Abnormal Noise Sources Identification And Control Of The Wall-mounted Air-conditioner

The noise control of air conditioner, which is an important component to reinforce the competition ability, has been paid more and more attention. When the air conditioner is working, the abnormal noise will have an obviously negative influence on the consumer. Because of this, only when the abnormal noise sources of the air conditioner's Indoor Unit are identified accurately and controlled effectively, could we improve the product's quality more effectively.At the present day the study at home and abroad indicate that the principal noise sources of different kinds of air conditioners are three below: fans and fan's motor; the compressor; vibration of air duct, fixed Facilities and pipes which the refrigerant get through. So it is important to study the noise sources of air conditioner's fans and the compressor first for the abnormal noise identification and control of the air conditioner.In this thesis, based on the theory of spectrum analysis and sound intensity analysis, we identify the abnormal noise sources and the spectrum characteristic by using the B&K testing system. All above will work as a foundation of the future noise control. The spectrum analysis part mainly consists of CPB analysis and FFT analysis. The CPB analysis lays stress on the whole change trend, while the FFT analysis lays stress on specific frequency distribution. Besides, the sound intensity analysis is aimed to locate the accurate situation of the abnormal noise sources. Second, according to the sound quality theory, the subjective evaluation metric is established by analyzing the air conditioner's acoustics characteristic. In the end after we make sure that the resonance does not exist in the system, we seek for the methods for controlling the abnormal noise by researching the arising mechanism of abnormal noise. Besides, the design and calculation of the liquid muffler has been focused on and contrast.