Otis Singleton
Wind turbines are a great source of clean, renewable energy, but some have complained about the noise they produce for residents living within a mile of the blades. The sound a wind turbine makes is associated with the rotation of mechanical and electrical equipment as it produces electricity. The noise varies with the atmosphere and terrain, and the quietest place to stand is often right underneath it. Modern small wind turbines have better insulation, lower rotation speeds, and more efficient blades, making them much quieter than older models. The sound they emit is barely discernible from ambient noise, and sound from traffic, rustling trees, and other sources often masks the dull, low, white noise sounds a small turbine makes.
| Characteristics | Values |
|---|---|
| Sound pressure level at 300 meters away | 35–45 dB |
| Sound pressure level at 500 meters away | 38 dB |
| Comparison to background noise | In most places, background noise ranges from 40 to 45 dB, meaning that a turbine’s noise would be masked by it. |
| Comparison to average household appliances | A typical refrigerator produces 50 dB of noise, while most run at around 40 dB. An average air conditioner can reach 50 dB. |
| Effect on human health | A 2012 review of global peer-reviewed scientific data found that wind turbine noise does not pose a risk of hearing loss and has no direct impact on physical human health. |
| Effect on psychological health | Constant low-level sound from wind turbines has been linked to adverse psychological effects, including depression and exhaustion. |
| Effect on wildlife | Underwater noise from offshore wind turbines has been studied for its potential impact on marine mammals and coastal cetaceans. |
| Factors influencing sound | Wind speed, height, and distance from the source. |
| Types of sounds produced | Broadband sound (humming, whooshing, or swishing), infrasonic sound (felt as vibrations rather than heard), impulsive sound (brief and sudden), tonal sound (caused by mechanical pieces like shafts, generators, and gears), mechanical sound, aerodynamic sound, low-frequency sound, and inaudible vibrations (infrasound). |
| Strategies to mitigate sound | Modern turbines use suppression and isolation of vibration and fault detection. Manufacturers have also invested in new materials and designs to minimize sound. |
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What You'll Learn
- Wind turbine noise varies with the atmosphere and terrain
- Modern small wind turbines are much quieter than older models
- Mechanical and electrical equipment produce sound as they generate electricity
- Wind turbine noise can be mitigated with suppression and isolation of vibrations
- Wind turbine noise is similar to white noise
Wind turbine noise varies with the atmosphere and terrain
The sound produced by wind turbines can be divided into four types: broadband sound, infrasonic sound, impulsive sound, and tonal sound. Broadband sound is a combination of sound waves with different frequencies and no distinct pitch, often described as a hum or a whoosh. This type of sound is similar to the noise made by a fan or ocean waves and is often called white noise. Infrasonic sound has a frequency lower than 20 hertz, which is the limit of the audible range for humans. It is always present in the environment and is typically felt as vibrations rather than heard. However, it can sometimes cause structural vibrations, such as window rattling. Impulsive sound is brief and sudden, typically lasting a few seconds or less. It is generated when disturbed airflow interacts with turbine blades, resulting in swishing noises. The volume of impulsive sounds can vary, and they can be louder or quieter depending on the amplitude. Tonal sound is caused by the mechanical components of the turbine, such as shafts, generators, and gears operating at a natural frequency. This type of sound can have a distinct pitch and usually fades in and out rather than starting or ending abruptly.
The noise produced by wind turbines has been a topic of research and discussion, with developers working to address potential sound issues and comply with applicable sound-level regulations. Modern commercial turbines have blades designed to be upwind of the tower, which helps mitigate low-frequency and impulsive sound. Additionally, changes to blade designs and the use of sound-dampening buffer pads have contributed to reducing the overall noise emitted by wind turbines.
According to measurements, the sound emitted by utility-scale wind turbines falls within the range of 35-45 dB when heard from 300 meters away, which is the closest distance a wind turbine is typically placed to a home or building. This noise level is comparable to the sound of a refrigerator and is significantly lower than the noise produced by city car traffic, which averages around 70 dB. Furthermore, a 2012 review of global scientific data and independent studies concluded that wind turbine noise does not pose a risk of hearing loss or have any direct impact on physical human health.
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Modern small wind turbines are much quieter than older models
The noise generated by wind turbines depends on several factors, including the design, the speed of rotation, and the distance from the source. Turbine noise is also influenced by the atmosphere and terrain, with the wind carrying sounds further. While wind turbines have been associated with noise complaints and potential health concerns, modern small wind turbines are designed to be much quieter than older models.
Older wind turbine designs, particularly those with the rotor downwind of the tower, tend to generate more noise due to localized disturbances in the wind passing around the tower. These designs are less common today. Modern small wind turbines have improved features such as better insulation, lower rotation speeds, and more efficient blades, which contribute to reduced noise levels.
The sound produced by modern small wind turbines is often described as a dull, low "white noise," similar to a running fan or ocean waves. This type of broadband sound has no distinct pitch and blends into the ambient noise of the environment, making it difficult to discern. The noise emitted by these turbines is typically only slightly above the ambient wind noise, usually less than 6 decibels (dB).
To address noise concerns, manufacturers have invested in new materials and designs to minimize sound. For example, the Eco Whisper Turbine, designed for residential use, claims to be quieter and more efficient than traditional three-blade turbines. Additionally, modern commercial turbines are designed with blades upwind of the tower, which helps mitigate low-frequency and impulsive sound.
While modern small wind turbines are quieter, certain events or circumstances can temporarily increase their audibility, such as severe storms or utility outages. During these occurrences, ambient sound levels also tend to rise. Overall, modern small wind turbines have significantly reduced noise levels compared to older models, and researchers continue to work on evaluating and mitigating wind turbine noise.
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Mechanical and electrical equipment produce sound as they generate electricity
Wind turbines, for example, produce different types of sound depending on their different parts. Broadband sound, a combination of sound waves with different frequencies and no distinct pitch, can be described as a humming, whooshing, or swishing sound, like a running fan or ocean waves. Impulsive sounds are brief and sudden and can be generated when disturbed airflow interacts with turbine blades, making swishing noises. Aerodynamic noise, associated with the movement of the blades through the air, is the dominant source of audible noise from wind turbines.
Modern wind turbines use strategies to mitigate mechanical sounds, including suppression and isolation of vibration and fault detection. These strategies render mechanical noise inaudible above the aerodynamic noise of the blades or the ambient noise in the environment, except during the brief application of mechanical brakes.
Electricity flowing through wires and devices as a current often causes vibrations or mechanical reactions that humans can perceive as sound. For example, a buzzing or humming noise near an outlet or appliance may indicate an overloaded circuit or faulty electrical component. In quiet environments, even faint electrical noises can stand out. Some individuals have more sensitive hearing and can detect subtle vibrations or high-frequency sounds that others cannot.
The sound of electricity is also determined by its frequency, which is the measurement of multiple occurrences of events, such as sound waves from vibrations, over a period of time. Electric currents can affect the internal structure of transformers, causing vibrations that create a buzzy tone referred to as "mains hum." This hum is ever-present, although not always perceptible to the human ear. On cold, misty mornings, power lines, pylons, and transformers sometimes produce a crackling sound as electricity moves through them.
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Wind turbine noise can be mitigated with suppression and isolation of vibrations
The sound of an electric turbine is associated with the rotation of mechanical and electrical equipment as it produces electricity. While research suggests that wind turbine noise does not pose a risk to human health, it can be mitigated with suppression and isolation of vibrations.
Wind turbines create sound through various mechanisms, including blade-passage phenomena, mechanical drivetrain components, and tonal sounds from the mechanical pieces that turn blade rotation into power. The noise varies with the atmosphere and terrain, and different parts of a wind turbine make different types of sounds. For instance, broadband sound, which is a combination of sound waves with different frequencies, can be described as a humming or whooshing sound, while impulsive sound is brief and sudden, generated when disturbed airflow interacts with turbine blades. Tonal sounds, on the other hand, can have a distinct pitch and are caused by mechanical pieces such as shafts, generators, and gears.
To address wind turbine noise, strategies such as suppression and isolation of vibrations are employed. Vibration damping techniques are crucial for wind turbine noise control. These techniques aim to isolate and dampen multi-frequency vibrations without compromising the structural integrity and power generation efficiency of the turbine system. One such method is the use of a passive aerodynamic damping structure for wind turbine blades, which suppresses blade vibrations under unstable airflow conditions. This structure has lobes and a rotary mechanism mounted at the blade tip, with the lobes generating aerodynamic forces that dampen the vibrations.
Another approach is the use of a resonance control device, which consists of a housing with sound-absorbing material, a vibration sensor, and a rotating block. The vibration sensor detects turbine vibrations and transmits a signal to a steering gear, which adjusts the fan blade angle to counteract and prevent resonance. Additionally, the use of a real-time vibration control system allows for the active mitigation of turbine vibrations during operation. By utilizing a movable mass block, the system can alter the natural frequency of the turbine, preventing resonance and reducing vibration amplitudes.
Furthermore, noise reduction in wind turbines can be achieved through various techniques, including the use of noise-reducing blades, active control systems, and offshore turbine yawing suppression devices. Designing low-noise turbines involves employing analytical tools to accurately predict and diagnose acoustic performance, reducing retrofit costs and certification risks. For instance, serrated trailing edge designs, porous blade covers, and pitch optimization strategies can help minimize both aerodynamic noise and mechanical vibrations.
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Wind turbine noise is similar to white noise
The sound of an electric turbine is associated with the rotation of mechanical and electrical equipment as it produces electricity. Wind turbines 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. This is known as aerodynamic noise and is the dominant source of audible noise from wind turbines.
Wind turbine noise varies with the atmosphere and terrain. The quietest place to stand near a turbine is often right underneath it. The noise is broadcast outward and can be more troublesome at night when the air near the ground is still and the air at hub height is in motion.
Wind turbine noise, or broadband sound, is a combination of sound waves with different frequencies that have no distinct pitch. It can be described as a humming, whooshing, or swishing sound, like the running of a fan or ocean waves. This type of sound is often called white noise.
Different parts of a wind turbine make different types of sounds. For example, impulsive sound starts and stops suddenly and is typically brief, lasting a few seconds or less. It is generated when disturbed airflow interacts with turbine blades, making swishing noises. Tonal sound, on the other hand, is caused by the mechanical pieces of a turbine that turn blade rotation into power, such as shafts, generators, and gears operating at a natural frequency. Tonal sounds can have a distinct pitch, such as a musical note, and fade in and out instead of starting or ending abruptly.
While wind turbines do create noise, modern residential wind turbines create sound that is only slightly above the ambient wind noise (less than 6 decibels). On average, land-based, utility-scale wind turbines produce sounds in the range of 35-45 dB when heard from 300 meters away, which is the closest distance a wind turbine is typically placed to a home or building. This means they are no louder than a typical refrigerator and create far less noise pollution than average city car traffic.
Research has also shown that sound from wind turbines does not pose a risk of hearing loss and has no direct impact on physical human health. However, some studies have found an association between wind turbine noise exposure and self-reported sleep disturbance, annoyance, and possibly even psychological distress.
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Frequently asked questions
Electric turbines create a sound that is slightly above the ambient wind noise. The noise is usually described as a dull, low humming, whooshing, or swishing sound, like a running fan or ocean waves. This is known as broadband sound or white noise.
On average, large wind turbines produce sounds that fall in the range of 35-45 dB when heard from 300 meters away. That means they are no louder than a typical refrigerator (50 dB) and create less noise pollution than average city car traffic (70 dB).
The sound of an electric turbine depends on the atmosphere and terrain. The noise is broadcast outward and can be more noticeable at night when the air near the ground is still. The sound also varies with the different parts of the turbine, with the blades creating aerodynamic noise and the mechanical pieces creating tonal sound.
According to a 2012 review of global scientific data, the sound from wind turbines does not pose a risk of hearing loss and has no direct impact on physical health. However, constant low-level sound from any source can have unhealthy psychological effects, such as depression and exhaustion.
