复习资料（2.2）
2、What is phonetics?
什么是语音学？
Phonetics is defined as the study of the phonic medium of language；It is concerned with all the sounds that occur in the world’s languages.
语音学研究的对象是语言的声音媒介，即人类语言中使用的全部语音。
There are three branches of phonetics. They are:
Articulatory phonetics （发音语音学）, it studies the speech sounds from the speaker’s point of view. It studies how a speaker uses his speech organs to articulate the sounds.
Auditory phonetics （听觉语音学），it studies the speech sounds from the hearer’s point of view. It studies how the sounds are perceived by he hearer.
Acoustic phonetics（声学语音学），it studies the speech sounds by looking at the sound waves. It studies the physical means by which speech sounds are transmitted through the air from one person to another.