Now let's briefly discuss consonants. Much of the clarity of your speech depends upon your pronunciation of the 25 consonants in the English language. Consonants are speech sounds formed by first 1)blocking air off at some point in the vocal 2)tract. And then releasing the air stream at another point in the tract.
Briefly there are at least three ways to classify consonants. But let's look at one of the simplest classifications, whether the consonants are voiced or unvoiced. For example consider the consonant [b] as in the word BABY and [p] as in PAPA, both sounds are formed in exactly the same way. The breath is first blocked by the lips then released as a quick puff of air. The difference is that the vocal chords vibrate or produce 3)phonation when [b] is produced, but they don't when [p] is formed.
If you listen closely as you carefully produce the consonant [b] as in BABY, you'll heara small 4)grunting noise before the [b] sound is formed. That 5)buzzing noise was produced by the vocal chords. So [b] is a voiced consonant. Now once again form the consonant sound [p] as in PAPA. It's a puff of air. No phonation is present.
As Betty said these speech sounds are classified according to several systems. Another 6)classification system involves the ways in which sounds are produced by the 7)articulators. [b] and [p] are also classified as 8)plosive consonants. Think of them as explosives, and you'll get the idea. They can sound like 9)miniature explosions especially if you are speaking into a microphone. And we’ll give you some tips about speaking in the microphones later in this programme. Suffice it to say, spoken, face to face plosive consonants can also produce a mini shower.
So work on producing plosives in a less dramatic manner. That's simply involves releasing the air in a more controlled way.
The consonant sound “s” [s] as in the word SNAKE is called a civilent. Make a 10)hissing sound with me, now [s]. That sound is produced by 11)friction as the air stream passes through the articulators, in this case your teeth. Notice that as you produce an [s] the tongue is slightly 12)cupped, with its tip very close to the front teeth. The teeth are almost touching, and the lips are slightly spread.
Another group of consonants are called 13)semivowels because they include a vowel sound, but are used in speech as consonants. Produce the semivowel “r”[r] as in ROUGH, produce it again slowly, you’ll discover that this sound is actually [aur], a vowel sound starts it. However the speech sound [r] is used as a consonant. The alphabet letter “w”, the speech sound [w] as in WATER is classified as a consonant, but it uses as a vowel sound. Pronounce it slowly [w], WATER, WATER. You see the [w] sound actually starts with a vowel sound [u].
And watch out for 14)nasals. There are only three primary nasals in the English language. [m], [n] and the -ing  ending of any words, SWINGING, RUNNING. They may cause excess nasality if you prolong them.
The inaccurate or incorrect production of the consonant sounds of standard American English are omitting consonants from certain words also can lead to speaking in accented form of American English. For example a speaker may say [fa:m] instead of [farm] or [bidnis] instead of [biznis]. But it's also important to add that the educational level attained by a speaker, his or her social background, ethnic heritage and even age or 15)gender can lead to speaking standard American English with an accent or a dialect. In a study of working class laborers in America, woman were found to use the “-ing” ending on words more frequently than men. Another study found that people whose income fell below a certain level were more likely to omit the [r] from words.
1) block v. 阻碍
2) tract n. 行迹
3) phonation n.（语音）为（某个连续浊辅音或元音）发音
4) grunt v. 咕哝，嘟囔
5) buzz v. 嘤嘤声，嗡嗡声
6)classification n. 分类
7) articulator n. 发音的人或物；（语音）发音器官 8) plosive a. 爆破音的
9) miniature a. 小规模的；小型的 10) hiss v. 发出嘶嘶声
11) friction n. 摩擦
12) cup v. 使成杯形
13) semivowel n. 半元音
14) nasal n.（语音）鼻音
15) gender n. （男性，女性的）性