2 NOISE

Monitoring Requirements

2.1 Baseline noise monitoring was conducted daily for a period of at least two weeks at the monitoring station between 6^th January 2010 and 19^th January 2010. Logger function check and calibration was carried out according to manufacturer’s recommendations. The equipment was checked and inspected not less than once every two days after the set up at each monitoring station.

Monitoring Locations

2.2 Table 2.1 gives the location of the monitoring station and is also shown in Figure 2.

Table 2.1 Location of Noise Monitoring Station

Construction Noise Monitoring Stations

Description

Location of Measurement

M9 (Ap Lei Chau PTW)

Mei Chun Court

South Horizons

The Podium of Mei Chun Court, South Horizons

Monitoring Equipment

2.3 Integrating Sound Level Meter was used for noise monitoring. The meter is a Type 1 sound level meter capable of giving a continuous readout of the noise level readings including equivalent continuous sound pressure level (L_eq) and percentile sound pressure level (L_x) and also complied with International Electrotechnical Commission Publications 651:1979 (Type 1) and 804:1985 (Type 1) specifications. Table 2.2 summarizes the noise monitoring equipment being used. Copies of the calibration certificates for the sound level meter and calibrator are attached in Appendix A5.

Table 2.2 Noise Monitoring Equipment

Equipment	Model and Make	Quantity
Integrating Sound Level Meter	SVAN 955 from SVANTEK	1
Calibrator	SV30A from SVANTEK	1

Note: Bruel & Kjaer (B&K) Integrating Sound Level Meters. of Type 2238 and calibrator of Type 4228 are in compliance with the International Electrotechnical Commission Publications 651:1979 (Type1) and 804:1985 (Type1) for sound level meter and 942:1988 Class 1L.

Monitoring Parameters, Frequency and Duration

2.4 In accordance with the updated EM&A Manual, baseline noise for the A-weighted levels L_eq, L₁₀ and L₉₀ was recorded. Data obtained from the baseline noise monitoring was processed and presented according to the following periods:

Ÿ Daytime: 0700-1900 hrs on normal weekdays

Ÿ Evening-time: 1900-2300 hrs

Ÿ Holiday-time: 0700-1900 hrs on holidays

Ÿ Night-time: 2300-0700 hrs of next day

2.5 The frequency and parameters of noise measurement are presented in Table 2.3.

Table 2.3 Frequency and Parameters of Noise Monitoring

Time Period	Duration, min	Parameter
Daytime on normal weekdays (0700-1900 hrs)	30 min	L_eq, L₁₀ & L₉₀
Evening time on all days (1900-2300 hrs) and Holidays (including Sundays) during daytime and evening (0700-1900 hrs)	5 min (3 consecutive L_eq(5min))
All days during the night-time (2300-0700 hrs)	5 min (3 consecutive L_eq(5min))

Monitoring Methodology and QA/QC Procedures

2.6 Table 2.4 summarizes the types of measurement undertaken in the monitoring station.

Table 2.4 Type of Measurement

Monitoring Station	Measurement
M9 (Ap Lei Chau PTW)	Façade measurement

Field Monitoring

2.7 The monitoring procedures are as follows:

· The microphone head of the head 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 good 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

- measurement time : 5 minutes (Leq (30-min) would be determined for daytime noise by calculating the logarithmic average of six Leq (5min) data.)

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

· The wind speed at the monitoring station was checked with the portable wind meter.

· Noise monitoring was carried out continuously for 24 hours during the 14 days baseline monitoring period. Monitoring data was recorded and stored automatically within the sound level meter system. At the end of the monitoring period, noise levels in term of L_eq, L₉₀ and L₁₀ were recorded. In addition, site conditions and noise sources were recorded when the equipment were checked and inspected every two days.

· All the monitoring data within the sound level meter system was downloaded through the computer software, and all these data was checked and reviewed within the computer.

Maintenance and Calibration

2.8 Maintenance and Calibration procedures were as follows:

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

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

· 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

Results

2.9 Baseline noise monitoring was conducted at the designated station in the period between 6^th January 2010 and 19^th January 2010. The monitoring schedule is shown in Appendix B.

2.10 The baseline noise monitoring results are summarized in Table 2.5 to 2.7. All baseline noise monitoring results are given in Appendices A1 to A3. Graphical presentations of the data are provided in Appendix A4.

Table 2.5 Summary of Daytime Noise Monitoring Results (Normal Weekdays)

Daytime 0700-1900 hrs on normal weekdays	Range of Noise Level, dB(A)
	L_eq(30 min)			L₁₀(30 min)			L₉₀(30 min)
	Mean	Max	Min	Mean	Max	Min	Mean	Max	Min
M9	56.5	66.9	43.7	59.0	70.4	46.0	52.0	62.6	40.7

Table 2.6 Summary of Evening-Time & Daytime (Holidays) Noise Monitoring Results

Evening-time 1900-2300 hrs on all days & Daytime 0700-2300 hrs on holidays	Range of Noise Level, dB(A)
	L_eq(5 min)			L₁₀(5 min)			L₉₀(5 min)
	Mean	Max	Min	Mean	Max	Min	Mean	Max	Min
M9	53.1	66.2	46.8	55.6	68.8	47.7	48.9	59.3	45.0

Table 2.7 Summary of Night-Time Noise Monitoring Results

Night-time 2300-0700 hrs of the next day	Range of Noise Level, dB(A)
	L_eq(5 min)			L₁₀(5 min)			L₉₀(5 min)
	Mean	Max	Min	Mean	Max	Min	Mean	Max	Min
M9	49.4	64.6	44.8	51.7	69.7	45.6	46.1	53.0	44.0

Observations

2.11 The weather was generally sunny and cloudy during the baseline monitoring periods. All monitoring was conducted with the wind speed below 5 m/s.

2.12 During the baseline noise monitoring period, the following observations were made which may affect the results:

· Noise source identified at the monitoring station (M9 - Ap Lei Chau PTW) was road traffic noise.

Action and Limit Levels

2.13 The Action and Limit Levels were established in accordance with the approved EM&A Manual. The baseline noise level shall be referenced during the compliance check in the impact noise monitoring period. Table 2.8 presents the Action and Limit Levels for construction noise.

Table 2.8 Action Limit Levels for Noise during Construction Period

Time Period	Action Level	Limit Level
0700-1900 hrs on normal weekdays	When one documented complaint is received	75* dB(A)
0700-2300 hrs on holidays; and 1900-2300 hrs on all other days		60/65/70** dB(A)
2300-0700 hrs of next day		45/50/55** dB(A)

(*) reduce to 70 dB(A) for schools and 65 dB(A) during school examination periods.

(**) to be selected based on Area Sensitivity Rating.