Noise reduction
from the Hamranes
electric substation

hamranes

EFLA Consulting Engineers recently designed various noise control measures for the Hamranes electric substation in Hafnarfjörður, Iceland. At the substation site there are large electric transformers that emit a constant hum which has been bothering nearby residents.

 

The initial stages of the project work consisted of thorough sound level measurements by the substation and in the nearby residential area. In addition, a noise map of the area was made. This analysis work is an essential part of the process, making it possible to assess the situation and design appropriate abatement measures. The noise map was made using an acoustic simulation computer model (SoundPlan) and the map was calibrated to match the sound level measurements, to produce as accurate maps as possible.

 

 hljóðkort fyrir

Noice map of the area before 

 

The analysis work showed, among other things, that the noise from the transformers was mostly low frequency noise, which made the project even more challenging. In general it is more difficult to reduce the propagation of low frequency noise compared to higher frequency noise, e.g. traffic noise. Low frequency sound waves can pass through structures more easily than high frequency sound waves, and because of their long wavelengths, low frequency sound waves can in many cases diffract „around" obstacles, such as noise barriers.

 

Following the analysis work EFLA designed a number of abatement measures, which were design with aid of the acoustic simulation model. Noise barriers around the noisiest transformers in the substation were designed. Due to the magnitude of the low frequency sound energy, it was decided to have the barriers made of concrete and that they would be considerably large (8,5 m high), to provide enough sound reduction. Moreover, the inside face of the noise barriers were covered with sound absorbing materials, to further reduce the sound energy emitted from the transformers.

 

 hljóðkort eftir

Noice map of the area after installation of noise barriers and noice berm

 

In addition to the noise barriers it was decided to increase the height of a noise berm that is located at the substation site boundary, both to reduce the noise propagation and improve the appearance of the substation.

 

EFLA conducted the analysis work, provided the acoustical designs, did the structural design of the noise barriers, provided the landscape design of the noise berm and monitored the construction work.

 

Ístak did the construction work, which is close to being completed now. Once the construction work is completed sound level measurements will take place to assess the overall reduction of noise levels.

 

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