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Transmission Noise

Present, Potentially Affected

The Environmental Protection Agency (EPA) has set federal noise standards pursuant to the Noise Control Act (42 USC §4901-4918 et seq. 1972) to: • Conduct noise control research; • Limit industry noise impacts; and • Provide information to the public about noise abatement technology.


Noise surveys are typically conducted before the project construction to measure the existing decibels from background noise at the site. This determines how much noise the project can produce at one time. An acoustic engineer typically monitors the sound impacts throughout the project.

Noise Impacts & Mitigation

A transmission line’s noise impacts range from minor to major, depending on power stability, security, and construction hours of operation. The biggest impact is incurred by an error called “critical disruptive voltage”, or the “corona effect”. When the power threshold exceeds its maximum voltage capacity, the field strength increases and the air surrounding it becomes stressed. The ions separate and cause atmospheric conducting. This results in the line producing a purple or blue luminescent glow, ozone gas discharge, and a buzzing sound. These discharges naturally occur in high-voltage systems if the electric field strength is not limited or the power lines are not equip for the air’s moisture levels.

Reduce construction, traffic, and operation noise impacts with the following mitigation measures:


  • Implement a training program for employees to learn about the health risks associated with prolonged exposure to abrasive noise.
  • Safety training overviews may include how to wear personal protective ear wear and how to reduce noise while working.


  • Surround the proposed substation site with a buffer to mitigate construction noise disturbances to area residents.
  • Design power lines to minimize noise from energized conductors.
  • Equip internal combustion engines with mufflers, engine shrouds, and spark arresters.
  • Surround generators or pumps with temporary sound walls or acoustic blankets to shield adjacent sensitive receptors.
  • Decrease vehicle idle time to mitigate long periods of uninterrupted noise. Large diesel-powered vehicles may be exempt, as they require idling warm-up and perform repetitive construction tasks.
  • Notify landowners located along the corridor prior to construction activities, including blasting.
  • Require personal protective gear such as hearing protection and gloves.
  • Set up a toll-free telephone number to receive and resolve construction noise complaints from area residents. Log and address each concern.

Corona Effect

  • To mitigate critical breakdown voltage interferences, increase conductor diameters and keep them dirt and debris free.
  • Use hardware that reduces audible noise, and radio and TV interference. To avoid sparking, maintain tension on all insulator assemblies. This assures positive contact between insulators.
  • Avoid scratching or nicking the conductor surface, which trigger corona effects.
  • Keep dirt and debris off of the conductor.
  • Frequently patrol the transmission line corridor to repair or replace damaged insulators or other line materials that could cause interference.

Hours of Operation

  • Each contract and leasing agreement states whether 24 hour operation is allowed. In most cases, 7am-7pm incurs the least amount of impacts to area residents.
  • If any noise complaints occur, additional professional consulting assesses which mitigation measures to take to reduce noise impacts.
  • All site traffic must comply with the hours of operation and oversized vehicle arrival and departure will be coordinated with the local traffic schedules.