Hearing begins when the outer ear collects sound waves from the air and guides them into the ear canal. These waves carry energy from vibrating objects, such as voices, musical instruments, or speakers. The ear changes this wave energy into tiny movements and then into electrical signals the brain can understand.
Hearing matters because it helps us communicate, learn, stay aware of danger, and enjoy the world around us.
Inside the ear, the eardrum vibrates and moves three small bones in the middle ear called the ossicles. These bones pass the vibration to the cochlea, a fluid-filled structure in the inner ear lined with sensitive hair cells. Hair cells turn vibrations into nerve signals that travel through the auditory nerve to the brain.
The inner ear also contains balance organs that sense head motion and help the body stay upright.
Key Facts
- Sound travels as pressure waves through air, liquids, or solids.
- Frequency is measured in hertz, Hz, and is related to pitch.
- Human hearing is usually about 20 Hz to 20,000 Hz for young healthy ears.
- The outer ear funnels sound into the ear canal toward the eardrum.
- The ossicles are the malleus, incus, and stapes, and they amplify vibrations.
- Sound path: outer ear -> eardrum -> ossicles -> cochlea -> auditory nerve -> brain.
Vocabulary
- Outer ear
- The visible part of the ear and the ear canal that collect sound waves and direct them inward.
- Eardrum
- A thin membrane that vibrates when sound waves reach it.
- Ossicles
- Three tiny bones in the middle ear that transfer and strengthen vibrations from the eardrum.
- Cochlea
- A spiral-shaped inner ear structure that changes vibrations into nerve signals.
- Auditory nerve
- The nerve that carries hearing signals from the cochlea to the brain.
Common Mistakes to Avoid
- Thinking sound is a substance that enters the ear. Sound is energy carried by vibrations, not matter that fills the ear.
- Forgetting the middle ear bones. The ossicles are important because they amplify and transfer vibrations to the inner ear.
- Saying the brain hears sound directly from the air. The brain interprets electrical signals sent by the auditory nerve after the ear changes sound waves into nerve impulses.
- Using loud headphones for long periods. High sound intensity can damage inner ear hair cells, and these cells usually do not grow back.
Practice Questions
- 1 A sound has a frequency of 440 Hz. How many vibrations occur in 3 seconds?
- 2 A student listens to music for 2 hours each day. How many hours of listening is that in one week?
- 3 Explain why damage to hair cells in the cochlea can cause hearing loss even if the outer ear and eardrum still work normally.