10.2. Sound Produced by Humans

Speak loudly for a while or sing a song, or buzz like a bee. Put your hand on your throat as shown in Fig. 10.8. Do you feel any vibrations? In humans, the sound is produced by the voice box or the larynx. Put your fingers on the throat and find a hard bump that seems to move when you swallow. This part of the body is known as the voice box. It is at the upper end of the windpipe.

When humans produce sound by speaking or singing, this involves a part of the body known as the larynx, or voice box. The process begins when we push air from our lungs through this voice box. By placing a hand on the throat while speaking, you can feel vibrations produced in the larynx. This is because the vocal cords, which are two flexible bands of tissue, vibrate as air passes through them, creating sound. These vibrations are essential for making different pitches and tones.

Imagine blowing air through a balloon. When the air passes through the opening, the balloon vibrates and makes a sound. Similarly, our voice box vibrates when air passes through it, enabling us to produce sounds.

Two vocal cords are stretched across the voice box or larynx in such a way that it leaves a narrow slit between them for the passage of air. When the lungs force air through the slit, the vocal cords vibrate, producing sound. Muscles attached to the vocal cords can make the cords tight or loose. When the vocal cords are tight and thin, the type or quality of voice is different.

The vocal cords function by opening and closing to allow air to pass through and create sound. When air is forced from the lungs through the narrow opening created by the vocal cords, they vibrate at different frequencies depending on how tight or loose they are. If the cords are tightened, they produce a higher pitch sound; if they are relaxed, the sound is lower. This is how voices vary in pitch and tone.

Consider a guitar string: if you pluck it gently, it vibrates slowly and produces a lower sound. If you pluck it tightly or with more force, it vibrates faster and produces a higher sound. Our vocal cords work in a similar way to create different sound pitches.

Activity 10.6 Take two rubber strips of the same size. Place these two pieces one above the other and stretch them tight. Now blow air through the gap between them. As the air blows through the stretched rubber strips, a sound is produced.

In this activity, when you blow air through the space between two tight rubber strips, the strips vibrate and produce sound. This demonstrates how our vocal cords operate. The sound is generated by the vibration of the rubber, just as sound comes from the vibrations of the vocal cords when we speak or sing.

A similar principle is used in wind instruments, like a flute. When a musician blows air through the opening, the air vibrates the reeds or edges of the flute, creating music. This shows how blowing air can make different objects vibrate to produce sound.

The vocal cords in men are about 20 mm long. In women, these are about 15 mm long. Children have very short vocal cords. This is the reason why the voices of men, women, and children are different.

The length of the vocal cords plays a significant role in determining the pitch of a person's voice. Generally, longer vocal cords produce lower pitches, which is why men, having longer cords, tend to have deeper voices. Women and children, with shorter vocal cords, typically have higher-pitched voices.

Think of tuning forks: larger ones produce lower tones while smaller ones produce higher tones. Similarly, the size of our vocal cords affects the sound our voice produces.

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