TNAG-1613-FCO40-2221-Executive-Council-of-Hong-Kong-memoranda-and-minutes-of-meet-1987 — Page 269

- 9

3.3.3

Correction for Impulsiveness

If the noise under investigation is considered by the Authority to be impulsive in character a positive correction, Cimp, of not more than

3 dB(A) may be applied to the MNL.

3.3.4

Correction for Intermittency

A correction for intermittency shall be applied to the MNL, for the night-time period (2200 to 0700 hours) only, when the A-weighted sound pressure level of the noise under investigation is subject to rapid changes in level of 5.0 dB or more occuring with a degree of regularity within the STP, the typical magnitude of these changes in level being known as the intermittency factor, f fint.

Where the noise under

intermittent characteristic

investigation is assessed to have an

with an intermittency factor, f

correction, Cint' to the MNL shall be as shown in Table 5.

the

int'

|

Table 5

Intermittency Correction

fint (dB)

| Cint (dB(A))

greater than or equal to 5.0 and less than 10.0

3

6

greate

greater than or equal to 10.0

3.3.5

Calculation of Corrected Noise Level (CNL)

The CNL shall be calculated by applying the appropriate corrections to the MNL in accordance with the following formula :-

CNL

MNL

+

Ctone

Simp

Cint

dB(A)