We, the human beings are the luckiest beings as we are gifted with speech. Some animals like the parrot and myna speaks by imitating the voice of their master when they are kept as pets. But no other animals are able to speak. They only produce different sounds according to different situations. So, we, the human beings are able to speak only. Do you know how do we speak? Really, it is very interesting.
Human throat consists of a hollow organ named the ‘sound box’ or ‘larynx’. It is in reality, an enlarged part of the wind pipe. The walls of larynx are made of cartilages and are covered with mucous membrane inside. The cartilage is made up of a very soft bony substance. There are two vocal cords on the two sides of this box. Their movement is regulated by sixteen muscles. When air from the lungs passes through the vocal cords, they begin to vibrate. As a result of these vibrations, sound is generated and we speak.
The sharpness, hoarseness and sweetness of sound depend upon the disturbance of vocal cords. This is regulated by the muscles. When the vocal cords are under higher tension, they can vibrate upto 1000 times per second generating melodious sounds. In fact, more the number of their vibrations, sharper is the sound. On the other hand less the number of vibrations, the heavier is the sound.
The rate of vibrations differs from one person to another. Therefore the pitch of sound also differs in different persons. People with melodious voices have a better developed box as compared to others.
When a child becomes 13 or 14 years old, his vocal cords grow thicker and their frequency of vibrations is checked. This lowers the pitch of the voice. Our chest, stomach, tongue, lips, teeth are also involved in the generation of sound.