Retraction:Air-coupled ultrasonic signal processing method for detection Stomata defects in materials

In order to improve signal-to-noise ratio (SNR) of air-coupled ultrasonic signal in the detection Lithium Battery, and achieve detection of Stomata defects in this kind of materials, a new signal processing method is proposed. The new signal processed can effectively filter noise and significantly improve the amplitude of transmission signal. Furthermore, the selection principle of parameters for the new signal processing method is studied. Successful results are presented in Lithium Battery. An improvement in SNR up to 27.95 dB is attained compared with the original received signal. The quantitative accuracy of defects in C-scan image based on the new signal processing method is also very remarkable, and defects as small as Φ3mm can be easily identified.