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How sound waves are produced

1. Your muscles push air form your lungs and through the narrow opening between the vocal chords.

2. The force of the air causes the vocal chords to vibrate.

3. The vibrating vocal chords produce sound waves.

How sound waves are detected

1. Your outer ear collects sound waves and reflects them into a tiny tube called the ear canal. At the end of the ear canal is a thin, skin- like membrane stretched tightly over the opening called the eardrum. When a sound wave strikes the ear drum, they make it vibrate.

2. The middle ear contains three tiny, connected bones called the hammer, anvil, and stirrup. These bones carry vibrations from the ear drum to the inner ear.

3. One of the main parts of the inner ear, the cochlea, contains about 30,000 hair cells. Each of these tiny hair cells has tiny hairs on its surface. The hairs bend as a result of vibrations. This movement triggers changes that cause the cell to send electrical signals along nerves to your brain. Only when your brain receives and processes these signals do you actually hear a sound.

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