Noise Prediction

A simplified air-borne noise prediction method is given below. The reader is reminded that the results obtained from the following procedures should be regarded as indicative data only. The prediction method is inapplicable to noise transmitted through building structure. In case of any doubts, the reader is advised to seek independent experts for technical advice.

Step 1 – Identification of the Most Affected Noise Sensitive Receivers (NSR)
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 is considered to be a NSR. In general, the nearest NSR facade with windows, doors or other openings with respect to the concerned noise sources shall be identified.

Step 2 – Sound Power Levels (SWLs) for Noise Sources
Typical SWLs of electrical & mechanical equipment are given in Appendix III for reference. Where practicable, sound power level of individual noise source should be referred to the information provided by the respective manufacturers.

Step 3 – Distance Attenuation
The plan distance or where appropriate, the slant distance between individual noise source and the most affected NSR shall be determined and the corresponding distance attenuation shall be obtained from Table 9. These values shall be subtracted from the individual sound power levels for each noise source to give the individual sound pressure levels for each noise source at the NSR.

Step 4 – Summation of Noise Levels
All individual sound pressure levels for each noise source at the NSR shall be added logarithmically in accordance with Table 10 to give a summed noise level.

Step 5 – Correction for Acoustic Reflections
In case the NSR is a building, a positive correction of 3 dB(A) shall be applied to the noise level obtained in Step 4.

Please note that a correction of 3 dB(A) or 6 dB(A) for tonality, impulsiveness or intermittency may be required to apply to the noise level obtained in step 5. For details, please refer to the Technical Memorandum for the Assessment of Noise from Places other than Domestic Premises, Public Places or Construction Sites.

Table 9: Distance Attenuation at Given Distances