1． 结合毕业设计（论文）课题情况，根据所查阅的文献资料，每人撰写2000字左右的文献综述：

1. Introduction

The purpose of the study is to explore the effects of different speaking rates and difficulty levels on EFL learners#8217; listening comprehension. 75% of language communication depends on listening and speaking, among which listening accounts for 45%. Additionally, listening comprehension accounts for 20% in CET4 and CET6 (Huang, 2001). Thus, how to improve and strengthen the students#8217; listening comprehension has become an important subject.

So far, many researches have investigated the effect of different elements on listening comprehension, such as the mastery of the grammar and vocabulary, the accuracy of pronunciation and intonation, etc. (Xu, 2006; Bu, 2009). There are also some researches both at home and abroad (Liu, 1999; Ahmad, Omid amp; Salman, 2012; Roy, 2002; Tauroza,1997) explore the effect of different English accents on listening comprehension.

1.1 Need for the study

Nowadays, many listening materials both have fast and slow speeds, such as BBC, VOA, which shows that people have realized the relationship between speaking rate and listening comprehension. One of the major problems most EFL listeners complain about is that speech that seems to have exerted an influential effect on their listening comprehension (Abdolmajid, 2010). Wang (2007) finds that the difficulty levels of listening text have an effect on listening comprehension. As the main variables and factors in listening comprehension, speaking rates and difficulty levels have succeeded to grab the scholars#8217; attention. Some studies have been carried out to investigate the effects of different speaking rates and different difficulty levels on listening comprehension (Tian, 2002; Rong, 2010).

Listening is one of the core courses of College English and plays an important role in the process of English learning. Although teachers and students have put a lot of time and effort into listening, they still achieve a little. Thus, how to strengthen college English listening is an important subject. The current studies have revealed that speaking rates and difficulty levels do influence on learners#8217; listening comprehension. This research will be carried out to explore the effects of different speaking rates on listening comprehension at different difficulty levels.

1.2 Research purpose

The purpose of the study is to explore the effects of different speaking rates and difficulty levels on listening comprehension. Specifically, with the importance of listening comprehension in English learning, it is significant to explore how the experimental subjects perform when listening materials with different speaking rates and different degrees of difficulty are exposed. Moreover, it is necessary to provide some pedagogical implications on EFL teaching and improve students#8217; listening comprehension with more scientific methods.

2. Literature review

Nowadays, improving students#8217; ability of language communication has been the primary goal in the college English teaching. As listening comprehension plays an important role in English study, it has drawn a lot of scholars#8217; attentions from both home and abroad. However, the present study has viewed speech rate from other perspective to provide some novelty. In this study we will analyze the effects of American accent at different speaking rates on listening comprehension. In this chapter, literature review will be introduced from three parts: the first part will focus on the related empirical studies at home; the second one will emphasize on the related empirical studies abroad; and the third will present the problems in the previous studies.

2.1 Related empirical studies about the effect of different speaking rates on listening comprehension

Liu (2012) explores the influence of different input speech rates on listening acquisition. 80 students from Qufu Normal University are assigned into 4 groups randomly. The listening materials are divided into normal speed (250 syllables per minute) and lower speed (70 syllables per minute). This experiment includes three stages: preheating process (5 minutes), resting stage (10 minutes) and the real testing stage (10minutes). This experiment aims at finding the effect of listening implicit learning on different speaking rates. In the end, he concludes that students#8217; listening comprehension improve more at normal speed than that at slow speed, and that shortening the process from slow to fast input rate contribute to EFL learners.

Du (2013) carries out an empirical study to explore the effect of textual clues on students#8217; listening comprehension and whether this is affected by speaking speed. 36 students who take a senior English course are divided into four groups to listen to the following texts: 1) Speech with clue words at normal speed ; 2) Speech with non-clue words at normal speed; 3) Speech with clue words at slow speed ; 4) Speech with non-clue words at slow speed. The results show that clue words play an important role in English listening and speed does not have a significant effect on listening.

Huei-chun#8217;s (2001) study is conducted to investigate the effects of syntactic modification and speech rate on EFL listening comprehension. The subjects were 168 college freshmen in Taiwan. Given the four versions of the listening passage on syntactic modification (unmodified/paraphrase/simple sentence/mixed), plus two different speech rates (average/slow) for each syntactic version, there were altogether eight versions of the listening passage. Subjects were assigned to one of the eight experimental groups according to the results of a randomized complete block design. After listening to the passage, subjects completed a cloze test. The results confirm the significant role played by speech modification in L2 listening comprehension. The study offers empirical evidences for the facilitating effects of syntactic modification and slower speech rate. Finally, the current study proposes some implications for the instruction of EFL listening comprehension.

Mcbride#8217;s (2011) study investigates the effects of training learners of English as a foreign language with different rates of speech and controls over speech rate. Subjects were put into one of four treatment groups: (A) trained on listening comprehension materials recorded at a fast speed, (B) trained on slow recordings, (C) given some choice about the speed, and (D) allowed sometimes to pause playback. The group that was trained on slow materials fared the best, apparently because their bottom-up processing improved. Other groups seem to have developed their strategic listening skills more, but these did not always transfer as well to other contexts. It was also found that learners performed better when they paced their training over several days.

Griffiths (1990) studies the effect of speech rate on comprehension of a semi-scientific text that was read aloud at three different speech rate levels and found that moderately fast speech rates reduced comprehension, but a slow rate of delivery did not increase comprehension significantly as compared to speech delivered at a normal rate. In another descriptive study, Griffiths (1990) states that language learners are likely to meet a far greater speed of rates than the rates investigated in the earlier study. In a similar study but with different materials (stories rather than semi-scientific texts), Griffiths (1992) conducts an experiment on 24 Omani elementary school teachers for a five-week course. He provided three story passages with three different speech rates: slow speech rates, average speech rates, and fast speech rates. Based on the participants#8217; scores in listening comprehension, he concluded that a slower rate of delivery resulted in better comprehension scores than fast and average rates (although average rates did not lead to better results than fast rates).

2.2 Related empirical studies about the effect of difficulty levels on listening comprehension

In Zheng#8217;s (2010) study, China Daily (CHA) and VOA were selected as the representatives for English news from home and abroad respectively. Two news corpora-CHD corpus and VOA was made from four aspects: phonological, lexical, syntactic and propositional features. The standardized type, average word length, average sentence length etc. were obtained by using Wordsmith Tools 4.0. The proportions of high frequency word in each corpus were obtained by using Vocab Profile computer program. By conclusion, the average speaking rate and information density of each corpus were obtained. It is found that in terms of word length and lexical variation, there is no significant between the two; in terms of speech rate, word frequency and and sytactic complexity, CHD is more difficult than VOA; in terms of propositional, VOA is more difficult than CHD. In order to explore weather there is any difficulty difference in listening comprehension between CHD and VOA news reports, listening comprehension test was administrated by using the listening materials from CHD corpus and VOA corpus (3 from CHD and 3 from VOA). It is found that CHD listening comprehension is significantly easier than VOA. To explain this finding from the perspective of text features, efforts were made to control the effect of item difficulty upon the test result.

Wang (2007) analyzes the listening obstacles (of 100 students in senior #1030;, No.2 Middle school of Wuhan.) caused by listening materials. She clarifies a variety of listening obstacles caused by listening materials, laying the foundation of probing the reasons for them and suggesting strategies in response.

2.3 Problems in the previous studies

In the past several decades, the factors that affect listening comprehension have successfully attracted a lot of attentions and more and more scholars come into notice the necessities of studying the subject on how to improve EFL learners#8217; listening comprehension. Among all the factors that affect comprehension, speech rate and difficulty levels are of crucial importance. However, there still exit some problems in the previous studies.

Firstly, from the previous studies, we can easily find that the studies listening comprehension are relatively few, compared with those on reading comprehension. Furthermore, there were fewer researches about the relationship between the different speaking rates and the difficulty levels of the text.

Secondly, more studies focus on the theoretical analysis of listening comprehension and didn#8217;t put them into practice. In other words, both qualitative and quantitative analyses should be taken into consideration. And attention should be attached to the possible factors which were easily to be ignored.

Thirdly, the experimental samples in most researches are not representative, which lead to the results of their studies inaccurate and unreliable.

To sum up, there are still many problems in the previous studies, which call for the implement of the current study.

References

Abdolmajid, H. (2010). The effect of speech rate on listening comprehension of EFL learners. Creative Education, 2, 107-114.

Ahmad, M., Omid, R., amp; Salman, D. (2012). The effect of non-native accent on Iranian EFL learners#8217; listening comprehension: Focusing on Persian accent of English. Journal of Language Teaching and Research, 3, 967-972.

Bu. Q. L. [卜巧玲]，2009，影响英语听力理解的因素及对策. 宿州学院学报(24)：159-162。

DU, F. Y. [杜方圆], 2013, 语篇线索词和语速对中国大学生学术英语听力的影响. 外语与翻译 (2): 31-38。

Griffiths, R. (1990). Speech rate and NNS comprehension: A preliminary study in time-benefit analysis. Language Learning,40, 311-336.

Griffiths, R. (1992). Speech rate and listening comprehension: Further evidence of the relationship. Tesol Quarterly, 26(2), 385-395.

Huang, T. [黄田], 2001, 美音传播的文化渊源即对我国教学英语的影响. 株洲工学院学报(15): 79-81。

Liu, J. R., et al.[柳加仁]等人，2012，输入语速对外语听力习得影响的实验研究. 外语教学与研究(44)：402-410。

Liu, W. D. [刘卫东], 1999, 浅论美国英语与英国英语发音差异. 江苏广播电视大学学报(10): 96-97。

Mcbride, K. (2011). The effect of rate of speech and distributed practice on the development of listening comprehension. Computer Assisted Language Learning, 24, 131-154.

Ou, Y. C. [欧阳春], 2005, 英国英语和美国英语发音差异的分析. 广西医科大学大学学报(23): 381-382。

Paul, R. (1978). Teaching language as communication. Ox ford University Press.

Rong, T. Y. [容铁愚], 2010, 听者因素, 文本因素, 听力理解. 扬州大学 (06):59-60。

Roy, C., Susan, F. F., Ferenc, B. amp; Chandrika, B. (2002). The Effects of Nonnative Accents on Listening Comprehension: Implications for ESL Assessment. Tesol Quarterly, 36,(2), 173#8211;190.

Tauroza, S., amp; J, Luk. 1997, Accent and Second Language Listening Comprehension. Relc Journal, 28,(1), 54-71.

Teng, H. C. (2001). Impact of speech modification on EFL listening. Conference Proceedings ,3, 532-537.

Tian, L. [田靓], 2002, 言语速度对留学生听力理解的影响. 汉语学习(2): 71-72。

Wang, J. X. [王菊香], 2007,听力材料对中学生英语听力理解的影响及相关对策. 华中师范大学(5): 110-113。

Xu, H. Y. [许红岩], 2006, 论英语教学中影响听力的因素及解决途径. 宿州教育学院学报(4): 126-127。

Zheng, H. M. [郑慧敏], 2010, 基于中国日报和美国之音新闻英语听力材料的听力理解对比研究. 上海交通大学(4): 64-66。