Appendix 5 Noise Calculations for Grab Dredger Option between
23:00 and 07:00
The dredgers allocation and
working schedules as described in Section 5.3.4 are adopted. For each NSR under consideration, the noise
levels due to one grab dredger in each sub-divided working zone are first
individually calculated as shown in Table A5.1 to A5.6. The relevant individual noise levels are
then combined to obtain the resultant noise levels at each NSR for all scenarios
as shown in Table A5.7.
Table
A5.1 Noise levels (Leq(5min)) at Long Tsai
Tsuen/Hung Shing Ye (NSR a) due to one grab dredger in each sub-divided working zone
|
Working Zone |
Shortest distance from NSR (m) |
Distance attenuation (dBA) |
Air absorption correction |
Facade correction (dBA) |
Attenuation # due to screening (dBA) |
Noise level at NSR (dBA) |
|
ABn (north) |
1765 |
-72.9 |
-4.8 |
3.0 |
-5 |
321 |
|
ABn (south) |
1800 |
-73.1 |
-4.9 |
3.0 |
0 |
372 |
|
ABs (north) |
1900 |
-73.6 |
-5.1 |
3.0 |
0 |
363 |
|
ABs (south) |
2067 |
-74.3 |
-5.6 |
3.0 |
0 |
354 |
|
BCn (north) |
2333 |
-75.3 |
-6.3 |
3.0 |
0 |
335 |
|
BCn (south) |
2600 |
-76.3 |
-7.0 |
3.0 |
0 |
32 |
|
BCs (north) |
2933 |
-77.3 |
-7.9 |
3.0 |
0 |
30 |
|
BCs (south) |
3266 |
-78.3 |
-8.8 |
3.0 |
0 |
28 |
# The 2nd
last column refers to the topographic screening due to intervening hills.
Table
A5.2 Noise levels (Leq(5min)) at Ko Long
(NSR b) due to one
grab dredger in each sub-divided working zone
|
Working Zone |
Shortest distance from NSR (m) |
Distance attenuation (dBA) |
Air absorption correction |
Facade correction (dBA) |
Attenuation # due to screening (dBA) |
Noise level at NSR (dBA) |
|
ABn (north) |
1000 |
-68.0 |
-2.7 |
3.0 |
0 |
44 |
|
ABn (south) |
1133 |
-69.1 |
-3.1 |
3.0 |
-10 |
33 |
|
ABs (north) |
1400 |
-70.9 |
-3.8 |
3.0 |
-10 |
30 |
|
ABs (south) |
1733 |
-72.8 |
-4.7 |
3.0 |
-10 |
28 |
|
BCn (north) |
2100 |
-74.4 |
-5.7 |
3.0 |
-10 |
25 |
|
BCn (south) |
2500 |
-75.9 |
-6.8 |
3.0 |
-10 |
22 |
|
BCs (north) |
2867 |
-77.1 |
-7.7 |
3.0 |
-10 |
20 |
|
BCs (south) |
3267 |
-78.3 |
-8.8 |
3.0 |
-10 |
18 |
# The 2nd
last column refers to the topographic screening due to intervening hills.
Table
A5.3 Noise levels (Leq(5min)) at Yung Shue
Wan (NSR c) due to
one grab dredger in each sub-divided working zone
|
Working Zone |
Shortest distance from NSR (m) |
Distance attenuation
(dBA) |
Air absorption correction |
Facade correction (dBA) |
Attenuation # due to screening (dBA) |
Noise level at NSR (dBA) |
|
ABn (north) |
1175 |
-69.4 |
-3.2 |
3.0 |
0 |
42 |
|
ABn (south) |
1367 |
-70.7 |
-3.7 |
3.0 |
0 |
41 |
|
ABs (north) |
1667 |
-72.4 |
-4.5 |
3.0 |
-5 |
33 |
|
ABs (south) |
2000 |
-74.0 |
-5.4 |
3.0 |
-10 |
26 |
|
BCn (north) |
2367 |
-75.5 |
-6.4 |
3.0 |
-10 |
23 |
|
BCn (south) |
2750 |
-76.8 |
-7.4 |
3.0 |
-10 |
21 |
|
BCs (north) |
3133 |
-77.9 |
-8.5 |
3.0 |
-10 |
19 |
|
BCs (south) |
3533 |
-78.9 |
-9.5 |
3.0 |
-10 |
17 |
# The 2nd
last column refers to the topographic screening due to intervening hills.
Table
A5.4 Noise levels (Leq(5min)) at Tai Wan
San Tsuen (NSR d) due
to one grab dredger in each sub-divided working zone
|
Working Zone |
Shortest distance from NSR (m) |
Distance attenuation (dBA) |
Air absorption correction |
Facade correction (dBA) |
Attenuation # due to screening (dBA) |
Noise level at NSR (dBA) |
|
ABn (north) |
1410 |
-71.0 |
-3.8 |
3.0 |
0 |
40 |
|
ABn (south) |
1500 |
-71.5 |
-4.1 |
3.0 |
0 |
39 |
|
ABs (north) |
1700 |
-72.6 |
-4.6 |
3.0 |
-10 |
28 |
|
ABs (south) |
1967 |
-73.9 |
-5.3 |
3.0 |
-10 |
26 |
|
BCn (north) |
2333 |
-75.3 |
-6.3 |
3.0 |
-10 |
23 |
|
BCn (south) |
2667 |
-76.5 |
-7.2 |
3.0 |
-10 |
21 |
|
BCs (north) |
3033 |
-77.6 |
-8.2 |
3.0 |
-10 |
19 |
|
BCs (south) |
3400 |
-78.6 |
-9.2 |
3.0 |
-10 |
17 |
# The 2nd
last column refers to the topographic screening due to intervening hills.
Table
A5.5 Noise levels (Leq(5min)) at YMCA
Lamma Island Youth Hostel (NSR e) due to one grab dredger in each sub-divided working zone
|
Working Zone |
Shortest distance from NSR (m) |
Distance attenuation (dBA) |
Air absorption correction |
Facade correction (dBA) |
Attenuation # due to screening (dBA) |
Noise level at NSR (dBA) |
|
ABn (north) |
2200 |
-74.8 |
-5.9 |
3.0 |
0 |
34 |
|
ABn (south) |
2050 |
-74.2 |
-5.5 |
3.0 |
0 |
35 |
|
ABs (north) |
2050 |
-74.2 |
-5.5 |
3.0 |
0 |
35 |
|
ABs (south) |
2133 |
-74.6 |
-5.8 |
3.0 |
0 |
35 |
|
BCn (north) |
2333 |
-75.3 |
-6.3 |
3.0 |
0 |
33 |
|
BCn (south) |
2400 |
-75.6 |
-6.5 |
3.0 |
0 |
33 |
|
BCs (north) |
2633 |
-76.4 |
-7.1 |
3.0 |
0 |
32 |
|
BCs (south) |
2900 |
-77.2 |
-7.8 |
3.0 |
0 |
30 |
# The 2nd
last column refers to the topographic screening due to intervening hills.
Table
A5.6 Noise levels (Leq(5min)) at Lo So
Shing (NSR f) due to
one grab dredger in each sub-divided working zone
|
Working Zone |
Shortest distance from NSR (m) |
Distance attenuation (dBA) |
Air absorption correction |
Facade correction (dBA) |
Attenuation # due to screening (dBA) |
Noise level at NSR (dBA) |
|
ABn (north) |
2500 |
-75.9 |
-6.8 |
3.0 |
0 |
32 |
|
ABn (south) |
2233 |
-75.0 |
-6.0 |
3.0 |
0 |
34 |
|
ABs (north) |
2100 |
-74.4 |
-5.7 |
3.0 |
0 |
35 |
|
ABs (south) |
1900 |
-73.6 |
-5.1 |
3.0 |
0 |
36 |
|
BCn (north) |
1880 |
-73.5 |
-5.1 |
3.0 |
0 |
36 |
|
BCn (south) |
2000 |
-74.0 |
-5.4 |
3.0 |
0 |
36 |
|
BCs (north) |
2000 |
-74.0 |
-5.4 |
3.0 |
0 |
36 |
|
BCs (south) |
2233 |
-75.0 |
-6.0 |
3.0 |
0 |
34 |
# The 2nd
last column refers to the topographic screening due to intervening hills.
Table
A5.7 Resultant noise levels (Leq(5min)) in dB(A) at
each NSR
|
Month |
NSR
a |
NSR
b |
NSR
c |
NSR
d |
NSR
e |
NSR
f |
|
Month 1 |
42* |
45 |
45 |
43 |
42 |
42 |
|
Month 2 |
42 |
45 |
45 |
43 |
42 |
42 |
|
Month 3 |
42 |
45 |
45 |
43 |
42 |
42 |
|
Month 4 |
42 |
45 |
45 |
43 |
42 |
42 |
|
Month 5 |
42 |
45 |
45 |
43 |
42 |
42 |
|
Month 6 |
41 |
45 |
45 |
43 |
41 |
42 |
|
Month 7 |
41 |
35 |
41 |
40 |
40 |
42 |
|
Month 8 |
41 |
35 |
41 |
40 |
40 |
42 |
Footnote:
*Sample Calculation:
For NSR a in Month 1,
1Noise level due to GD1 at ABn North = 32
dB(A)
2Noise level due to GD2 at ABn South = 37
dB(A)
3Noise level due to GD3 at ABs North = 36
dB(A)
4Noise level due to GD4 at ABs South = 35
dB(A)
5Noise level due to GD5 at BCn North = 33
dB(A)
Resultant noise level = 42
dB(A)