Speech is an ability to express our feelings, thoughts and has evolved with humans in the last few thousand years. Although all animals possess vocal cords and produce typical noises and sound, speeches and musicals are only connected with humans. Evolution of speech and in turn that of larynx, the voice box of our body resulted in the developmental activities like speaking, and singing. But larynx singularly does not control all the functioning of the sound. Rather it works together with rib cage, back muscles, lungs, oral cavity and vocal cords to create the magic of sound of speech.
Vocal cords are also called as plica vocalis in Latin. These are the two folds related to mucous membrane that move further into the larynx’s interior cavity and are basically the producer of voice. Sound is generally created when the folds vibrates as a response to the air movement inside these folds when lungs exhale the air. The pitch of voice too is determined by the vibration frequencies. As compared to men in women and children, the vocal cords are shorter as well as thinner due to which their voices are much higher pitched.
Both the vocal tract as well as the vocal cord has a major role to play in the production of speech. Several organs are present inside the vocal tract that regularly monitor and control the centers of speech. For this they take the help of brain’s internal feedback. Speech sounds are created when lungs exhale air due to which there is vibration in the vocal cord and turbulence is created inside the vocal tract at some juncture. The sound harmonics are significantly influenced by vocal tract shape. The vibration of vocal cord and varying shape of vocal tract creates the typical individual speech sounds.
The place of vocal cord is inside the Adams apple of larynx. Vocal cord is known to create two types of speeches:
The vibrations occurring inside the vocal cord decides whether the speech is going to be voiced or unvoiced. Also the constrictions formed inside the vocal tract due to the turbulence air flow are responsible for these two types of speeches. Vibration frequency of vocal cord is determined by certain factors like muscle tension, mass and length of muscles. The reason why people have different types of voices is because these determinants vary according to age and sexes. The vocal cord vibration creates harmonics and it decreases in the wake of increasing frequency.
The vocal cords that are also medically termed as vocal folds are mucous membranes that open and also close in a snap during the process of speaking, singing or while we make noise. When the air pressure is increased against the folds of vocal cord they snap and produce a sound. When the snapping is gentle, the action produces very soft and gentle sound and when the snapping is forceful, we hear loud sound or noise. The pitch goes on increasing with the increase in the frequency of opening and closing of the folds. In a normal speech vocal cord has been known to perform the action of opening and closing 100 times/ second.
The “false” vocal folds or cords are placed above the real vocal cords and prevent the substances like food from entering inside trachea while we are swallowing it. They are not in any way related to the function of singing or speech.
Surprisingly, the vocal quality is not influenced by the vocal cord or vocal tract. Rather other anatomical structures like palate, tongue, nasal cavity, oral cavity, chest cavity, pharynx, sinus cavity etc influence it. Vocal cords on their own create only a buzzing like sound, but resonators contribute in making the sounds essential for music and speech.