Listenability Formula for Grading English Listening Comprehension Materials Based on Two Factors of Speech Rate and Length of the Unit of Utterance

本研究是提出英语听力教材可听性公式的初步尝试。研究表明：(1)清晰度和发音单位长度这两个因素对听力理解的影响是根据听力理解测试成绩计算出来的。计算平均发音率、平均发音单位长度和它们的标准差分数，得到公式的常数。(2)不同类型的演讲、阅读、采访和电影对话，语速与语音单位长度之间的关系强度显著不同。在这些类型中，没有被置于某种语法边界上的停顿所包围的语音单位与包含两个以上句子的语音单位的比例是不同的。(3)被停顿包围的话语的长度随着语音变得更快而变长，音调单位的长度随着语音变得更快而变长，并且音调单位的长度随语速的变化小于被停顿包围的话语的长度的变化。(4)从听者的角度重新考虑了话语长度和语速、静音间隔等时间变量。针对听觉记忆能力，提出了一种教学方法(听力理解)和一种设备，即听觉增强器。

This study is an initial attempt to propose listenability formula for English aural textbooks. The study demonstrates the following : (1) The effect of the two factors, articulation rate and length of the unit of utterance, on listening comprehension is calculated upon the results of listening comprehension test scores. The average articulation rate, the average length of the unit of utterance and their standard deviation scores are also calculated to get the constants of the formula. (2) The strength of the relationship between the speech rate and the length of the unit of speech is significantly different depending on type of speech, reading, interview and film dialogue. The ratio of the unit of speech surrounded by pauses which are not placed on a certain kind of grammatical boundary and that of the unit of speech which contains more than two sentences is different among these type. (3) The length of the utterance surrounded by pauses becomes longer as the speech becomes faster, the length of the tone unit becomes longer as the speech becomes faster, and the change of the length of the tone unit with the speed of speech is smaller than that of the length of the utterance surrounded by pauses. (4) Length of the utterance and temporal variables such as speech rate and silent interval are reconsidered from the viewpoint of the listener. Teaching methodologies (listening comprehension) and an apparatus, i.e.an auditory enhancer, are proposed with respect to auditory memory capacity.