Speech organs for pronunciation ;The larynx -Voicing

Speech organs for pronunciation ;The larynx -Voicing

The statement above that the airstream “emerges from the trachea (windpipe) into the throat” is actually an oversimplification Before the air reaches the “throat”, it has to pass through one of the most important speech organs, the LARYNX. It’s at this point that the first possibilities occur of modifying the airstream and generating sound.
The larynx can conveniently be thought of as an irregularly-shaped, hollow box made of cartilage, which sits on top of the trachea. (This is reflected in the non-technical name for it: the “voice-box”.) The front of the larynx can easily be seen and touched: it forms the projection an inch or two below the chin, known as the “Adam’s apple” (more prominent in males than in females - hence presumably the name).
Across the interior of the larynx are stretched two horizontal sheets of muscle tissue. When these are relaxed and wide apart, then the air is free to pass between them. This is how they are held for normal respiration. But if they are brought together with their inner edges in close contact, then air is prevented from entering or leaving the lungs: the only way in or out is through the larynx cavity, which is now sealed off . This is the configuration for swallowing:it prevents not only air but, more importantly, foreign bodies from getting into the lungs.
A third possibility The sheets of muscle are again in contact, but very loosely this time, instead of
being pressed firmly together . As a result, air is able to pass through, but not freely: it has to force
its way, so to speak. This sets the inner edges of the muscles into vibration, and this vibration causes a disturbance in the airstream - i.e. a sound wave. The sound is greatly amplified by the resonance of the mouth and throat cavities, and the result is: the human voice. As a consequence, the inner edges of the muscles stretched across the larynx are known as the vocal folds (alternatively vocal cords or, occasionally, vocal lips). Say aaah, for instance: the sound you’re producing is amplified vocal fold vibration. In essence, the vibration is similar to the effect which you get by folding over a piece of thin paper and blowing between the edges.
The space between the vocal folds is known as the GLOTTIS.

The vocal folds also control the pitch of the voice. As with the strings of a musical instrument, the greater the tension, the higher the pitch. The larynx is provided with a number of muscles which, together with the vocal fold muscles
The larynx and vocal folds of women and children are smaller than those of adult males: hence the difference between soprano and bass voices. When a boy’s voice “breaks” at puberty, this is due to a rapid increase in the size of the larynx. Subtle and complex adjustments of the glottis give rise not just to “normal” voice at a range of pitches, but also to such varied vocal effects as stage whisper, falsetto or so-called “breathy voice”. But it’s worth remembering that voice is a only secondary adaptation of the “vocal” folds, despite the name. (After all, other mammals and even reptiles have a larynx too.) Biologically the primary function of the larynx in general and the vocal folds in particular, is to serve as a valve for the lungs. As has been mentioned already, it’s advisable to close the glottis firmly when swallowing - we all do so instinctively in fact. A second important reason for having a larynx is that the closed vocal folds, by holding back the airstream, can
create a firm column of air in the chest, against which we can push during various kind of physical exertion. Weightlifting, defecation and childbirth all involve a tightly closed glottis!

Voicing

Although it’s merely a biological by-product, the importance of voice for languages can’t be overestimated. All vowel sounds are normally uttered with the vocal folds in vibration (i.e. they are voiced) and so are around half the consonants.
Take [s] and [z], for instance. As we’ll see in more detail later, for both these sounds there is a constriction of the airflow just behind the upper front teeth. The difference between them is that [s] is voiceless (vocal folds held apart in the  position and the airstream able to pass between them unhindered) whereas [z] is voiced, with the vocal folds in  position and consequently in vibration. You should be able to spot the absence or presence of voicing easily enough if you say [s] ... [z] ... [s] ... [z] loudly several times in alternation. The difference becomes even more obvious if you place your fingers firmly over your ears while doing so.
The same relationship exists between the th in thin and the th in this. This time, unfortunately, the spelling doesn’t show any difference. But by repeating these two words in alternation you should be able to tell that in the case of thin we have a voiceless th and in the case of this a voiced one. The phonetic alphabet uses a separate symbol for each: [t] (read “theta”) for the th of thin and [ð] (read “thorn”) for the th of this. (Apologies for the fact that the name “thorn” actually begins with voiceless [t]. Perhaps ill-advisedly, the [ð] symbol is called after a letter of the Old English alphabet.)

Yet another voiceless/voiced pair is [p] and [b]. Try saying [apa] and [aba] in alternation. In both cases there’s a momentary blockage of the airstream between the lips when the consonant is made. What makes the difference between them is voicing (present for [b], absent for [p]).
In fact almost all consonants come in voiced and voiceless pairs - an ingenious use of a single feature (voicing) in order