Cars can also actively reduce noise, do you believe it?

The most headache in daily driving is noise, which affects the driving experience. Now, mid-to-high-end headphones have active noise reduction functions, and the active noise reduction function of headphones is very mature. The most influential brands in this regard are BOSE and SONY.

Active noise reduction functions are also used in cars now. After more than 10 years of development, BOSE’s ANC active noise reduction technology for vehicles has become quite mature. The first mass-produced model using ANC noise reduction technology is the Nissan Fengya and Infiniti M series. Today I will share a familiar and unfamiliar technology-ANC active noise reduction.

What is ANC technology
The principle of ANC (Active Noise Control) active noise reduction technology is that sound waves with the same amplitude and opposite to the noise source (phase difference of 180°) are emitted through the silencing speaker, and the two sound waves are superimposed to achieve the purpose of noise elimination. A common configuration using ANC technology is 5 speakers on the car and a noise sensor on the roof. The loudspeaker can be an entertainment player or a muffler for noise in the car. The noise sensor is mainly used for real-time monitoring of the noise in the car, and the correction coefficient is used for calculation and real-time feedback.

In the 1970s, the founder Dr. BOSE was on a plane from Europe to Boston and found that the noise of the aircraft's engine had wiped out the interest in listening to music, which inspired the research on noise reduction technology. The first headset was designed for pilots, then it was applied to civilian headsets and then to cars. The difference between the active noise reduction of the car and the earphone is that the active noise reduction of the earphone is based on the excellent passive noise reduction, and the active noise reduction of the car is a configuration that compensates for the lack of passive noise reduction.

Sources of car noise
Engine noise
Engine noise is the main noise source of automobiles. With the increase of engine speed, the high-speed movement of pistons forms a strong impact of the piston on the cylinder wall. It is inevitable that a large amount of noise will be generated. There are also noises generated during intake and exhaust, and One is the noise from abnormal combustion (deflagration and surface ignition) of the engine. Dealing with this kind of noise is very simple, the owner only needs to paste a high-grade attracting foam material on the engine cover.

Wind noise
All car owners who have been on a high-speed know that once the car is running at a high speed, the noise is particularly loud, especially the sound of wind entering through the door crack, which is uncomfortable. In fact, the way to deal with this noise is to install a sealing strip on the side of the door, which can ensure sound insulation and airtightness.

Tire noise
The tire is the only contact surface between the car and the ground. When the tire is rolling, the pattern causes air disturbance and the vibration of the carcass to cause noise. It is difficult to feel the tire noise at low speeds, and the tire noise will be more obvious at high speeds. There is obviously no completely silent tires, but through the design of patterns, structures, and materials, the noise of the tires can be reduced, and "silent tires" have appeared.