| A.1. |
General Introduction to the Procedures
For the purpose of assessing if a Construction Noise Permit (CNP) may be issued for construction work involving the use of SPME other than percussive piling within a designated area during the restricted hours the Authority shall act in accordance with the following general procedures which are detailed in subsequent sections. The Authority shall:
| (a) |
identify the most affected Noise Sensitive Receiver (NSR), determine the Area Sensitivity Rating (ASR) for the area within which the NSR is located and hence determine the relevant Acceptable Noise Level (ANL) (in accordance with Sections A.2.1 to A.2.6); |
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| (b) |
calculate the Corrected Noise Level (CNL) which will be generated by the construction work at the NSR (in accordance with Sections A.2.7 to A.2.12); and |
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| (c) |
compare the CNL with the ANL to determine if a CNP may be issued (in accordance with Section A.2.13). |
If the CNL is equal to or less than the ANL the CNP may be issued by the Authority in the prescribed form and may include such conditions as the Authority considers appropriate, such as the permissible items of SPME which may be used on the construction site, the hours during which the CNP is valid, the dates of commencement and expiry of the CNP, any noise levels which may not be exceeded at specified locations during specified times and any special noise control measures that must be adopted.
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| A.2. |
Calculation Procedure
| A.2.1 |
Step 1 - Location of the Most Affected Noise Sensitive Receiver (NSR)
The NSR which will be most affected by noise from the construction work shall be identified.
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| A.2.2 |
Step 2 - Determination of the Area Sensitivity Rating (ASR)
| A.2.2.1 |
General
The ASR is a function of the type of area within which the NSR is located and the degree of the effect on the NSR of particular Influencing Factors (IFs) as defined in Section A.2.2.3. After a careful examination of the area under consideration and the effect of any IFs, the ASR may be determined from Table A.1.
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| A.2.2.2 |
Type of area within which the Noise Sensitive Receiver (NSR) is located
The Authority shall have regard to an area of adequate size when determining the type of area within which the NSR is located in accordance with the descriptions in Table A.1. Typically, in urban areas an area of 100 m radius around the NSR should be adequate whereas in sparsely developed areas, such as rural districts, an area of 500 m radius or even more should be considered, depending upon the circumstances. Special factors may dictate that other distances should be used at the discretion of the Authority.
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| A.2.2.3 |
Effect of Influencing Factors (IFs)
For the purpose of this Technical Memorandum any industrial area, major road or the area within the boundary of Hong Kong International Airport shall be considered to be an IF. Industrial areas and the Airport should be regarded as IFs irrespective of the time of day.
The term "industrial area" means an area which consists of a number of factories or industrial undertakings located primarily in purpose-built industrial buildings. It includes any premises, buildings or activities which the Authority deems, by virtue of their acoustical characteristics, make an area industrial in nature. The term "major road" means a road which has a heavy and generally continuous flow of vehicular traffic and, in normal circumstances, means a road with an annual average daily traffic flow in excess of 30,000. Where a major road has an unusually low traffic flow rate (less than 300 vehicles per hour) at the time of day under consideration it shall not be considered as an IF at that time.
In situations where more than one IF affects the NSR to an equal degree only one IF shall be considered.
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| A.2.2.4 |
Area Sensitivity Rating (ASR)
The Authority shall determine the appropriate ASR for the NSR under consideration from Table A.1.
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| A.2.3 |
Step 3 - Determination of the Basic Noise Level (BNL)
The appropriate BNL, in dB(A), for a given NSR may be determined from Table A.2, having regard to the appropriate ASR and the time period as specified in the Construction Noise Permit application.
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| A.2.4 |
Step 4 - Correction for the Duration of the Construction Noise Permit (CNP)
If the duration of an initial CNP, or, in the case of a renewal of a CNP, the combined duration of the initial CNP and any renewal or renewals of a CNP for associated construction work on substantially the same construction site, will be less than or equal to 14 days, a positive correction of 3 dB(A) shall be applied to the BNL.
For the purposes of this Step a CNP shall be considered to be a renewal of a CNP if its date of commencement is less than or equal to 21 days after the expiry date of any other CNP for associated construction work on substantially the same construction site.
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| A.2.5 |
Step 5 - Correction for Multiple Permit Situations
If in the opinion of the Authority the NSR will be materially affected by noise from construction work associated with more than one CNP, the Authority may make such correction to the BNL as it considers appropriate having regard to standard acoustical principles and practices.
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| A.2.6 |
Step 6 - Determination of the Acceptable Noise Level (ANL)
The corrections obtained in Steps 4 and 5 shall be applied to the BNL obtained in Step 3 to give the ANL.
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| A.2.7 |
Step 7 - Location of Items of Specified Powered Mechanical Equipment (SPME)
All items of SPME should be considered to be grouped at a position mid-way between the approximate geographical centre of the construction site and its boundary nearest to the NSR. This position is referred to as the notional source position.
If the construction site is irregular in shape the geographical centre may fall outside the physical limits of the site. In such cases the notional source position shall be taken to be the position on the construction site boundary nearest to the geographical centre of the site. If two such points exist, the point nearest to the NSR shall be used.
If the construction site is linear in shape (that is, long, thin and substantially uniform in width, but not necessarily straight) with a length to width ratio exceeding 5:1, only the dominant portion of the site shall be considered for the purpose of determining the notional source position. The dominant portion is defined as the portion of the linear site closest to the NSR and having a length to width ratio of 5:1. If part of the construction site is linear in shape then such part shall be subject to a separate assessment for a separate CNP, at the discretion of the Authority.
If the construction site is large such that the notional source position would be greater than 50 m from the point on the site boundary nearest to the NSR the position shall be taken to be a point 50 m from that point on the site boundary measured along the line between the approximate geographical centre of the site and the point on the site boundary nearest to the NSR.
If in the opinion of the Authority the site is of such shape or dimensions that the procedure outlined above cannot readily be applied or if such application would lead to an inappropriate notional source position the Authority may select such a notional source position as it considers appropriate in the circumstances.
If the Authority is satisfied that any item of SPME is to remain in substantially the same position, and the particular item and its position has been specified by the applicant, the actual position may be used in conjunction with the notional source position for all other items of SPME in the calculation of distance attenuation in Step 9.
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| A.2.8 |
Step 8 - Sound Power Levels for Specified Powered Mechanical Equipment (SPME)
The sound power levels in dB(A) of each of the items of SPME intended for use on the construction site shall be obtained from Table A.3.
If any item of SPME in Table A.3 intended for use on the construction site is a prescribed product under the Ordinance and is fitted with a valid noise emission label, then the sound power level on the label shall be used instead of the one in Table A.3 for the calculation of CNL.
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| A.2.9 |
Step 9 - Distance Attenuation and Summation of Noise Levels
| A.2.9.1 |
General
In determining the distance from the source position to the NSR blank facades shall not be considered and the distance shall be determined to the nearest NSR facade with windows, doors or other openings. The plan distance or, where appropriate, the slant distance shall be used.
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| A.2.9.2 |
Procedure for Use with a Single Notional Source Position
If all items of SPME are assumed to be located at a single notional source position, the sound power levels obtained in Step 8 shall be summed logarithmically in accordance with Table A.4 to obtain a total sound power level.
The distance between the notional source position and the NSR shall be determined and the appropriate correction factor shall be obtained from Table A.5. This correction factor shall be subtracted from the total sound power level to give the Predicted Noise Level (PNL) at the NSR.
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| A.2.9.3 |
Procedure for Use with Actual Source Positions or a Combination of Actual and Notional Source Positions.
If in addition to a notional source position a number of actual source positions are being used, or if only actual source positions are being used, the distances between the actual source positions and the NSR shall be determined and the appropriate correction factors shall be obtained from Table A.5. These factors shall be subtracted from the individual sound power levels for each item of SPME to give the individual sound pressure levels for each item of SPME at the NSR.
Any combined sound pressure level from items of SPME assumed to be located at a notional source position shall be determined in accordance with Section A.2.9.2 and shall be added logarithmically to the individual sound pressure levels from items of SPME assumed to be at actual source positions, in accordance with Table A.4, to give the PNL at the NSR.
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| A.2.10 |
Step 10 - Corrections for the Effect of Barriers
In cases where the Authority considers that all items of SPME to be used on the construction site will be totally screened by a substantial barrier such that none will be visible when viewed from any window, door or other opening in any facade of the NSR, a negative correction of 10 dB(A) shall be applied to the PNL obtained in Step 9. In cases where the Authority considers a higher negative correction should be applied, the Authority shall use appropriate correction factors having regard to standard acoustical principles and practices.
Substantial barriers shall be taken to be large solid objects, such as buildings or topographical features, which will act as effective acoustic screens. Barriers which are small, lightweight, incomplete or temporary, such as site fences or hoardings, are not to be considered. The effects of purpose-built acoustic barriers may be taken into account in accordance with Section 5.3.
In cases where the Authority considers that all items of SPME to be used on the construction site other than "quiet" items of SPME will be totally screened when viewed from the NSR, a negative correction of 5 dB(A) shall be applied to the PNL obtained in Step 9. For the purpose of this section "quiet" items of SPME shall be considered to be those whose sound power level is more than 15 dB(A) below the total sound power level being generated by all items of SPME.
In cases where the NSR is a building directly adjacent to the construction site such that none of the items of SPME 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 5 dB(A) shall be applied to the PNL obtained in Step 9.
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| A.2.11 |
Step 11 - Corrections for Acoustic Reflections
In cases where the NSR is a building, a positive correction of 3 dB(A) shall be applied to the PNL obtained in Step 9.
An additional positive correction of up to 3 dB(A) may be applied to the PNL in cases where the Authority considers that noise levels at the NSR will be increased due to the confined or reverberant nature of the immediate locality of the construction site or the NSR.
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| A.2.12 |
Step 12 - Corrected Noise Level (CNL) at the Noise Sensitive Receiver (NSR)
The corrections obtained in Steps 10 and 11 shall be applied to the PNL obtained in Step 9 to give the CNL at the NSR.
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| A.2.13 |
Step 13 - Construction Noise Permit (CNP) Issuing Procedure
The CNL at the NSR obtained in Step 12 shall be compared with the ANL obtained in Step 6. If the CNL is equal to or less than the ANL the CNP may be issued. If the CNL is greater than the ANL the CNP shall not be issued unless the application is a special case as defined in Section 5. The procedures detailed in Section 5 shall then be followed.
| Table A.1 Area Sensitivity Ratings (ASRs) |
| Type of Area Containing NSR |
Degree to which NSR is affected by IF
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Not Affected
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Indirectly Affected
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Directly Affected
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| (i) Rural area, including country parks or village type developments |
A
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B
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B
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| (ii) Low density residential area consisting of low-rise or isolated high-rise developments |
A
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B
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C
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| (iii) Urban area |
B
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C
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C
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| (iv) Area other than those above |
B
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B
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C
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For the purpose of Table A.1, the following definitions shall apply:
"country park" means an area that is designated as a country park pursuant to section 14 of the Country Parks Ordinance;
"directly affected" means that the NSR is at such a location that noise generated by the IF is readily noticeable at the NSR and is a dominant feature of the noise climate of the NSR;
"indirectly affected" means that the NSR is at such a location that noise generated by the IF, whilst noticeable at the NSR, is not a dominant feature of the noise climate of the NSR;
"not affected" means that the NSR is at such a location that noise generated by the IF is not noticeable at the NSR; and
"urban area" means an area of high density, diverse development including a mixture of such elements as industrial activities, major trade or commercial activities and residential premises.
| Table A.2 Basic Noise Levels (BNLs) |
| Time Period |
ASR
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A
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B
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C
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| All days during the evening (1900 to 2300 hours), and general holidays (including Sundays) during the day-time and evening (0700 to 2300 hours) |
45
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50
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55
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| All days during the night-time (2300 to 0700 hours) |
30
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35
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40
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| Table A.3 Sound Power Levels for Items of Specified Powered Mechanical Equipment (SPME) |
| Identification Code |
Description |
Sound Power Level (dB(A))
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| CNP 023 |
Breaker, hand-held, mass <= 10kg |
108
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| CNP 024 |
Breaker, hand-held, mass > 10kg and < 20kg |
108
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| CNP 025 |
Breaker, hand-held, mass >= 20kg and <= 35kg |
111
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| CNP 026 |
Breaker, hand-held, mass > 35kg |
114
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| CNP 030 |
Bulldozer |
115
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| CNP 044 |
Concrete lorry mixer |
109
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| CNP 067 |
Dump truck |
117
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| CNP 170 |
Poker, vibratory, hand-held |
113
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| Table A.4 Summation of Noise Levels |
| Difference in dB(A) between two noise levels being summed |
Amount in dB(A) to add to the higher noise level |
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0 to 0.5
1.0 to 1.5
2.0 to 3.0
3.5 to 4.5
5.0 to 7.0
7.5 to 12.0
more than 12.0
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3.0
2.5
2.0
1.5
1.0
0.5
0
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When using Table A.4 noise levels should be summed in a pairwise fashion and the final total rounded to the nearest whole dB(A), with values of 0.5 or more being rounded upwards.
| Table A.5 Correction Factors to Obtain the Predicted Noise Level (PNL) from Sound Power Levels at Given Distances |
| Distance (m) |
Correction (dB(A)) |
Distance (m) |
Correction (dB(A)) |
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0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15 to 16
17 to 18
19 to 21
22 to 23
24 to 26
27 to 29
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8
8
14
18
20
22
24
25
26
27
28
29
30
30
31
32
33
34
35
36
37
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30 to 33
34 to 37
38 to 41
42 to 47
48 to 52
53 to 59
60 to 66
67 to 74
75 to 83
84 to 93
94 to 105
106 to 118
119 to 132
133 to 148
149 to 166
167 to 187
188 to 210
211 to 235
236 to 264
265 to 300
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38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
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For the purpose of determining the correction to be used for converting from sound power level at the source to the PNL at the NSR, the distance from the source position to the NSR shall be determined to the nearest whole metre, with values of 0.5 or more being rounded upwards.
This table is only valid for distances of up to 300 m. For distances greater than 300 m the Authority shall calculate appropriate correction factors having regard to standard acoustical principles and practices.
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