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Case studies

Sub-Station Acoustic Monitoring & Modelling


Project Value: £5k

Project Commenced: November 2019

Project Completed: November 2019

Client: Network Rail


About the Project

Equate Design, in conjunction with BCM Construction, were commissioned to measure existing background noise levels surrounding a new sub-station in Tunbridge Wells as well as noise levels generated by the substation installation following complaints received by the client NR from local stakeholders 


The Challenge 

The substation is in operation 24 hours a day and is understood to increase noise emissions when trains are about to pass by. The location consists of a weather enclosure, which is 5 m in height, and houses the power transformer. It was observed on site that the roof and wall panels of the enclosure are separated by approximately 0.3 m gap around the perimeter, which was assumed to provide ventilation to the transformer. The transformer was approximately 32 m away from rear façade of the closest residents and there is an existing 3 m high solid barrier fence located approximately 2 m away from the transformer.  

Requirements were to assess any impact from the installation of the new sub-station in terms of acoustic detrimental effects on local residents, conformance with permitted development noise level requirements and modelling of any mitigation measures that could be implemented if required (e.g. acoustic barrier). 


The Solution 

Measurements were undertaken at five positions with the choice of monitoring positions based on accessibility and on collecting representative noise data in relation to the site.  The surroundings and position used for each monitoring location was located across a variety of different positions including representative receptor locations at the houses of local residents, including at upper storey levels. 

The measurement procedure complied with BS 7445: 1991: ‘Description and measurement of environmental noise, Part 2- Acquisition of data pertinent to land use’. 

Attended noise measurements were undertaken to the rear of the residents’ gardens during the day and night whilst the unattended survey measurements were running automated throughout the period. All measurements were undertaken on a tripod approximately 1.5 m above ground level and in free-field conditions, therefore no reflection correction was applied. The measurement duration for near the residential properties was a minimum 10 minutes. All measurements were undertaken in November 2019. 

Measured noise levels were used to determine noise emissions criteria and noise emissions from the substation. The report presented the results of the environmental surveys followed by acoustic noise modelling of a proposed acoustic screen, noise impact calculations and discussion narrative. 


The Deliverables: 

  • On-site surveying of noise levels both attended and unattended 
  • Acoustic survey report to NR and British standard requirements 
  • Proposals for mitigating measures to reduce impact 
  • Feasibility report on construction of mitigating measures