wonderful voice can make people intoxicated, complex sound is distracting, indicating the source of the sound according to good and bad; for a moving car, the wind noise generated by road noise and tire noise will affect car occupant comfort, especially when traveling at high speed when the wind noise will become an important factor affecting vehicle NVH, then how can you effectively reduce wind noise it?
First, we explain what is wind noise? In simple terms, is the car wind noise during running, the shape of the body surface, the contour of the airflow noise generated by the interaction occurs, the greater the speed, the greater the wind noise. So wind noise can be measured out? Of course, look at September 16, Changan UNI-T in China BARI aerodynamics – wind noise experiments conducted acoustic wind tunnel laboratory, let’s look at how the automobile wind noise testing? Changan UNI-T is how to reduce wind noise?
China BARI wind tunnel laboratory is one of the world’s most advanced wind tunnel laboratory, wind tunnel around the walls and top are equipped with sound-absorbing material, flow have acoustic treatment within the channel and adjusting the pressure pulsation, so that background noise is reduced to very low levels. In the experiment the wind speed reaches 140km / h when the ambient noise is only only 58 decibels, is one of the quietest wind tunnel.
Not only that it was the country’s first microphone array mounted on three sides of the wind tunnel laboratory, microphone array, also called ldquo; rdquo ;, acoustic camera on the left and right each of the three sides are equipped with a microphone 168, so that the array can accurately identify a sound source out of the bus. And by the upper sides of the acoustic camera while recording, through matching computer synthesized, the noise source can be obtained in the 3D surface profile of the vehicle body, it is one of the acoustic measuring equipment currently the most advanced, but also very accurate, site after test landing sound even two paper clips can be displayed on the monitor screen.
Some wind noise tester foreman, spherical array, microphones surface; artificial head mainly when collecting people feel real car noise in the test, will be placed on the front row driver and passenger seat. Position of the artificial head mounted acoustic binauralSensors, so that when recording sound may simulate the effects of shoulder, head and ear and other parts of the sound field, a playback audio signal is closer to an actual human ear to hear. Spherical array in the test will be placed inside the cockpit to help identify the source of the sound inside the car as well as the distribution of noise leak location. A microphone attached to the surface of the body surface, the pressure pulsations acting on the measuring body surface. Three devices are designed to assist the most comprehensive data in wind noise experiments to identify problems and make improvements.
Arrangements start testing instrument, you first need to adjust the speed needed to test the speed, doing wind noise testing, they usually wind speed will set 80mdash; 140km / h per hour, the wind speed setting live 120km / h, and artificial acoustic camera head usually about 30 seconds of data collection, the computer will complete the acquisition of raw data for further processing, and to obtain the required information.
one surface an array of 168 microphones, three arrays will be a total sound collection signal 504 channels, the amount of data is very large, the processing of these data may take some time. Artificial head but only two-channel signal acquisition, so that the processing time will be much faster.
can be seen in different wind speeds, wind noise UNI-T test at different frequency bands are not the same, we can estimate the noise source spectrum by the noise screen the size and feel different frequency bands gives ear is different. On the whole, UNI-T wind noise test results in a relatively good level in the industry. So Chang UNI-T is designed to reduce wind noise how to optimize it?
UNI-T at the beginning of the design, modeling programs have to analyze the different aerodynamic quality by CAE simulation to find the problem to improve the design, and the actual test is performed by modeling clay model adjustments and further .
in order to optimize the rear-view mirror, for example, were only mirrors wind noise optimization, modeling it involves multiple departments, regulations, CAE and product, whether good-looking shape , vision meets the regulatory requirements, whether the final adjustment of wind noise can complete complianceRequires collaboration and cooperation with various departments, a tiny change required the joint efforts of countless people behind. By optimizing the rearview mirror, the overall sound pressure level at the driver’s ear will be reduced 0.3dB (A), enough to appear Chang CFD technical strength. Such details of the optimization on the myriad of UNI-T, all of this 0.3dB (A), add up, eventually produce a qualitative change.
As one of the logo design of UNI-T, UNI-T tail design is very special. Such advanced design, also pose a particular challenge to the CFD team. After all, from an aerodynamic point of view, tend to make all the cars are designed to shape a way, but this is clearly not what consumers want to see, therefore, aerodynamics’s mission is to make each form different design, are able to have a good aerodynamic performance.
Since the tail using a hollow design, the air flow will impact the roof through the holes and the V-shaped channel downwardly to the rear window, formed of a large wind noise. The first time I saw this design, CFD team held an emergency meeting, has repeatedly demonstrated the feasibility and risks, and calls the 4000 nuclear simulation resources, calculating the amount of more than 1 million CPU hours. If the change in the market of high-performance personal computer processors, computing need to keep more than 12 years, and the core HPC server 4000, the entire compression calculation cycle to 20 days. Before and after doing the calculation over 60 optimization, and ultimately find more than 20 active programs, dramatically reducing the wind noise generated by the tail.
Conclusion: continuous optimization through CFD team Chang, UNI-T also been reduced wind noise, ultimately UNI-T at 120 km / h of wind speed, wind noise is still achieved good test scores. So behind the UNI-T from the market since its excellent sales performance, its excellent product strength is its strong technical strength.