Wind farms are quickly becoming a leading alternative among the natural energies. In some cases though, wind turbines have created the problem of noise and low-frequency sounds.
INC is highly experienced in investigating and studying noise and low-frequency sound from wind turbines. With detailed understanding of how noise and low-frequency sounds are generated, propagated and emitted from wind turbines, INC ensures survey and estimation to determine the features of the wind turbine noise.

We Meet the Following Demands

> Noise source identification of wind turbine noise

Measuring wind turbine noise and low-frequency sound comes with difficulties different from those in measuring noise in common machinery. Wind turbines operate with natural wind force varying in intensity and direction from moment to moment. In addition, wind noise must be prevented as the microphone itself is exposed to wind.

The aerodynamic sound can be characterized as follows:

• Relatively gentle frequency (no conspicuous peak components).
• Sharp directionality. Due to a combination of blade rotation and direction, the sound levels around the wind turbine, known as swishing or swashing, will fluctuate periodically corresponding to blade passage.
• Sound pressure level rises with operation speed. There should be no remarkable rise any longer when a certain operation speed (rated rotational speed; approx. 20 rpm for large wind turbines) is reached.

Mechanical noise comes from the devices housed in wind turbines, such as speed-up gears, generating elements and cooling fans. The vibration of speed-up gears may propagate to the tower and cause outside noise, or structure-borne noise (see the figure below).

Mechanical noises can be characterized as follows:

• They contain peak frequency components defined by factors such as specific rotational speed of each device and number of gear teeth (predominant noise). This makes them more noticeable to ears than aerodynamic sound.
• These differ in level and frequency from turbine type to type.

INC’s Technology for Measuring Wind Turbine Noise and Low-Frequency Sound

Measuring wind turbine noise and low-frequency sound comes with difficulties different from those in measuring noise in common machinery. Wind turbines operate with natural wind force varying in intensity and direction from moment to moment. In addition, wind noise must be prevented as the microphone itself is exposed to wind.
INC minimizes these potential influences to offer a more accurate and efficient measuring method:

• Efficient measurement for long period collection of data under various wind conditions
• Special wind protection (Kaze Konah-kun)
• Measurement for noise source identification
• Verification of noise propagation by concurrent measuring on both generating and receiving ends
• Measurement based on JIS C 1400-11

Noise Estimation and Simulation for Wind Farms and Turbines

The potential impact of noise in surrounding areas must be determined in the planning phase for wind power generation facilities and wind farms. Accurate noise estimation and simulation are important for this purpose.
INC combines its storied experience in estimation of noise propagation for plants and production facilities with its knowledge on wind turbine noises to offer highly accurate noise estimates and simulations.