3               NOISE MONITORING

Monitoring Requirements

3.1          In accordance with Updated EM&A Manual, construction noise monitoring was conducted in terms of the A-weighted equivalent continuous sound pressure level (Leq) to monitor the construction noise arising from the construction activities. The regular monitoring frequency for each monitoring station shall be on a weekly basis and conduct one set of measurements between 0700 and 1900 hours on normal weekdays. Appendix B shows the established Action and Limit Levels for the environmental monitoring works.

 

Monitoring Location

 

3.2          Impact noise monitoring was conducted at the monitoring stations, as shown in Figure 2 according to Table 1.1 of Updated EM&A Manual.  Table 3.1 describes the locations of the noise monitoring stations.

 

Table 3.1         Location of Noise Monitoring Stations

Contract No.

Monitoring Station

Location

ND/2019/01

CP-KTN-NMS5

N/A

ND/2019/06

CP-FLN-NMS1

Belair Monte

 

Monitoring Equipment

 

3.3          Integrating Sound Level Meter was used for impact noise monitoring. The meters are Type 1 sound level meter capable of giving a continuous readout of the noise level readings including equivalent continuous sound pressure level (Leq) and percentile sound pressure level (Lx) that also complied with International Electrotechnical Commission Publications 651:1979 (Type 1) and 804:1985 (Type 1) specifications. Table 3.2 summarizes the noise monitoring equipment being used. Copies of calibration certificates are attached in Appendix C.

 

Table  3.2      Noise Monitoring Equipment

Equipment

Model

Quantity

Integrating Sound Level Meter

SVAN957

2

Sound & Vibration Analyser

BSWA 801

1

Acoustical Calibrator

SV 30A

2

Acoustical Calibrator

4231

1

 

Monitoring Parameters, Frequency and Duration

 

3.4          Table 3.3 summarises the monitoring parameters, frequency and total duration of monitoring.  The noise monitoring schedule is shown in Appendix D.

 

Table 3.3         Noise Monitoring Parameters, Duration and Frequency

             

Contract No.

Monitoring Stations

Parameter

Duration

Frequency

Measurement

ND/2019/01

CP-KTN NMS5

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

Free-field[1]

ND/2019/06

CP-FLN-NMS1

Façade

Remarks:

[1]: Correction of +3dB (A) for Free-field Measurement.

[2]: A-weighted equivalent continuous sound pressure level (Leq). It is the constant noise level which, under a given situation and time period, contains the same acoustic energy as the actual time-varying noise level.

L10 is the level exceeded for 10% of the time. For 10% of the time, the sound or noise has a sound pressure level above L10.

L90 is the level exceeded for 90% of the time. For 90% of the time, the noise level is above this level.

Monitoring Methodology and QA/QC Procedures

 

·         The microphone head of the sound level meter was positioned at 1m from the exterior of the noise sensitive facade and lowered sufficiently so that the building’s external wall acted 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 record during measurement period should be provided; and

·         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 should be checked with a portable wind speed meter capable of measuring the wind speed in m/s.

Maintenance and Calibration

 

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

 

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

 

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

 

Results and Observations

 

3.8          The noise monitoring results are summarised in Table 3.4. Detailed monitoring results and graphical presentations of noise monitoring are shown in Appendix E. The weather information for the reporting month is summarized in Appendix F.

 

Table 3.4        Summary Table of Noise Monitoring Results during the Reporting Month

Contract No.

Monitoring Station

Construction Noise Level

Leq (30 min), dB(A)

Baseline Level, dB(A)

Limit Level, dB(A)

ND/2019/01

CP-KTN-NMS5

54.3-56.5

57.2

75

ND/2019/06

CP-FLN-NMS1

65.9-69.5

69.9

75

 

3.9          All noise monitoring was conducted as scheduled in the reporting month. No complaint was received during the reporting. No Action/Limit Level exceedance was recorded. The summary of exceedance record in reporting month is shown in Appendix H.

 

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

 

Table 3.5         Observation at Noise Monitoring Stations

Contract No.

Monitoring Station

Location

Major Noise Source

ND/2019/01

CP-KTN-NMS5

N/A

Other construction site

not under ND/2019/01

ND/2019/06

CP-FLN-NMS1

Belair Monte

Road Traffic at Ma Sik Road

 

Event and Action Plan

 

3.11       Should any project related non-compliance of the criteria occur, action in accordance with the Action Plan in Appendix G shall be carried out.