The necessity for improving the English listening ability of Korean learners has been emphasized since the ultimate goal of English education converted to CLT(Communicative Language Teaching) in Korea. Verbotonal Approach as an auditory-based strategy has been proved to be effective substantially in maximizing the listening skill of spoken foreign language. The purpose of this study is to find out an efficient way of improving listening ability for Korean middle school students by employing OFH(Optimal Frequency of Hearing) using Tonality Word Sentence Test, before & after using Listen II Verbotonal training unit based on VTS(Verbotonal System). The results of the listening tests showed that the listening ability of the subjects increased by 16.7% on the words and by 5.5% on the sentences after using Listen II, compared with before using Listen II and that the improvement rate of listening ability on the level of words is much higher than that on the level of sentences. From the results, we can come to a conclusion that training the listening skill with words in mid-tonality and low-tonality based on OFH might give a great positive effect in improving listening ability for Korean learners of English.