Introduction to related knowledge of anemometer
When measuring the noise meter, the instrument should select the correct gear according to the situation. Hold both sides of the noise meter flat with both hands, and the microphone points to the sound source to be measured. Extension cables and extension rods can also be used to reduce the impact of the appearance of the noise meter and the human body on the measurement. . The position of the microphone should be determined according to relevant regulations.
The sound level meter can be connected with an external filter and recorder to perform spectrum analysis on the noise. The domestic ND2 precision sound level meter is equipped with an octave page filter, which is easy to carry to the scene and do spectrum analysis. Process calibrator Temperature calibrator Pressure calibrator Loop calibrator Calibration buffer Clamp calibrator Oscilloscope calibrator Noise meter calibrator Current calibrator Multifunctional calibrator Humidity calibrator ph calibrator
With the rapid development of economic level and urbanization, cars are rapidly popularized. In order to achieve the coexistence of humans and cars and reduce noise pollution and harm, it is necessary to protect the environment and implement reasonable measures to reduce noise. From the perspective of future development trends, in order to ensure the impact of car noise on the environment, the restrictions on driving noise will be enforced; the noise will also be reduced by changing the traffic flow to change the regional traffic pattern; in addition, the research and development of electric vehicles, hybrid Power vehicles are also an effective measure to reduce noise; in terms of road construction, improvements in road shape, structural pavement materials, etc. will also play a positive role. The control of the noise meter is specific to the technical level, and is divided into two types: mechanical principle noise control and acoustic principle noise control: noise control measures based on mechanical principles:
Improve the structure of mechanical equipment and apply new materials to reduce noise. With the development of material science and technology, various new materials emerge as the times require, and it has become a reality to use some alloys with high internal friction, high damping, and high-strength plastics to produce machine parts. For example, high-strength plastic parts are often used in automobile production. For fans, different forms of blades produce different noises. Choosing the best blade shape can reduce noise. For example, changing the fan blade from a straight blade to a curved shape, or reducing the length of the blade can reduce noise. The noise generated by the general gear transmission is relatively large, up to 90dB. If helical gears or helical gears are used instead, the coincidence coefficient during meshing is large, and the noise can be reduced by 3 to 16dB. If the belt drive is used to replace the general gear rotation, the noise can be reduced by about 15dB because the belt can reduce vibration and damping. For gear-type transmissions, noise can also be reduced by reducing the linear velocity of the gears and selecting an appropriate transmission ratio. Experiments have shown that if the linear speed of the gear is reduced by half, the noise will be reduced by about 6dB.
Improve the machining accuracy and assembly quality of parts. The improvement of the processing precision of the parts reduces the friction between the parts as much as possible, thereby reducing the noise. Improving the quality of assembly, reducing eccentric vibration, and increasing the rigidity of the casing can all reduce the noise of machinery and equipment. For bearings, if the machining accuracy of the rollers is increased by one level, the noise of the bearings can be reduced by 10dB. Noise control based on mechanical principles mainly depends on the research and development, production and assembly of automobiles, and is generally a noise reduction measure taken before the vehicle leaves the factory. In the later use and maintenance process, avoiding no-load and overloading of mechanical equipment and vehicles, and choosing good lubricating grease can reduce noise.
Noise control measures based on acoustic principles: In addition to the above methods to reduce noise, acoustic control methods can also be used to reduce noise, mainly including sound absorption, sound insulation, shock absorption, sealing, etc. For automotive noise control, since the noise-causing components such as the engine, exhaust pipe, and tires are finalized when the vehicle leaves the factory, the design level and assembly process of each component determine the size of the noise, and also reflect a The technical level and technological content of the car. Tranquil car sound insulation is mainly researched and developed from the control of the barrier transmission path.
