Retraction notice to Air-coupled ultrasonic signal processing method for detection stomata defects in materials [JNDT 92 (2017) 167–176](S0963869516302924)(10.1016/j.ndteint.2017.08.007)

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Authors due to the following errors reported in the paper which were not identified at an earlier stage: 1.The title of the article is not suitable and needs to be modified. 2. The processing effect of Fig.14 needs further improvement, i.e. the top right corner of the figure still contains noise information. 3. Fig.11 and Fig.15 need correction. The authors would like to apologize for the scientific errors on their part.