Technical Memorandum for the Assessment of Noise from Places Other Than Domestic Premises, Public Places or Construction Sites

2. DETERMINATION OF THE ACCEPTABLE NOISE LEVEL

2.1

General

The appropriate Acceptable Noise Level (ANL) for a particular Noise Sensitive Receiver (NSR) is dependent upon the character of the area within which the NSR is located, and the time of day under consideration.

The steps to be followed in determining an ANL are as follows:

(a)	identify the NSR, in accordance with Section 2.2;

(b)	determine the Area Sensitivity Rating (ASR) of the area within which the NSR is located, in accordance with Section 2.3; and

(c)	determine the ANL from Table 2 in Section 2.4, by reference to the ASR and the time period under consideration.

2.2

Location of the Noise Sensitive Receiver (NSR)

For the purpose of this Technical Memorandum any domestic premises, hotel, hostel, temporary housing accommodation, hospital, medical clinic, educational institution, place of public worship, library, court of law or performing arts centre shall be considered to be a NSR. Any other premises or place, not being in the nature of either industrial or commercial premises, which is considered by the Authority to have a similar sensitivity to noise as the premises and places above shall also be considered to be a NSR. Any premises or place shall, however, be considered to be a NSR only when it is in use for its intended purpose.

2.3

Determination of the Area Sensitivity Rating (ASR)

2.3.1	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 2.3.3. After a careful examination of the area under consideration and the effect of any IFs, the ASR may be determined from Table 1.

2.3.2	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 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. When determining the type of area within which the NSR is located the Authority should not generally take into account the presence of the premises or place from which the noise under investigation is emanating. However, if the Authority considers that such a premises or place by virtue of its size or other characteristics plays a major role in determining the type of area within which the NSR is located, it should be taken into account.

2.3.3	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. An area which consists of a number of factories or industrial establishments; or an establishment which is having industrial operation or operations that is or are of a significant scale is designated as an "industrial area" for the purpose of this Technical Memorandum. 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.

2.3.4	Area Sensitivity Rating (ASR) The Authority shall determine the appropriate ASR for the NSR under consideration from Table 1. Any NSR shall, irrespective of Table 1, be assigned an ASR of "C" if it is within 100 m of a zone designated as "Industrial" or "Industrial Estate" on a statutory Outline Zoning Plan, or an ASR of "B" if it is between 100 m and 250 m from such a zone, except in cases where Table 1 indicates an ASR of "C". Table 1 Area Sensitivity Ratings (ASRs)

Type of Area Containing NSR	Degree to which NSR is affected by IF
Type of Area Containing NSR	Not Affected	Indirectly Affected	Directly Affected
(i) Rural area, including country parks or village type developments	A	B	B
(ii) Low density residential area consisting of low-rise or isolated high-rise developments	A	B	C
(iii) Urban area	B	C	C
(iv) Area other than those above	B	B	C

For the purpose of Table 1, the following definitions 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.


2.4	Determination of the Acceptable Noise Level (ANL) The appropriate ANL, in dB(A), for a given NSR may be determined from Table 2, having regard to the appropriate ASR and the time period under consideration. Table 2 Acceptable Noise levels (ANLs)

Time Period	ASR
Time Period	A	B	C
Day (0700 to 1900 hours)	60	65	70
Evening (1900 to 2300 hours)	60	65	70
Night (2300 to 0700 hours)	50	55	60

Where the noise under investigation is being received within a building from a noise source located on or within the same or an adjoining building such that the noise is transmitted primarily through the structural elements of the building or buildings, the appropriate ANL shall be 10 dB(A) less than the relevant ANL as shown in Table 2. A similar adjustment should be made to the relevant ANL if the point of assessment is at an internal location of a building in which the NSR is located.