Wind Turbine Sound
Do Wind Turbines Make Sound?
Operating wind turbines can create several types of sounds, including a mechanical hum produced by the generator and a “whooshing” noise produced by the blades moving through the air. The presence of wind turbine sound can depend on atmospheric conditions, including air flow patterns and turbulence, as well as a person’s ability to perceive the sound, which varies based on site-specific topography (the shape of the terrain) and the presence of other nearby sources of sound, manmade or otherwise.
Researchers continually measure wind turbine sounds and advance technologies to reduce them.
Types of Wind Turbine Sounds
Different parts of a wind turbine make different types of sound, including:
- Broadband sound is a combination of sound waves with different frequencies that has no distinct pitch and could be described as a humming, whooshing, or swishing sound, like the running of a fan or ocean waves. Broadband sound is often called white noise.
- Infrasonic sound is always present in the environment at frequencies lower than the limit of audible range (20 hertz). There can be an infrasound component in flowing water or atmospheric turbulence, typically felt, if noticed at all (as vibrations or pressure waves), rather than being heard. Sometimes, however, it can cause structural vibration, such as window rattling.
- Impulsive sound starts and stops suddenly and is typically brief (a few seconds or less) in duration. Impulsive sounds can be generated when disturbed airflow interacts with turbine blades, making swishing noises. Impulsive sounds can vary in volume (amplitude) over time. Examples of impulsive sounds include a dog barking or a dropped book landing on the floor.
- Tonal sound can be caused by the mechanical pieces of a turbine that turn blade rotation into power, like shafts, generators, and gears operating at natural frequency. Wind interacting with the turbine also falls under this category, such as unstable airflow passing over holes or slits in the structure or interacting with a blade’s surface. Tonal sounds can have a distinct pitch, such as a music note, and fade in and out instead of starting or ending abruptly.
Because it is difficult to recreate in a home or lab sound levels that may be heard at a proposed wind energy project site, people are strongly encouraged to visit an operating wind farm to better understand potential sound impacts.
Are Wind Turbine Sounds Noisy or Loud?
Most modern [residential](/markets/distributed] (small- to medium-sized) wind turbines create sound that is only slightly above the ambient wind noise (less than 6 decibels [dB]). Under most wind conditions, a small wind turbine that meets certification requirements does not create a significant amount of noise.
On average, land-based, utility-scale (large) wind turbines produce sounds that fall in the range of 35–45 dB when heard from 300 meters away (the closest distance a wind turbine is typically placed to a home or building). That means they are no louder than a typical refrigerator (50 dB) and create far less noise pollution than average city car traffic (70 dB).
When it comes to offshore wind energy, underwater noise from various offshore wind turbines is at least 10–20 dB lower than ship noise in the same frequency range, according to a 2020 Danish study. Additionally, offshore wind turbines are typically situated far enough from land that communities on shore will likely not hear them.
Does Wind Turbine Noise Impact Human Health?
Although research to develop sound mitigation techniques is ongoing, a 2012 review of global peer-reviewed scientific data and independent studies came to the conclusion that sound from wind power plants does not pose a risk of hearing loss and has no direct impact on physical human health.
A webinar from 2010 references studies on different sound levels that echo the same findings: the health of study participants was unaffected by sounds such as those from wind turbines.
Read more about the potential health and safety concerns of wind energy projects.
How Can We Reduce Wind Turbine Noise?
Many stages in the siting, development, and deployment of renewable wind energy technology consider sound mitigation.
Researchers evaluate wind turbine noises, help manufacturers design and build quieter turbines, and work to model noise at wind turbines based on observations. Researchers continue to evaluate and identify ways to reduce noise when installing offshore wind energy projects as well as work with the Bureau of Ocean Energy Management to establish limits.
Modern commercial turbines are designed so that the blades are upwind of the tower, which mitigates low-frequency and impulsive sound. Other parts of a turbine design can also make turbines quieter. For example, changing the shape of wind turbine blades can make them more aerodynamic, allowing wind to pass through at a reduced volume or different frequency. Wind turbine gearboxes and generators can also be soundproofed using sound-dampening buffer pads.
When planning and installing wind farms, developers use several methods to manage or mitigate potential wind turbine noise or compensate for its impact. Developers are typically required by local ordinances to address potential sound issues in the permitting process and must demonstrate that the project will comply with the applicable sound-level regulations. In most cases, acoustic modeling is performed before and after a wind energy project is constructed to ensure that residents in proximity of a wind turbine experience sound below the appropriate thresholds.
Other methods include:
- Understanding and documenting potential turbine noise during the project development stage
- Maximizing the distance between wind turbines and nearby inhabited buildings or property lines
- Conducting studies to ensure that turbine sounds and background noise do not surpass the Environmental Protection Agency sound guideline of 55 decibels for outdoor sound
- Creating “sound easements” on adjacent property that give the developer the right to generate sound carrying over onto that property
- Sharing of some portion of landowner royalty payments with affected neighboring landowners.
Operators of working wind farms typically communicate with local communities to reduce any potential noise pollution. For example, they can change turbine operating modes depending on wind conditions to reduce noise.