The proposed TD method is the first data - specific metric to detect adversarial audio , which focuses on how many adversarial instances are captured ( true positive ) without affecting benign instances ( false positive ) . Therefore , we report the area under curve ( AUC ) score to evaluate the detection efficiency . For the proposed TD method , we compare the temporal dependency based on WER , CER , as well as the longest common prefix ( LCP ) . LCP is a commonly used metric to evaluate the similarity between two strings . Given strings s 1 and s 2 , the corresponding LCP is defined as max s1[:k]=s2[:k ] k , where [: k ] represents the first k portion of a sentence .