What is NVH?
We all know what it is like to be in the car on a hot summer’s day heading to vacation. What could possibly ruin your mood? Exactly! The car’s air conditioner is once again making an annoying squeaking sound and the vehicle noise on the highway is so loud that you can no longer hear the radio. This is exactly what is called NVH (Noise-Vibration-Harshness).
NVH plays an important role in various areas. For example, complaints about cars do noticeably reduce if they perform well in terms of NVH. It is also important for wind turbines, airplanes or even dishwashers to cause as little perceptible noise and vibration as possible. After all, no one wants to sit for hours in a severely vibrating car or hear an annoying squeaking noise when walking past wind turbines.
Whereas vibrations and noise pollution can be measured with measuring devices, harshness is often determined by the remarks of people. Therefore, the term harshness primarily refers to the subjective perception.
Causes and avoidance
The causes of audible or perceptible vibrations are manifold. In cars, the powertrain, tires and engine are primarily responsible for unwanted emissions. At high speeds, however, wind noise can also dominate. The case is similar for wind turbines. While the mechanical components produce most of the noise at low rotational speeds, the rotor blades are the cause at high speeds.
To improve NVH performance, it is essential to identify and eliminate sources of NVH during the engineering process. The fit of components should be as tight as possible, but individual parts should not rub against each other. Bodywork or rotor blades generate little vibration if their design is aerodynamical. The use of materials with high sound absorption (such as fiber-reinforced plastic) can further reduce vibrations.
In general, however, psychological factors do also have a great influence. For example, few people do bother the squeal of a car during emergency braking. Also, wind turbines located near hiking trails have a higher quality requirement than those located in remote areas. By taking these points into account, manufacturers can reduce costs without decreasing the comfort of the products.
A wind power plant may be the source of NVH emission
How to analyze NVH
The analysis of NVH behavior turns out to be difficult. The problem here is that the vibration behavior of components can differ significantly depending on their particular use. Thus, the measurement must always be performed under the exact same conditions. In practice, this is sometimes only possible on special test benches.
Three components are important for measuring vibrations and noises:
- Sensors to capture the signals (including pressure, noise, acceleration or vibration sensors).
- A data acquisition system for recording the sensor data.
- A system for data analysis.
Due to the many contributing factors in NVH analysis, it is necessary that all three components work precisely and reliably. To ensure this, we at DEWETRON have entered into a cooperation with Müller-BBM VibroAkustik Systeme.
Müller-BBM VibroAkustik Systeme is a leading global supplier of systems for the acquisition and analysis of data in the field of acoustics and vibrations. DEWETRON is a manufacturer of high-precision and fully modular measurement equipment. Together, we are able to record and subsequently analyze data of the highest quality. For example, measured electrical quantities such as power and efficiency of electric motors can be directly correlated with NVH data such as housing vibrations and sound radiation. Learn more about our cooperation with Müller-BBM here.
DEWETRON also offers a variety of different measuring devices and modules. You can find all about this on our website. In our webinars and video tutorials we are also happy to explain in more detail what is possible with our products. To stay up to date in the future, you may follow us on Twitter or LinkedIn. We are also regularly active on our YouTube channel.