APPENDIX 5.5 SAMPLE CALCULATION OF MARINE TRAFFIC NOISE ASSESSMENT

1. Marine Traffic Noise Prediction -

1.1. The maximum noise level (L_max) during a simultaneous passby of a fishing vessel and the 1 hour equivalent continuous noise levels in (L_{eq, 1 hr}) passby of a fishing vessel and a sampan were predicted at representative NSRs to assess the marine traffic noise.

1.2. For the calculation of the marine traffic noise, the barrier effect of the proposed WFM was ignored as a conservative approach.

2. Predicted maximum passby noise level (L_max) -

2.1. The potential noise impact due to the marine traffic within the assessment area was assessed based on the source noise levels determined by the noise survey. The maximum sound pressure level (L_max2) during a fishing vessel or a sampan passby can be expressed as

L_max2 = L_max1 + 20 log (R₁/R₂) + F (1)

Where, L_max1 is the measured vessel passby noise level, dB(A);

L_max2 is the fishing vessel passby noise level at sensitive receiver, dB(A);

R₁ is the reference distance between measurement point and the fishing vessel/sampan, m;

R₂ is the slant distance between vessel travelling route and sensitive receiver, m.

F is the façade effect correction, taken to be 3 dB(A)

2.2. Two representative navigation paths were assumed for marine traffic noise prediction (see Figure 5.10). The slant distances between the noise sensitive receivers and the assumed routings are tabulated in Tables 1 & 2 below.

Table 1 Slant distances between the receiver and the assumed navigation path – Route 1

NSR ID	Slant distance between each NSR and path segment, m
	1/F	6/F	11/F	16/F	21/F
1b	222	223	225	229	233
2	253	254	256	259	262
3	289	290	291	294	297
4	325	326	327	329	332
5	364	365	366	368	370
15c	202	203	205	208	213
15d	211	212	214	218	222
24a	246	248	250	253	257
24b	229	230	233	236	240
26a	465	466	467	468	470
26b	560	561	561	563	564

Table 2 Slant distances between the receiver and the assumed navigation path – Route 2

NSR ID	Slant distance between each NSR and path segment, m
	1/F	6/F	11/F	16/F	21/F
1b	220	221	223	227	231
2	220	221	223	227	231
3	220	221	223	227	231
4	225	226	228	231	235
5	225	226	228	231	235
15c	225	226	228	231	235
15d	225	226	228	231	235
24a	246	248	250	253	257
24b	229	230	233	236	240
26a	115	117	121	127	134
26b	115	117	121	127	134

Sample calculation at NSR 26a – 1/F (Route 2)

Step 1 : Calculation of the slant distance between the source and the receiver

R₂ = [(h² + D_h²)]^½

= [(10.3-1.4)² + 115²]^½

= 115.3 m

Where, R₂ is the slant distance between the source and the receiver;

h is the receiver height between the receiver height (in mpd) and the height of sea level (in mpd) and;

D_h is the horizontal distance between the source, i.e. the Western Fairway, and the receiver, m;

The determination of the horizontal distance between the source and the receiver is shown in the Figure 5.13.

Step 2 : Calculation of the L_max from the equation (1)

Noise emitted from Vessel, L_max2 = 3 + 67.7 + 20 log (30/115.3)

= 59.0 dB(A)

Noise emitted from Sampan, L_max2 = 3 + 66.6 + 20 log (25/115.3)

= 56.3 dB(A)

3. Predicted 1 hour equivalent continuous noise levels (L_{eq, 1 hr}) -

3.1 The single event noise exposure level (L_AX) for an idealized fishing vessel/sampan (a moving point source) can be expressed as

L_AX = L_max + 10log(Kd/V) (2)

Where, L_max is the measured vessel passby noise level, dB(A);

L_AX is the single event noise level, dB(A);

V is the travelling velocity of fishing vessel/sampan, m/s;

d is the perpendicular distance between measurement point and the fishing vessel/sampan, m;

K is an empirical constant

3.2 As stated in the Transportation Noise Reference Book, K may be less than p in reality, because of either source directivity or possible air absorption. An empirical value of 1.83 for K was suggested for aircraft noise, while a maximum value of 2 for K was estimated for diesel locomotives. For the marine vessel, K is taken as 2 in the noise prediction.

3.3 The single event noise exposure level at the receiver (L_{AX (receiver)}) is determined by applying the distance correction, the angle of view correction and the façade reflection to the L_eq level from Equation (2). The correction for distance attenuation a moving point source is taken as:

D = 20log(d/d_o) (3)

Where, d is the perpendicular slant distance between the source and the receiver, m;

d_o is the reference distance where the source noise level is determined, m.

3.4 Therefore, the single event noise exposure level (L_{AX (receiver)}) for an idealized vessel/sampan can be expressed as

L_{AX (receiver)} = L_{AX (measured)} – D (4)

3.5 The noise level projected to the receiver during the passage of a single vessel/sampan is determined by

L_eq,i = L_AX(receiver) – 10logT (5)

Where, T is the time period under consideration, s.

3.6 If there are N vessels passing by during T, the total predicted noise level (L_eq,total) at the receiver for the passage of these N vessel/sampan is given by

L_{eq, total} = L_{eq, i} + 10logN + 3 dB(A) (6)

Where, 3 dB(A) is the façade effect

3.7 The marine traffic flow data provided by AFCD is shown in the Table 3 below.

Table 3 Marine traffic flow data

Vessel Type	No. of Vessel, Vel/1 hr	Speed, m/s
Sampan	2	2.57 (5 knots)
Fishing Vessel	9

3.8 The speed of fishing vessels and sampan in the acoustic prediction is speed unit for vessel movement within the typhoon shelter.

3.9 Two representative navigation paths were assumed for marine traffic noise prediction (see Figure 5.10). The slant perpendicular distances between the noise sensitive receivers and the assumed routings are tabulated in Tables 4 – 6 below.

Table 4 Perpendicular distances between each NSRs and fishing vessels and sampan’s Route 1 segment 1

Slant perpendicula distance between each NSR and Route 1 segment 1, m
NSR ID	1/F	6/F	11/F	16/F	21/F
1b	215	216	218	222	226
2	250	251	253	256	259
3	285	286	288	290	293
4	325	326	327	329	332
5	360	361	362	364	367
15c	180	182	184	188	193
15d	195	196	199	202	207
24a	141	143	146	151	158
24b	106	109	113	120	128
25	478	479	480	482	484
26a	465	466	467	468	470
26b	580	580	581	582	584

Table 5 Perpendicular distances between each NSRs and fishing vessels and sampan’s Route 1 segment 2

Slant perpendicula distance between each NSR and Route 1 segment 2, m
NSR ID	1/F	6/F	11/F	16/F	21/F
1b	515	516	516	518	520
2	528	529	529	531	532
3	540	541	541	543	544
4	558	559	559	561	562
5	570	571	571	573	574
15c	510	511	511	513	515
15d	517	518	518	520	521
24a	548	549	550	551	553
24b	520	521	522	523	525
25	525	526	527	529	531
26a	520	521	521	523	525
26b	552	553	553	555	556

Table 6 Perpendicular distances between each NSRs and fishing vessels and sampan’s Route 2

Slant perpendicula distance between each NSR and Route 2, m
NSR ID	1/F	6/F	11/F	16/F	21/F
1b	220	221	223	227	231
2	220	221	223	227	231
3	220	221	223	227	231
4	225	226	228	231	235
5	225	226	228	231	235
15c	225	226	228	231	235
15d	225	226	228	231	235
24a	300	301	303	305	309
24b	280	281	283	286	289
25	484	484	484	484	484
26a	115	117	121	127	134
26b	115	117	121	127	134

Sample calculation at NSR 26a - 1/F (Route 2)

Step 1 : Calculation of the slant perpendicular distance between the source and the receiver

R₂ = [(h² + D_h²)]^½

= [(10.3-1.4)² + 115²]^½

= 115.3 m

where, R₂ is the slant perpendicular distance between the source and the receiver;

h is the receiver height between the receiver height (in mpd) and the height of sea level (in mpd) and;

D_h is the perpendicular distance between the source, i.e. the Western Fairway, and the receiver, m;

The determination of the perpendicular distance between the source and the receiver is shown in the Figure 5.14.

Step 2: Calculation of the LAX from the following equations:
LAX = Lmax + 10log(Kd/V)
Where,	K = 2
	V = velocity of fishing vessel/sampan (m/s)
	d = measurement distance
	Lmax = measured Lmax level
	LAX = single event noise exposure level

Equivalent noise level due to passby of a fishing vessel

L_AX = 67.7 + 10log[{(2)(30)}/2.57]

= 81.4

Equivalent noise level due to passby of a sampan

L_AX = 66.6 + 10log[{(2)(25)}/2.57]

= 79.5

Step 3: Calculation of the LAXr from the following equations:
LAXr = LAX – D
Where,	D = 20log (R2/R1)
	R1 = measurement distance
	R2 = slant perpendicular distance between the receiver and route
	LAX = single event noise exposure level
	LAxr = single event noise exposure level at receiver

Equivalent noise level due to passby of a fishing vessel

L_AXr = 81.4 – 20log(115.3/30)

= 69.7

Equivalent noise level due to passby of a sampan

L_AXr = 79.5 – 20log(115.3/25)

= 66.2

Step 4: Calculation of the Leq, i from the following equations:
Leq, i = LAXr - 10logT
Where,	T = time period under consideration, in s, e.g. 1 hour = 3600s
	LAXr = single event noise exposure level at receiver
	Leq, i = the equivalent noise level due to passby of a fishing vessel/sampan

Equivalent noise level due to passby of a fishing vessel

L_{eq, i} = 69.7 - 10log(3600)

= 34.1

Equivalent noise level due to passby of a sampan

L_{eq, i} = 66.2 - 10log(3600)

= 30.6

Step 5: Calculation of the Leq, total from the following equations:
Leq, total = Leq, i +10logN
Where,	N = number of fishing vessel/sampan
	Leq, i = equivalent noise level in due to passing of a fishing vessel/sampan
	Leq, total = total equivalent noise level

Equivalent noise level due to passby of a fishing vessel

L_{eq, total (vessel)} = 34.1 +10log(9)

= 43.7

Equivalent noise level due to passby of a sampan

L_{eq, total (sampan)} = 30.6 +10log(2)

= 33.7

Step 6: Calculation of the total Leq (1 hr):
Total Leq (1 hr) = Leq, total (Vessel ) + Leq, total (Sampan) + 3 dB(A)
Where,	3 dB(A) is the correction for façade effect

Total L_{eq (1 hr)} = L_{eq, total (Vessel )} + L_{eq, total (Sampan)} + 3

=[10 log (10^43.7/10+10^33.7/10)] + 3

= 47.1 dB(A) _#

4. Marine Traffic Noise Prediction Results -

The marine traffic noise preidction results are summarized as follows :

Table 1 Predicted Maximum Passby Noise Level (L_max) – Route 1

NSR ID	Maximum Passby Noise Level, Lmax, dB(A)
	1/F	6/F	11/F	16/F	21/F
1b	53	53	53	53	53
2	52	52	52	52	52
3	51	51	51	51	51
4	50	50	50	50	50
5	49	49	49	49	49
15c	55	55	55	55	55
15d	54	54	54	53	53
24a	52	52	52	52	52
24b	53	53	53	53	53
26a	47	47	47	47	47
26b	45	45	45	45	45

Table 2 Predicted Marine Traffic Noise Level (L_{eq(1 hour)}) – Route 1

NSR ID	1-hour Equivalent Noise Level, Leq(1 hour) dB(A)
	1/F	6/F	11/F	16/F	21/F
1b	42	42	42	42	42
2	41	41	41	41	41
3	40	40	40	40	40
4	39	39	39	39	39
5	39	39	39	39	39
15c	44	44	44	43	43
15d	43	43	43	43	43
24a	46	46	45	45	45
24b	48	48	47	47	46
26a	38	38	37	37	37
26b	36	36	36	36	36

Table 3 Predicted Maximum Passby Noise Level (L_max) – Route 2

NSR ID	Maximum Passby Noise Level, Lmax, dB(A)
	1/F	6/F	11/F	16/F	21/F
1b	53	53	53	53	53
2	53	53	53	53	53
3	53	53	53	53	53
4	53	53	53	53	53
5	53	53	53	53	53
15c	55	55	55	55	55
15d	53	53	53	53	53
24a	52	52	52	52	52
24b	53	53	53	53	53
26a	59	59	59	58	58
26b	59	59	59	58	58

Table 4 Predicted Marine Traffic Noise Level (L_{eq(1 hour)}) – Route 2

NSR ID	1-hour Equivalent Noise Level, Leq(1 hour), dB(A)
	1/F	6/F	11/F	16/F	21/F
1b	41	41	41	41	41
2	41	41	41	41	41
3	41	41	41	41	41
4	41	41	41	41	41
5	41	41	41	41	41
15c	41	41	41	41	41
15d	41	41	41	41	41
24a	39	39	39	39	39
24b	39	39	39	39	39
26a	47	47	47	46	46
26b	47	47	47	46	46