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Audible substation noise

Audible substation noise, particularly continuously radiated discrete tones (e.g., from power transformers), is the type of noise that the community may find unacceptable. Community guidelines to ensure that acceptable substation noise levels are maintained can take the form of governmental regulations or individual/community reaction (permit denial, threat of complaint to utility regulators, etc.).

Problems with audible substation noise
Problems with audible substation noise (photo credit:

Where noise is a potential concern, field measurements of the area background noise levels and computer simulations predicting the impact of the substation may be required.

The cost of implementing noise reduction solutions (low-noise equipment, barriers or walls, noise cancellation techniques, etc.) may become a significant factor when a site is selected.

As you already know, noise can be transmitted as a pressure wave either through the air or through solids. The majority of cases involving the observation and measurement of noise have dealt with noise being propagated through the air.

However, there are reported, rare cases of audible transformer noise appearing at distant observation points by propagating through the transformer foundation and underground solid rock formations.

It is best to avoid the situation by isolating the foundation from bedrock where the conditions are thought to favor transmission of vibrations.

Let’s analyse the following topics in order to fully understand the problems that create audible substation noise:

  1. Substation Noise Sources
  2. Typical Substation Noise Levels
  3. Governmental Regulations
  4. Noise Abatement Methods

1. Substation Noise Sources

Continuous audible sources

The most noticeable audible noise generated by normal substation operation consists of continuously radiated audible discrete tones. Noise of this type is primarily generated by power transformers. Regulating transformers, reactors, and emergency generators, however, could also be sources.

This type of noise is most likely to be subject to government regulations. Another source of audible noise in substations, particularly in extra high voltage (EHV) substations, is corona from the bus and conductors.

Continuous radio frequency (RF) sources

Another type of continuously radiated noise that can be generated during normal operation is RF noise. These emissions can be broadband and can cause interference to radio and television signal reception on properties adjacent to the substation site.

Objectionable RF noise is generally a product of unintended sparking, but can also be produced by corona.

Impulse sources

While continuously radiated noise is generally the most noticeable to substation neighbors, significant values of impulse noise can also accompany normal operation. Switching operations will cause both impulse audible and RF noise with the magnitude varying with voltage, load, and operation speed.

Circuit breaker operations will cause audible noise, particularly operation of air-blast breakers.

Go back to Substation Noise Topics ↑

2. Typical Substation Noise Levels

Equipment noise levels

Equipment noise levels may be obtained from manufacturers, equipment tendering documents, or test results. The noise level of a substation power transformer is a function of the MVA and BIL rating of the high voltage winding. These transformers typically generate a noise level ranging from 60 to 80 dBA.

Transformer noise will “transmit” and attenuate at different rates depending on the transformer size, voltage rating, and design.

Few complaints from nearby residents are typically received concerning substations with transformers of less than 10 MVA capacity, except in urban areas with little or no buffers. Complaints are more common at substations with transformer sizes of 20-150 MVA, especially within the first 170-200 m (500-600 ft).

However, in very quiet rural areas where the nighttime ambient can reach 20–25 dBA, the noise from the transformers of this size can be audible at distances of 305 m (1000 ft) or more.

In urban areas, substations at 345 kV and above rarely have many complaints because of the large parcels of land on which they are usually constructed.

Attenuation of noise with distance

The rate of attenuation of noise varies with distance for different types of sound sources depending on their characteristics. Point sound sources that radiate equally in all directions will decrease at a rate of 6 dB for each doubling of distance.

Cylindrical sources vibrating uniformly in a radial direction will act like long source lines and the sound pressure will drop 3 dB for each doubling of distance. Flat planar surfaces will produce a sound wave with all parts of the wave tracking in the same direction (zero divergence).

Hence, there will be no decay of the pressure level due to distance only. The designer must first identify the characteristics of the source before proceeding with a design that will take into account the effect of distance.

A transformer will exhibit combinations of all of the above sound sources, depending on the distance and location of the observation point. Because of its height and width, which can be one or more wavelengths, and its nonuniform configuration, the sound pressure waves will have directional characteristics with very complex patterns. Close to the transformer (near field), these vibrations will result in lobes with variable pressure levels.

Hence, the attenuation of the noise level will be very small. If the width (W) and height (H) of the transformer are known, then the near field is defined, from observation, as any distance less than 2√WH from the transformer.

Further from the transformer (far field), the noise will attenuate in a manner similar to the noise emitted from a point source. The attenuation is approximately equal to 6 dB for every doubling of the distance.

In addition, if a second adjacent transformer produces an identical noise level to the existing transformer (e.g., 75 dBA), the total sound will be 78 dBA for a net increase of only 3 dB. This is due to the logarithmic effect associated with a combination of noise sources.

Go back to Substation Noise Topics ↑

3. Governmental Regulations

Governmental regulations may impose absolute limits on emissions, usually varying the limits with the zoning of the adjacent properties. Such limits are often enacted by cities, villages, and other incorporated urban areas where limited buffer zones exist between property owners.

Typical noise limits at the substation property line used within the industry are as follows:

  • Industrial zone
  • Commercial zone
Additional governmental noise regulations address noise levels by limiting the increase above the existing ambient to less than 10 dB. Other regulations could limit prominent discrete tones, or set specific limits by octave bands.

Go back to Substation Noise Topics ↑

4. Noise Abatement Methods

The likelihood of a noise complaint is dependent on several factors, mostly related to human perceptions. As a result, the preferred noise abatement method is time-dependent as well as site specific.

Reduced transformer sound levels

Since power transformers, voltage regulators, and reactors are the primary sources of continuously radiated discrete tones in a substation, careful attention to equipment design can have a significant effect on controlling noise emissions at the substation property line.

This equipment can be specified with noise emissions below manufacturers’ standard levels, with values as much as 10 dB below those levels being typical.

In severely restrictive cases, transformers can be specified with noise emissions 20 dB less than the manufacturers’ standard levels, but usually at a significant increase in cost. Also, inclusion of bid evaluation factor(s) for reduced losses in the specification can impact the noise level of the transformer. Low-loss transformers are generally quieter than standard designs.

Low-impulse noise equipment

Outdoor type switching equipment is the cause of most impulse noise. Switchgear construction and the use of vacuum or puffer circuit breakers, where possible, are the most effective means of controlling impulse emissions.

The use of circuit switchers or air-break switches with whips and/or vacuum bottles for transformer and line switching, may also provide impulse-emission reductions over standard air-break switches.

Switch Interrupter with single bottle vacuum
Switch Interrupter with single bottle vacuum (photo credit:

RF noise and corona induced audible noise control

Continuously radiated RF noise and corona induced audible noise can be controlled through the use of corona free hardware and shielding for high voltage conductors and equipment connections, and through attention to conductor shapes to avoid sharp corners.

Angle and bar conductors have been used successfully up to 138 kV without objectionable corona if corners are rounded at the ends of the conductors and bolts are kept as short as possible.

Tubular shapes are typically required above this voltage. Pronounced edges, extended bolts, and abrupt ends on the conductors can cause significant RF noise to be radiated. The diameter of the conductor also has an effect on the generation of corona, particularly in wet weather.

Increasing the size of single grading rings or conductor diameter may not necessarily solve the problem. In some cases it may be better to use multiple, smaller diameter grading rings.

Site location

For new substations to be placed in an area known to be sensitive to noise levels, proper choice of the site location can be effective as a noise abatement strategy. Also, locations in industrial parks or near airports, expressways, or commercial zones that can provide almost continuous background noise levels of 50 dB or higher will minimize the likelihood of a complaint.

Larger yard area

Substation noise intensity varies inversely with distance. An effective strategy for controlling noise of all types involves increasing the size of the parcel of real estate on which the substation is located.

Equipment placement

Within a given yard size, the effect of noise sources on the surroundings can be mitigated by careful siting of the noise sources within the confines of the substation property.

In addition, making provisions for the installation of mobile transformers, emergency generators, etc. near the center of the property, rather than at the edges, will lessen the effect on the neighbors.

Barriers or walls

If adequate space is not available to dissipate the noise energy before it reaches the property line, structural elements might be required. These can consist of walls, sound-absorbing panels, or deflectors. In addition, earth berms or below-grade installation may be effective. It may be possible to deflect audible noises, especially the continuously radiated tones most noticeable to the public, to areas not expected to be troublesome.

Foliage, despite the potential aesthetic benefit and psychological effect, is not particularly effective for substation noise reduction purposes.

Properly constructed sound barriers can provide several decibels of reduction in the noise level. An effective barrier involves a proper application of the basic physics of:

  1. Transmission loss through masses
  2. Sound diffraction around obstacles
  3. Standing waves behind reflectors
  4. Absorption at surfaces

For a detailed analysis of wall sound barriers, refer to IEEE Std. 1127-2013.

Active noise cancellation techniques

Another solution to the problem of transformer noise involves use of active noise control technology to cancel unwanted noise at the source, and is based on advances in digital controller computer technology. Active noise cancellation systems can be tuned to specific problem frequencies or bands of frequencies achieving noise reduction of up to 20 dB.

Go back to Substation Noise Topics ↑

Reference // Electric Power Substations Engineering by James H. Sosinski / Consumers Energy

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More Information

Edvard Csanyi

Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV/MV switchgears and LV high power busbar trunking (<6300A) in power substations, commercial buildings and industry facilities. Professional in AutoCAD programming.


  1. Paula M
    Jan 03, 2023

    I moved in to new house in March 2022.
    Substation is located in part of our garden, noise level is horrible.We cannot open windows ,because of the noise.we have a son who’s autistic,and his got anxiety because of the noise coming from substation.I’ve contacted local Enforcement Officer who’s done some measuring,and they saying that is below noise level. UKPN don’t want to take any action. What to do? Where to ask for help?

  2. Jerry D Johnson
    Jun 16, 2022

    Dear sir, I live across the street from a large pge substation. The sound level is un believable. Some 10-20 years ago I complained to I think pge and someone actually came out and stood on my front porch around 2am and measured the noise level. At that time the elderly gentleman that measured the levels said it was to loud and that since I was on the cheaper side of the substation they have most the sound coming towards my house. The man said tey could build a wall inside the substation yard and direct or deflect some of the noise away from the homes directly evolved. I’m really not sure why no one followed up on doing anything and since I quit complaining for a minute nothing happened.
    I need to find out who I can contact to proceed forward with getting something done. The noise in my house is crazy and since they have been adding on to the substation my headaches are more frequent and I’m just putting 2 and 2 together. Please, any help in contacting a government agency to help with this would be greatly appreciated. I’m sure the way the wall around the substation is open in spots directly infront of my house something could be done to lessen the noise level.. thank you for any help.
    Sincerely, Jerry Johnson

  3. Steve Thomas
    Mar 29, 2022

    I live in a rural area and the power company just put in a large 3 bank of transformers on a two poles. The buzzing is loud. the bigger problem is that my autistic daughter can no longer go on our patio which is 80ft away from the new transformers. I never had anything there before. there are other places near by that they could have been put. what do you think my options are? I am not getting anywhere with the power company. Do i go to court? thank you

  4. Jon Morris
    Mar 16, 2022

    Hello Mr Csanyi,

    I just purchased & moved into a new home in Wheatland Wyoming. About 170 ft from the back of the house is a small sub station. One transformer. But the hum/buzz is most audible when the patio door is opened and just setting on the patio. I was thinking of building a cinder block wall down by it at least 6 ft high and 50 ft long which is about the width of the station. Then planting popular trees to hide the cinder blocks from view as well as the sub station. Does this sound like a reasonable approach? I had a picture of the station but there is no upload capability’s on this site.

    Thank you,


    • Edvard
      Mar 16, 2022

      That’s exactly what you should do. Don’t forget to use a sound measuring device before and after building the blocking wall to measure noise decibels.

  5. Katalin Horvath
    Dec 09, 2021

    Dear Mr Csanyi, I live about 7 meters away from a building which is part of an electric substation. My flats back wall is 7 meters from the substations back wall.
    Abou 4 weeks ago we started hearing a drilling noise. It is on and of, but in the evenings it is very difficult. I contacted Western Power (UK), and they had a look today, but the noise has not changed since. There is no change in the noise. I wonder if they made changes to this substation.
    It might be a coincidence but I have a very bad cough for the last 4 weeks without having a cold. Coinciding in time with the noise issue. I wonder if living so close to substation is safe?What is your opinion?
    Thank you.
    Best wishes,

  6. Rebecca Welch
    Feb 07, 2021

    I have lived in the same location for 32 years. About 24 months ago a low bass frequency noise started day and night. I cannot sleep. Sometimes my neighbor hears . In my house, it is constant and people hear it when when they come in. I’ve called and cannot get any help. The sound is driving me insane.

    • Stewart
      Jun 11, 2021

      Hi, Same here. I bought a portable DVD player, but only listen to CDs on it, usually with earphones, but I usually drop off to sleep without. Buy a player with decent sound volume. I found Samsung and Bush to be poor, but Polaroid to be far better than either and probably cheaper. Very often, I just have a CD spinning away on the bed beside me while the DVD player is on ‘Pause’ and this is enough to ignore the hum.

  7. Irene
    Feb 07, 2021

    We have constant humming noise which I am sure is from electrical sub stations. There are two of them within approx half a mile of each other. As the crow flies in a straight line to our house. I can deal with it during the day but night time is very difficult to sleep. Who can I contact in UK to address this?

  8. Chris Wood
    Sep 24, 2020

    Dear Katherine Wyld, the noise can only be mitigated at source, with large/specialist barriers being a common solution. You need to contact your local Council’s Environmental Health Department and speak to an Environmental Health Office or equivalent. If they deem the noise a nuisance, they can serve a notice on the owner to abate it. You can hire an acoustics consultant/engineer to support your case, but at your own expense (likely £1000 or so). I’m intrigued to know where it is, as the distance is quite large. Chris – Anderson Acoustics Ltd.

  9. Katherine Wyld
    Aug 26, 2020

    The low frequency noise that pervades my house 24 hrs a day has been traced to an electric transformer which sits a few metres inside the perimeter fence of the waterworks about 200-300 metres away. This is a rural area and I am on the edge of a tiny hamlet my house is North of the village on the road up to the waterworks. I originally thought the sound was something to do with the waterworks and their sound expert guy came to see me. He could clearly hear the noise and tried switching off all the machines in the works. The sound persisted. He rung me later to tell me about the transformer he had discovered near the perimeter fence. I have now seen it myself, it vibrates and hums. There are two cables coming from it that go straight into the earth and as we know vibrations and sound can travel through the ground. Its definitely the culprit, but what do I do next? Is there a law about this sort of disturbance? I couldn’t sell my house with this impediment. My house is an old cottage sensitively added onto with a beautiful garden, it is a special place, this noise has undermined its magic considerably. I really need to stop this noise. I feel the electric people were very thoughtless to install this transformer so close to dwellings. It has ruined my life here and sleeping at night is hard, ear plugs etc. Hope you can help, Katherine

  10. Georgie Schindler
    Jul 26, 2020

    Hi Micheal, I have a situation similar to what others and yourself describe on this page. Who (Which profession) would be best to assess the situation and then Who would be best to engage for a solution- electrical engineer or acoustic electrician or other. I am in Melbourne, Australia. Hope you are well, Georgie

  11. Devyn Kitchenham
    Apr 26, 2020

    Thank you for your article. I live 5 metres from a substation and there is constant humming with occasional buzzing. I contacted Western Power who provided a microphone device to record noise level. I am waiting their results. Your article helped to understand much and to finally identify what might be making the relentless sound. Thank you again.

  12. James
    Aug 16, 2019

    Sub-stations have to act within noise laws, so why not owners of hot-tubs? The noise is similar or even worse compared to sub-stations, yet any Tom, Dick or Harry can erect these tubs and leave them humming 24/7 knowing only too well the fatigue and stress this inflicts upon their local community.

  13. akula.rama chandrudu
    Dec 13, 2018

    it is very good information to learner and also for A.M.I.E. STUDY CANDIDATES , SO I LIKE SO MUCH, O.K. LOT OF THANKS TO ELECTRICAL ENGINEERING PORTAL COM.

  14. Hiro Shiozawa
    Feb 07, 2018

    Dear Mr. Csanyi

    My name is Hiro and just happened to reach to your website when I was looking for the cause of humming noise in my house.

    I reside in urban area of Orange County, Southern California. Recently So Cal Edison upgraded and installed new transformer in my neighborhood and at around the same time I started hearing low humming noise 24/7 in my house. Sometime it is audible very slightly outside as well. It is very annoying and disturb my sleep.

    I cannot provide data such as frequency of the noise since I don’t have any equipment, however the noise I hear when I stand close to new transformer is very similar to the one I hear in my house. Funny thing is I can hear but my wife cannot. I learned from some website that some can and some cannot hear this sort of noise.

    I don’t know if this fact has something to do with but my house is located on the exact straight line from transformer when you draw that line along the house on the map. My house is about 370ft (110m) away from the transformer and most of (70%) the distance is through open space park.

    You may not expect this sort of comment, however I am desperate to have opinion from expert like you since So Cal Edison is no help. Thank you for your help in advance.


    Hiro Shiozawa

    • Barbara
      Mar 11, 2020

      Wondering if you solved your problem Hiro.
      I am experiencing fluctuations in frequency type noise when my tv is on. I have ruled out the tv and cable companies. It’s driving me nuts.

      • Michel
        Apr 28, 2020

        Hi Hiro,
        I am an acoustical consultant and have worked on noise control of multiple substations. The frequency you are probably hearing is 120Hz; it is a low frequency and it has enough energy to travel several ft. The fact that you have a straight line of sight from your residence to the transformer, the sound travels from the source to the receptor without anything blocking its path. The older the transformer gets, the louder it is going to be. The easiest way is to install a barrier wall close to the transformer so it blocks some of the noise that is coming towards your residence.
        Let me know if you have any questions.
        Michel – Motive Acoustics Inc.

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