When car consumers buy vehicles, in addition to considering the performance of the car, such as power, handling, and safety, they also consider the comfort of the vehicle. Noise, vibration and harshness (NVH) has become an increasingly important factor for consumers in buying a car. A car with a high NVH rating performance will provide a more comfortable ride. In the design and development of new vehicles, car manufacturers need to evaluate and develop new models with higher performance.
What is NVH technology?
NVH is a general term for three items: Noise, Vibration, and Harshness. A low NVH motor powered vehicle is one with a measured acceleration noise of <67dB (without soundproof cover), in line with CNS 5799 noise test regulations. The maximum noise level of an electric vehicle in the driver's right ear is expected to be less than 68dB at 0~80 kph.
What is NVH testing?
NVH testing is done to detect and indicate the source of Noise, Vibration, and Harshness. The level of vibration and noise have always been factors consumers consider when buying vehicles, and are important factors in determining the added value of a vehicle.
NVH technology features:
- Noise: Unpleasant, loud sounds.
- Vibration: In vehicle manufacturing, it is not possible to maintain complete uniformity of materials and construction. Because the accuracy of manufacturing is limited, and there will always be some vibration in the finished vehicle. Wear after use will also lead to further vibration of moving parts of the vehicle.
- Roughness: The combined discomfort caused by the vibration and noise generated by the road surface, the engine, and the vehicle body during the running of the vehicle.
Technical overview: The low NVH of electric drive motors in electric vehicles has been achieved by the increased efficiency in design of electric motors. The measured acceleration noise of electric vehicles is <67dB (without soundproof cover), in line with CNS 5799 Noise test regulations. Maximum driver right ear noise of electric vehicles at 0~80 kph is 68dB. Technical features: High efficiency and low NVH drive motors, with 210 Nm torque output and maximum speed of 8000 rpm, provide a maximum efficiency of 96 %. High-efficiency performance can be maintained over a wide range of torque and speed operating conditions. Because NVH for electric vehicles have been verified to comply with CNS regulations, they are suitable for commercial vehicles as well as passenger cars.
Why is NVH testing important?
NVH testing can indicate inadequacies of the vehicle so that overall performance and comfort of the occupants can be improved and enhanced. While driving, the driver and passengers can feel whether the vehicle is comfortable or not. Vehicles with good performance have low vibration and noise and are quiet and comfortable to drive, so are less prone to causing fatigue over long distances. This improved performance is achieved through rigorous design, manufacturing, and testing.
NVH application range:
NVH evaluation is applied to all kinds of general sedans, passenger cars, commercial vehicles, and urban vehicles with power requirements between 50 and 70 kW. NVH evaluation is used to locate sources of vibration and noise, and optimize the design and performance of the gearbox, magnetic brake, power system, and engine of electric and hybrid electric vehicles.
NVH test items:
- Idle Test: When the vehicle is started, the idling NVH is the first NVH felt by the occupants. Testing is performed at the idle speed to judge the idling conditions of the vehicle with the transmission in the P, N, and D gear positions.
- Acceleration Test: The driver will accelerate the vehicle to within the legal speed limit. The acceleration NVH will evaluate what can be felt by the occupants of the vehicle during acceleration.
- Constant Speed Test: As the vehicle driving at a constant speed is the condition experienced for the longest period of time, the constant speed NVH testing is important. The constant speed test evaluates the NVH the occupants of the vehicle experience under constant speed conditions over a range of varying driving speeds.
- Coast Test: As the vehicle is not always under driving force from the engine, but is also often under coasting conditions, or is slowing down, a coasting test is used to evaluate the vibration and noise experienced by the occupants of the vehicle under these conditions.
- Wind Noise Test: While driving on a highway at high speeds (>100kmh), wind shear on the outside of the vehicle will generate sounds which are perceived as noise. A wind noise test is used to evaluate the source of the noise and what impact the wind noise will have on the occupants of the vehicle.