4               Noise Monitoring

Monitoring Requirements

 

4.1         In accordance with EM&A Manual, two noise monitoring stations, namely NMS1 and NMS4 were selected for impact monitoring for the Contract. Impact noise monitoring was conducted for at least once per week during the construction phase of the Contract. Appendix B shows the established Action and Limit Levels for the noise monitoring works.

Monitoring Location

4.2         Impact noise monitoring was conducted at the 2 monitoring stations under the Contract, as shown in Figure 3.  Table 4.1 describes the locations of the air quality monitoring stations.

 

Table 4.1           Location for Air Quality Monitoring Locations

Monitoring Stations

Location

NMS1

Sha Lo Wan

NMS4

San Tau

 

Monitoring Equipment

 

4.3         Table 4.2 summarizes the noise monitoring equipment.  Copies of calibration certificates are provided in Appendix C.

 

Table 4.2           Noise Monitoring Equipment

Equipment

Model and Make

Qty.

Integrating Sound Level Meter

SVAN 957

2

Calibrator

SV 30A

2

 

Monitoring Parameters, Frequency and Duration

 

4.4         Table 4.3 summarizes the monitoring parameters, frequency and total duration of monitoring.  The noise monitoring schedule is shown in Appendix D.

 

Table 4.3           Noise Monitoring Parameters, Frequency and Duration

Monitoring Stations

Parameter

Period

Frequency

NMS1

NMS4

L10(30 min.) dB(A)

L90(30 min.) dB(A)

Leq(30 min.) dB(A) (as six consecutive Leq, 5min readings)

0700-1900 hrs on normal weekdays

Once per week

 

Monitoring Methodology and QA/QC Procedures

 

·          The microphone head of the sound level meter was positioned 1m exterior of the noise sensitive facade and lowered sufficiently so that the building’s external wall acts as a reflecting surface. 

·          The battery condition was checked to ensure the correct functioning of the meter.

·          Parameters such as frequency weighting, the time weighting and the measurement time were set as follows:

—           frequency weighting : A

—           time weighting          : Fast

—           time measurement     : Leq(30 min.) dB(A) (as six consecutive Leq, 5min readings) during non-restricted hours (i.e. 0700-1900 hrs on normal weekdays)

 

·          Prior to and after each noise measurement, the meter was calibrated using a Calibrator for 94.0 dB at 1000 Hz.  If the difference in the calibration level before and after measurement was more than 1.0 dB, the measurement would be considered invalid and repeat of noise measurement would be required after re-calibration or repair of the equipment.

·          During the monitoring period, the Leq, L90 and L10 were recorded.  In addition, site conditions and noise sources were recorded on a standard record sheet.

·          Noise measurement was paused temporarily during periods of high intrusive noise (e.g. dog barking, helicopter noise) if possible and observation was recorded when intrusive noise was not avoided.

·          Noise monitoring was cancelled in the presence of fog, rain, and wind with a steady speed exceeding 5 m/s, or wind with gusts exceeding 10 m/s. The wind speed shall be checked with a portable wind speed meter capable of measuring the wind speed in m/s.

Maintenance and Calibration

 

4.5         The microphone head of the sound level meter and calibrator were cleaned with a soft cloth at quarterly intervals.

 

4.6         The sound level meter and calibrator were checked and calibrated at yearly intervals.

 

4.7         Immediately prior to and following each noise measurement the accuracy of the sound level meter shall be checked using an acoustic calibrator generating a known sound pressure level at a known frequency. Measurements may be accepted as valid only if the calibration levels from before and after the noise measurement agree to within 1.0 dB.

 

Results and Observations

 

4.8         The noise monitoring results are summarized in Table 4.4. Detailed monitoring results and graphical presentations of noise monitoring are shown in Appendices G.

 

 

Table 4.4          Summary Table of Noise Monitoring Results during the Reporting Month

Monitoring Station

Noise Level, Leq (30min) dB(A)

Limit Level

Average

Range

NMS1

68

65 – 71

75 dB(A)

NMS4

58

56 – 62

Remark: +3dB(A) Façade correction included

 

4.9         All noise monitoring was conducted as scheduled in the reporting month.  No Action/Limit Level exceedance was recorded.

 

4.10     According to our field observations, the major noise source identified at the designated noise monitoring stations in the reporting month are as follows:

 

Table 4.5           Observation at Noise Monitoring Stations

Monitoring Station

Major Noise Source

NMS1

Air traffic & marine traffic noise

NMS4

Air traffic & marine traffic noise

 

Event and Action Plan 

 

4.11     Should non-compliance of the criteria occur, action in accordance with the Action Plan in Appendix K shall be carried out.