Advances in Acoustic Modelling of Overhead Transmission Lines

(TSOs) worldwide. Addressing this issue often entails substantial investments in existing infrastructure and may require temporary outages. In the context of growing global awareness of environmental noise pollution and increasingly stringent regulatory requirements, it is essential to implement reliable methodologies for assessing noise levels in the vicinity of planned lines already during the design phase, as well as for evaluating the impact of mitigation measures on existing lines. Performing such assessments prior to the construction or reconstruction of overhead lines is particularly important to ensure compliance with national legislation on audible noise.

Corona discharge is the dominant source of audible noise on high-voltage (HV) overhead transmission lines. Due to the time-varying nature of corona activity, its spectral content, and its spatial distribution along the line, an accurate representation of overhead lines as acoustic sources is highly complex and cannot be fully addressed by purely analytical methods. Since audible noise is typically most pronounced under wet-weather conditions, several semiempirical approaches developed from extensive experimental studies conducted in the 1970s remain widely used today.

While semi-empirical methods provide estimates of noise levels at specific distances from an overhead line, they do not, on their own, allow for a comprehensive assessment of the spatial distribution of noise in the surrounding area. To evaluate the actual environmental impact and potential exceedance of regulatory limits, it is necessary to account for sound propagation, terrain, ground characteristics, vegetation, and nearby structures. Noise mapping techniques, as a general method for environmental noise assessment, are based on source characterisation, numerical modelling, and standardised sound propagation algorithms, and offer an effective means of addressing these requirements. Advances in computational modelling enable the efficient generation of noise maps, supporting the evaluation of noise exposure, comparison with ambient conditions, and assessment of mitigation measures.

In this paper, we propose an advanced methodology for calculating the sound field around overhead transmission lines, using industry-standard noise prediction software implementing international standards for outdoor sound propagation, integrated within the CNOSSOS-EU framework. The core of the methodology is the representation of an overhead line as an acoustic source.

Verification through comparison with field measurements demonstrates that the proposed methodology represents a significant advancement in the acoustic modelling of overhead transmission lines. The methodology supports informed decision-making during planning and reconstruction phases, contributing to environmentally compliant and socially responsible transmission infrastructure.