Abstract: Measuring methods of noise peak to peak voltage (VPP) and noise root mean square (RMS), noise influence factors and sources, and ratio of VPP to RMS are researched in the paper. The results indicate that rolling tubing noise mainly appears periodically and drawn tubing (Inconel690 alloy tube)noise mainly occurs randomly, and the ratio of VPP to RMS is recommended to be π. Additionally, the influence of noise on defects (pitting and crack) is also researched.