SILENCING WITH NOISE BARRIERS
We live in a time when the progress of each area of the economy and the improvement of the comfort of life of societies causes an impact on the environment. The world runs forward, buildings are erected, new factories are created, the road network is developing. On the one hand, we have progress, on the other — degradation of the environment. Appropriate measures are used to reduce the negative effects of development. There are always two sides of the coin, and in our case we will consider aspects of environmental protection against noise, which is consistent with the profile of our business. While the development of road infrastructure is a priority, it is necessary to ensure that inconveniences related to noise caused by increased vehicle traffic are as least burdensome as possible. Noise barriers are taken into account when planning new roads, motorways and ring roads. A new road with a noise barrier is now a unity. But not only motorway-type transport routes, railway lines or flyovers are sources of noise. The most common ones also include all types of machinery and equipment, such as motors, turbines, air conditioners, transformers, and sometimes entire production lines.
Operational principle of the noise barrier
Noise barriers are designed to reduce noise — they prevent the spread of noise emitted from its source to the recipient. An object can be classified as a shielded obstacle if its surface density is greater than 10 kg/m2 or when the object has a closed surface without large openings (such as open windows, gates, gaps, etc.), and when the horizontal dimension, perpendicular to the line connecting the end point and the source, is greater than the wavelength λ for the nominal octave band centre frequency.
3 basic features of noise barriers:
- noise barriers with absorptive characteristics,
- noise barriers with diffusion characteristics,
- noise barriers causing diffraction (bending) of the acoustic wave on the upper edge of the barrier and on its sides.
The main function of the noise barrier is to reduce noise. This involves obstructing the spread of noise emitted from the source to the recipient. Simply put, noise reaching the recipient should be as low as possible. If we stand by the road without a barrier, the noise level of passing cars will differ significantly from the one that will reach us if we fenced off from it with a noise barrier. It will be similar in the case of fencing from noisy machines or objects. The noise barrier will act here as a shield. When designing noise barriers, the following are taken into account:
- 1. Noise source and noise recipient,
- 2. Distance from the noise source to the recipient,
- 3. Place where the barrier will be erected,
- 4. Effect to be achieved by the use of the barrier and applicable standards.
Re.1 As we mentioned above, the source of noise can be any machine, vehicle, object causing noise and vibration. Noise recipient — the recipients in factories (workers) will differ from the residents of houses located in the immediate vicinity of a road or a plant.
Re.2 The perfect solution for maximum noise reduction is to locate the noise barrier as close as possible to the source of noise. However, it's not always possible. Then you should position the barrier so as to achieve the intended standards.
Re.3 There is not always a place for the noise barrier to be located directly at the source of noise. Then design the enclosure in such a way that it fulfils its task. The noise barrier will not always be set directly on the ground. We face situations where the barriers are located e.g. on building roofs (to silence the units operating on the roof).
Re.4 Depending on the noise intensity expressed in dB (decibels), you should select the appropriate material with appropriate sound insulation. Some noise barriers have greater sound insulation than others and it makes no sense to use them in places where it is not necessary and could expose the project owner to unnecessary increased project costs. Prior to the planned construction of the noise barrier, confirm the maximum permissible noise level for a given place. Depending on the location of the noise source, standards will vary. This depends on whether we deal with leisure, residential, service, or other areas. The exact standards are given in Table 1.
Noise barrier
Climbing vegetation as a decorative element of the noise barrier — types of climbers:- Hedera helix — Common ivy,
- Hydrangea anomala — Climbing hydrangea,
- Parthenocissus — Virginia creeper,
- Fallopia baldschuanica — Russian-vine,
- Humusus lupulus — Common hop,
- Vitis vinifera — Common grape vine,
- Clematis vitalba — Old man’s beard,
- Clematis alpina — Alpine clematis,
- Wisteria floribunda — Japanese wisteria.
According to the applicable Ordinance of the Minister of Environment of 14/06/2007 on permissible noise levels in the environment (Journal of Laws of 2007, No. 120, item 826), 4 groups of areas are still subject to noise protection.They are listed in the appendix to the Ordinance. Tested areas should be included in the area group appendix provided on our website on the basis of the current intended purpose of the area, unanimously with the applicable development plan or other document confirming the purpose of the tested area.
After specifying the purpose of the area and qualifying it to one of the above-mentioned groups, the permissible noise level expressed by equivalent sound level A is determined. An excerpt of this appendix to the Ordinance is presented below in Table 1. It provides the permissible noise levels in the environment expressed by LAeqD and LAeqN indicators, and the noise levels to be used to determine and check the conditions of use of the environment in relation to one day depending on the purpose of the tested area.
Table 1. Classification of protected areas and permissible values of noise level in the environment expressed in LAeqD and LAeqN (excerpt from Journal of Laws of 2007, No. 120, item 826)