Q1.
How do humans and animals create sound? While talking or singing, gently touch your throat. Do you feel vibrations anywhere?
Answer
Yes — you feel a distinct buzzing in the front of the throat, at the voice box (larynx).
In humans and many animals, sound is produced by the vibration of the vocal cords — two tightly stretched muscular flaps inside the larynx. Air pushed up from the lungs forces its way between them and sets them vibrating, and those vibrations become the sound of your voice.
- The tongue, lips, mouth and nasal cavity then shape that raw buzz into speech or music.
- Animals do it in other ways too: grasshoppers and crickets rub their wings or legs together, so the rubbing surfaces are the vibrating source.
Why the pitch of a voice differs: the vocal cords behave like the stretched rubber band of Activity 10.1. During adolescence, boys' vocal cords lengthen and thicken, so they vibrate fewer times per second — lower frequency, and the voice 'deepens'. The exact tone of each person also depends on the shape of the throat, mouth and nasal cavities, which is why you can recognise a friend's voice instantly.
Check it yourself: hum with your fingers on the throat, then whisper the same words. The buzzing disappears when you whisper — in a whisper the vocal cords are not made to vibrate.