Correct my noise study

Please help me to correct my study. Thanks

Discussion

During the noise measurement process, some shortcomings with the results came to light. Although these were not serious, further studies of this type would be improved by taking them into account. These shortcomings involved location of measurement, measuring time, construction noise and aircraft noise, all of which would affect the received noise levels and characteristics.

The results of Harbour Green indicate that the predicated results by CRTN expose to be higher than the measurement results. There are some findings regarding the difference of results. Firstly, the prediction noise level at G/F of the building is 82.21 dBA at daytime, but 77.7 dBA is obtained in measurement result at the same level. Low distance attenuation and high percentage of heavy vehicle of lane are both the main reason to establish the difference of noise results. Beside this, the G/F have barrier effect which can reduce the noise level in 10db(A) on account of 2m height concrete barrier installed at highway, but no barrier is installed on the lane. As a result the noise source receiver(NSR) is easily affected by the heavy trucks. In effect, the results show that the 2m height concrete barrier cannot protect any dwelling units and reduce the noise from high traffic flow rate of highway. In addition, the noise prediction of Island Harbour View is also considered in this study. Two predications included with and without the barrier incorporated are considered to oversee the performance. Though there is no any acoustic facilities installed, but 20m height noise barrier is installed in the front of building which is Olympic City I to cover the noise impact area of highway and lane. At high level of dwelling, high noise level have been predicted either at daytime and nighttime as the dwelling is not shielded by the barrier. From the no barrier prediction, the overall noise level keep in high range, but the NSR at G/F have difference of 3 dB compared with the results with barrier. It reflect that the noise barrier have a minor noise reduction from the comparison.

On the other hand, the railway noise prediction to Harbour Green is also assessed in this study. From the result, 65dbA of the sound exposure level (SEL) is obtained by the prediction method and also comply with the Noise Control Ordinance and Hong Kong Planning Standard and Guideline(HKPSG). The insertion loss obtained from the measurement data is similar to the prediction results. It reveals that the rail absorptive enclosure can perform noise reduction as train pass-by the rail. The line also runs at ground level beneath the West Kowloon Highway. The highway acts as a long enclosure and help to prevent the noise emission from train. Although sound absorption material is installed beside a rail, high noise level results have still been obtained from the measurement as two trains pass-by the rail at the same time. The noise may be reflected by other train (figure a). As a result of my site observation, there are some gaps such as the highway and enclosure and electrical control house among the enclosure gap and the length of the enclosure is inadequate to cover the area of Harbour Green.

From the cost estimation, the construction cost of enclosure for railway is HKD 103,000,000 which is the highest cost than the other acoustic facility. The construction of cost of barrier is the lowest in the whole estimation, but it is not a cost effective measures for noise reduction based on the above technical analysis. In other acoustic facility estimation included air conditioner and balconies, the construction cost is less about 5 times of the installation cost of enclosure. Therefore, air conditioner and balconies is one of the cost effective measures to resolve noise pollution problem.

Conclusion

This study has been concerned with methods for predicting the traffic and railway noise at study area. In terms of traffic noise, the two study areas included Harbour Green and Island Harbour View have still been bothered by traffic noise as the barriers have been installed on the highway. Although the barrier is being on the highway, the earlier purpose of the barrier is to protect the old building of the distinct. Therefore, the results show that the new buildings cannot be protected at present. In Island Harbour View area, a private barrier is built in the front of the study area. It is a good design and planning, but the cover area is not adequate to totally protect the dwelling units. The old lane also has a serious noise problem to the area as more heavy trucks pass-by the old lane. According to EIAO, noise problem from old road has not been to consider when the noise level exceed the EPD requipment. The overall performance of traffic noise prediction is over HK guideline 70dB(A) in the study area.

In rail section, the rail noise emission is fully considered before the Harbour Green development. It is because MTRC is one of the investor of the development. The criteria of noise level and insertion loss are achieved as a result of the absorption enclosure. It can protect more dwelling in Harbour Green. Fortunately, the line run under the highway, the noise emission can be allievated and construction cost of enclosure can also be saved. Since the gap, as discussed in earlier part of study, exist in the enclosure design, it would finally damaged the whole performance as noise is generated from the rail in particular lack of noise mitigation design such as floating slab, full enclosure, resilient baseplate, rubber bearing. It is a major deficiency of the enclosure.

Recommendation

Several suggestions for further work can be made on the results. These can be complied in the following items.

1. The provision of new enclosure is restricted by some technical problems such as construction and ventilation, absorption balcony, window insulation, fins and air-conditioner are recommended to install on the building to resolve the noise impact.

2. The provision of acoustic facilities is recommended to install on the rail such as floating slab, full enclosure, resilient baseplate, rubber bearing. It could be improved the noise emission from train pass-by the rail.

3. Enclosure extension and blockage the enclosure gap are highly recommended to resolve the deficiency of enclosure. Otherwise, the noise reduction of the enclosure cannot perform in effective and waste the cost finally.