SONG Weihua^1,2 WANG Xiaomin¹ LI Mingxuan¹  

(1　　　　 Institute of Acoustics, Chinese Academy of Sciences Beijing 100080) 

(2　　　　 Graduate School of the Chinese Academy of Sciences  Beijing 100029) 

Received Jan. 19, 2007 

Revised Feb. 5, 2007 

Abstract  The electromagnetic ultrasound is used in the detection of interfaces of the adhesive multilayer structures to solve the unstable coupling problem in ultrasonic testing by traditional piezoelectric transducers. Based on the analysis of the transforming mechanism of electromagnetic ultrasound energy and the resultant dead zone from mutual inductance of the transducer, the wavelet filtering by soft-thresholding and adaptive noise canceling methods are used simultaneously to the detected electromagnetic ultrasonic signals to overcome the drawbacks of the low signal to noise ratio (SNR) and the wide intrinsic dead zone of the transducer. Processed results in the interface detection of a three layered adhesive sample of steel and rubber materials demonstrate that the wavelet filtering enhances the SNR about 12dB while the adaptive noise canceling narrows the dead zone effectively.

PACS number: 43.35, 43.60