pumping Station west to the Whitehead Site 2 |
||||
|
24 |
6 |
23.6 |
45 dB(A) |
65.6 dB(A) |
|
Indoor Recreation Centre - Ventilation System |
||||
|
5 |
120 |
49.6 |
60 dB(A) |
106.6 dB(A) |
|
Commercial Centre - Ventilation System |
||||
|
18 |
6 |
23.6 |
60 dB(A) |
80.6 dB(A) |
|
Note: |
|||||||||
|
* : Area Sensitivity Rating "B" is applied for area adjacent to Sai Sha Road, such as Wu Kai Sha Station Development, southern part of Lok Wo Sha Development |
|||||||||
|
As the IRC and Commercial Centre will only operate from 0700 to 2300, daytime and evening noise criterion is applied for these two facilities |
|||||||||
|
Area Sensitivity Rating "A" is applied for the area in Whitehead area, such as Northern part of Lok Wo Sha Development and Whitehead Development Site 1 to 3 |
|||||||||
|
# : Shortest Distance between the proposed noise source and the affected representative NSR |
|||||||||
|
^ : 3 dB(A) façade correction has been considered in the Calculation |
|||||||||