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Points of Articulation
Of course,the lungs,diaphragm,chest muscles,and windpipe also act in the production of speech,but their functions are more or less automatic.
Speech is produced by causing a column of enclosed air to vibrate.It is the same basic process as the production of sound by a wind instrument in music.Air is forced under pressure from the lungs through the windpipe(trachea)to the voice box(larynx),a structure that sits on top of the windpipe and contains the vocal cords,as they are called.(These are not cords at all,really,and would be more properly named bands or membranes.)The vocal cords have the capability of entirely closing off the opening(glottis)and can hold back considerable air pressure(as when a person coughs or strains to lift a heavy weight).They can also assume other positions.They may be widely opened,allowing the air to pass unimpeded,or they may be closed almost but not quite completely so that the escaping air,forced through the narrow opening between them,causes them to vibrate like the reed in a musical instrument.This vibration makes the all-important vocal tone,known technically as voice,without which speech would be impossib.Speech sounds that have this tone as part of their makeup are called voiced,and those without it are called unvoiced or voiceless.Varying the amount of tension on the vocal cords causes the vocal tone to vary in quality and in number of cycles per second;in other words,the timbre and pitch of the tone can be changed voluntarily,within limits,by the speaker.
The air stream issuing from the larynx,with or without voice,can now be modified in many ways during the stage of articulation.Almost all the parts of the throat and lower head that are accessible to the air stream can take part in articulation.For discussion purposes,we can divide these parts into three groups:resonating cavities,articulators,and points of articulation.
Resonating Cavities:The size,the shape,and the material composition of the vessel enclosing a vibrating air column all have an important effect on the quality of the sound that comes from it.There are quite a few spaces in the speech tract that affect sounds by their resonating qualities;in acoustic terms,they reinforce(amplify)certain frequencies and suppress or weaken(dampen)others.In addition to the sinuses and other spaces in the head,which function passively and without the control of the speaker,the resonating cavities involved in speech production are these:the pharynx,the space formed by the root of the tongue and the walls of the throat,which affects the sound by its shape;the nose,which adds a quite distinctive quality to the sound if the air is allowed to pass through it,whether or not the mouth is involved at the same time,and,finally,the mouth,the most important of all because it contains a number of highly mobile organs and can assume a tremendous number of different shapes.
Articulators:These are mobile organs that can be brought close to,or into contact with,various locations in the speech tract(known as"points of articulation")so as to stop or impede the free passage of the air stream.The manner of articulation is determined by the kind of closure or near closure that is made,as well as its manner of release.The"articulators"are the lips,especially the lower one;the tongue,usually divided into four parts:tip,front,middle,and back;the uvula,and,to an extent,the jaw.
