What is wind noise?
Car wind noise is not difficult for each of us to understand, as long as it involves high-speed relative movement with the air, from airplanes and high-speed trains to air conditioners and electric fans used in our homes, the problem of wind noise cannot be avoided.
It is not easy to attenuate wind noise. Wind noise is directly generated on the body surface, and there is no way to carry out acoustic packaging (it is difficult to eliminate it with sound absorption/sound insulation materials). Especially in recent years, with the popularity of new energy vehicles such as electric vehicles, traditional engines are gradually replaced by motors and hybrid power. These new powertrains have better mute effect, which leads to more and more serious wind noise problems.
Wind noise is not only wide in frequency band, but also strong in intensity, which easily makes passengers feel irritable and tired, and is affected by wind noise for a long time, which will also endanger driving safety.
How to study the problem of wind noise?
In order to study wind noise comprehensively and systematically, it is necessary to carry out experimental tests with the help of wind tunnel, because wind tunnel can meet two necessary conditions for research: first, there is a wind source with stable flow field and accurate and controllable wind speed; Second, interference from other noises can be eliminated.
The test results of this microphone array are finally displayed intuitively in the form of images. Combined with the scanned vehicle model data, engineers can obtain the three-dimensional distribution of noise sources on the body surface.
In addition to acoustic arrays, we can also see several head models and spherical devices in the live broadcast. These sets of equipment are artificial head, spherical array and surface microphone.
During the test, the spherical array will be placed in the cockpit to help engineers find out the sound source distribution and the location of noise leakage in the car. The surface microphone can be attached to the car body surface to measure the pressure pulsation on the car body surface. These three devices are designed to help engineers get the most comprehensive data in wind noise experiments, find problems and improve them.
How to optimize the automobile wind noise?
The optimization of automobile wind noise is a huge systematic project, which mainly starts from two aspects: sound source control and acoustic packaging. Because wind noise is directly generated on the surface of the car, it needs to be controlled from the source of wind noise, that is, modeling design, which has a strong correlation with wind noise. Therefore, in the early stage of product development, the design team will work with the engineering team to polish the design from the details.
In the later development process, more attention will be paid to the design of sealing system and the application of sound insulation and sound absorption materials to further improve the NVH performance of vehicles.
At the beginning of design, engineers usually analyze the aerodynamics of different modeling schemes through CAE simulation, so as to find problems and improve the design. At the same time, it can be further adjusted through the actual test of sludge model. In the live broadcast, the engineer gave two examples to show that modeling has a great influence on wind noise, one is the rearview mirror and the other is the rear of the car.
Although the gap of 0.3dB does not seem obvious from the numerical point of view, the rearview mirror is only partially optimized, and engineers have also optimized countless details on UNI-T. It is this small improvement that will eventually bring about qualitative changes.
As one of UNI-T's iconic designs, the tail wing gives the whole vehicle a hint of science fiction, which not only amazes the engineering team, but also is deeply loved by netizens. But the greater the design innovation, the greater the challenge.
As mentioned above, the single-sided acoustic array has 65,438+068 microphones, while the three-sided array will be used in the test. A * * will collect 504 acoustic signals, and the amount of data is very huge. Just the whole optimization process of UNI-T tail, the amount of data calculation will exceed 1 10,000 CPU hours. If you switch to the latest generation of computer processors on the market, you need to calculate 12 all the time.
To this end, the design team called 4000-core high-performance computing servers, accounting for a quarter of the entire Chang 'an computing cluster, and then compressed the entire computing cycle to 20 days.
After analysis and optimization, UNI-T added a duck tail design at the rear end of the roof, and the spoiler increased the slope. Although it has a hollow shape, when the airflow passes through the rear of the roof, the duck tail will hold up the airflow, and the tail will form an inclined plane to better turn the airflow, so that the trend of airflow hitting the rear window downwards is reduced, and the wind noise is naturally reduced.
Write at the end:
Wind noise is invisible and intangible, but it is an important factor affecting driving quality. In order to reduce the wind noise, a lot of manpower and material resources need to be invested. Through the scene pictures and the stories told by engineers in the test, we can see that every detail on the car body is the crystallization of countless engineers' hard work and sweat. (Editor/car home? Guo Feng)