# On the Control of Low-Frequency Audible Noise from Electrical Substations: A Case Study
###### Abstract  
With the world facing the urgency of energy transition, the development of efficient and quiet electrical infrastructures is of topical importance in the construction of the environment of the future. The problem of noise from power distribution systems is often underestimated, although several works in the literature underline the effect of disturbance on the population, especially concerning the low frequency range. This paper overviews the issue of the low-frequency noise generated by electrical substations, from the experimental characterization of the source to the possible mitigation measures at the source, along the propagation path and at the receiver. Alongside the general presentation, a case study serves as a practical demonstration of the proposed methodological approach. It was found that in the investigated situation the main disturbance comes from the transformer at two low-frequency harmonics of twice the networking frequency. A traditional noise barrier is designed taking into account the strict size constraints imposed by technical compatibility with the electrical infrastructure, which limits its efficacy at low frequency. Noise masking with broadband signals can be a complementary solution to further reduce noise disturbance and contain it within prescribed limits. The evaluation of subjective response of the receivers to different mitigation solutions is made possible by the availability of the impulse response. noise barrier; power substation; transformer noise; low-frequency noise; noise masking Article  
On the Control of Low-Frequency Audible Noise  
from Electrical Substations: A Case Study  
[PERSON] and [PERSON]  
2 Laboratory of Acoustics, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Heverlee, Belgium; [EMAIL_ADDRESS]  
[EMAIL_ADDRESS]  
16 December 201913 January 20202016 January 202016 December 201913 January 20202016 January 202016 December 201913 January 20202016 January 202016 January 202016 December 20201913 January 20202016 January 202016  
residential areas is particularly important because the generated noise can be very high (75-85 dB(A) 1 m far from the transformer case). [PERSON] [8] discusses the noise of substations, pointing out that distance plays an important role, but it cannot be considered an absolute factor: if substations are closer to urban areas, noise is less attenuated but the background noise is higher than in rural areas where it can be as low as 20-25 dB(A). Moreover, the attenuation of air depends on frequency, and thus it can change the spectrum of the noise over distance. Passive methods to abate noise are mainly focused at the source or along the propagation path. The first group of measures encompasses careful design and operation of the infrastructure, including the choice of the location: the substation should preferably be built underground, or at least as distant as possible from residential centers, in large isolated areas with a high background noise. [PERSON] et al. [9] state that \"if it is properly taken into account during the design phase\", noise is not a problem in new installations, thus implying that indeed it might be an issue when not thoroughly considered, or in the case of expansion of existing installations, which are usually stretched to the limit. When designing or revamping a power substation, equipment with noise emissions below the manufacturer's standard can be required to reduce continuously radiated discrete tones [8], impulse noise [10] and corona discharge noise [11]. In particular, the transformer is the element that is more likely to raise complaints, especially when its rating is high. The transformer consists of three main parts: the primary coil and the secondary coil around the laminated core, and the air handling units. Noise generation in transformers is a vibro-acoustic problem, since Lorentz forces induced by the high currents flowing through the coils typically cause vibrations at twice the networking frequency and its harmonics.