There is a legend circulating among automotive engineers: There are such a group of ubiquitous people, sometimes seeing them diametrically opposed to the chassis engineers, who are noisy; sometimes they find that they and the auto body engineers have caught on, requiring parts to be repaired, sometimes Again seeing them and the weight engineers rubbing hard foam required increased parts weight. This group of people under the banner of NVH, put forward all kinds of almost demanding requirements, is simply a nightmare for the engineers of the parts. And this group of people who are in trouble is the NVH performance engineer.

NVH, known as the metaphysics in the performance of cars, seems to be an unavoidable thing to say. In this simple science popularization, NVH is in the end. NVH is the English abbreviation for Noise, Vibration, and Harshness. As the name suggests, NVH is the noise and vibration that humans feel when they drive and ride in a vehicle, and the interference caused by these interferences. comfortability.

The three most sensitive perceptions (hearing, tactile, and visual) of a person's five senses are constantly evaluating the vehicle's NVH performance: the ear receives various sounds while the vehicle is driving; the feet can feel the floor of the vehicle. Shaking, the body feels the vibration of the seat, the hand can receive the feedback given by the steering wheel; the eye will also notice the movement of some parts from time to time. Because of this, NVH performance is the most intuitive vehicle performance, and it is also one of the most severe performance complaints from users.

As electric vehicles get more and more popular, major traditional OEMs have released grand plans for electric vehicles, and emerging Internet giants also want to share a share. The electric vehicle is driven by an electric motor. There is no roar of the internal combustion engine and it is very quiet at low speeds. When the speed is less than 20km/h, pedestrians on the roadside will hardly notice that there are electric vehicles in the vicinity.

Therefore, the United States and the European Union have already begun to implement laws and regulations requiring electric vehicles to increase the vehicle sound warning system (AVAS). When the vehicle speed is less than 18 miles (about 29 km) per hour, the vehicle emits an analog sound to alert pedestrians of the presence of electric vehicles. Driving. I believe many people are very happy to see this place. Electric vehicles can not only bring low carbon and environmental protection, but also bring peace and comfort. And it is such a quiet electric car company. It is learned that Gengge has also accumulated a large group of NVH engineers to solve the vehicle noise problem. Why is this?

1. Take the engine noise and come to a motor noise

In general, sound sources are used to classify vehicle noise into four categories: engine noise (or powertrain noise), wind noise, road noise, and exhaust noise. To know that everyone's impression that the quiet state of electric vehicles is limited to low-speed operation, when the speed reaches 40km/h, the noise level of electric vehicles is basically equivalent to the level of traditional internal combustion engine vehicles.

Electric vehicles do not have an exhaust system. Naturally, they do not have to deal with noise in this area. NVH engineers can indeed do less work. The power system with the motor as the core is still a very important noise source. Compared with the internal combustion engine, the operation of the motor is more stable, and the vibration transmitted to the vehicle is much smaller, but the gear noise and electromagnetic noise of the high-speed rotary motor are also Brought much trouble to NVH engineers.

2. Traditional wind noise and road noise still exist and are more prominent

At the same time, wind noise and road noise during the operation of electric vehicles still cause great problems for passengers. When the vehicle speed reaches 60km/h, the roller becomes the main source of noise for passengers. When the speed is higher than 90km/h, wind noise becomes very significant. Wind noise and fetal noise are caused by the interaction between the vehicle and the atmosphere and the ground. Because of the randomness of the air flow and the condition of the road surface, these two types of noise also exhibit great randomness.

3. Entanglement of high-frequency noise

Compared with traditional internal-combustion vehicles, NVH performance engineers face many problems in high-frequency noise (high-speed motor running noise, wind noise, and tire noise) in the development of electric vehicles. To solve high-frequency noise, it is usually necessary to use acoustic material parts, which are commonly known as acoustic packages. However, it is not so simple to add a part to an electric vehicle.

The battery brings a huge additional weight (according to the battery life and battery life, ranging from about 300kg to 500kg), but the laws and regulations require more stringent energy consumption, and the lightweight design pressure in the development of electric vehicles. Huge, any parts that increase the weight of the car body need to undergo repeated optimization design to reduce the total mass of the vehicle, increase the energy efficiency during the operation of the vehicle, and increase the mileage of the vehicle. During the development of the electric vehicle acoustic package, NVH engineers must optimize the design of each acoustic component so that each gram of the component can exert its maximum efficiency and ensure that the vehicle's NVH performance is not affected.

4. Harsh requirements for sound quality

In the era of electric vehicles, another challenge that NVH engineers face is a more esoteric term—sound quality. Just as people's quality of life enhances their quality of life, the customer's NVH performance requirements for vehicles have risen to the level needed for quality. It is often heard that people complain that the loud air-conditioning affects the communication in the car, the sound of the glass goes up and down, and so on.

Under the idle conditions of traffic jams and other conventional cars, the engine is continuously running. The sound of the engine will obscure some of the noise characteristics of the air conditioners and other components during operation. However, when the electric vehicles are in idle conditions, the motor is stopped and the air conditioners are stopped. The operating noise of fans, compressors and other components will be directly revealed. Without the engine's masking effect, NVH engineers have to work hard to cope with the noise and vibration performance of each running part, and use various means to optimize the sound quality of the running noise of the parts.

Based on the impact of noise on the environment, laws and regulations have strict restrictions on vehicle operating noise. Any new vehicle must pass acoustics regulations before it is listed, and only models that meet the national noise standards can be put on the market. The work faced by NVH engineers must not only meet the increasingly stringent quality of users, but also meet the requirements of laws and regulations. The engine is gone, but the NVH engineers do not have much work, even more. In order to create a peaceful in-car world, NVH engineers have also used the power of the utmost.

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