CHAPTER 2: SOUNDSection 4: How you Hear Sound

Discover Activity: Where is Sound Coming From?1. Ask your partner to sit on a chair, with eyes closed2. Clap your hands near your partner’s left ear. Ask your partner

what direction the sound came from. Record the answer.3. Now clap your hands near your partner’s right ear. Again, ask

your partner what direction the sound came from and record the answer. Continue clapping in different locations around your partner’s head and face. How well did your partner identify the directions the sounds came from?

4. Switch places with your partner and repeat step 1-3.Observing: From which locations are claps easily identified? For which locations are claps impossible to identify? Is there a pattern? If so, suggest an explanation for the pattern.

I. The Human Ear:A. Three sections to the Ear:1. outer ear = funnels sound waves2. middle ear = transmits the waves inward3. inner ear = converts sound waves into

a form that travels to your brain.B. Outer Ear:1. looks and acts like a funnel2. collects sound waves3. ear canal: a narrow region that is a few cm’s long

and ends at the eardrum

4. eardrum- a small tightly stretched, drumlike membrane.

a. Sound waves cause the eardrum to vibrateC. Middle Ear:1. located behind the eardrum2. contains the three smallest bones in the bodya. Hammer-attached to the eardrum (also vibrates)b. Anvil-receives vibration from the hammerc. Stirrup-receives vibration from the anvil

D. Inner Ear:1. Separated from the middle ear by a membrane2. Contains the cochlea- a fluid-filled cavity shaped like a

snail shell. a. Contains more than 10,000 hair cellsb. Hair cells carry the sound waves as messages to

the auditory nerve which carries the signal to the brain.

II. Hearing Loss:A. When a person has a hard time hearing soft sounds or high-pitched soundsB. Causes of Hearing loss:1. injury- eardrum is damaged

or punctured. - try not to put things in your ears2. infection – damages the delicate

inner ear

C. Causes of Hearing Loss cont’d:3. exposure to loud sounds- causes damage to hair

cells in the ear

- damaged cells do not transmit signals to the brain

4. aging- occurs graduallya. Hair cells in the cochlea die and are not replacedb. Results in not being able to hear high soundsc. Wear ear protection to avoid hearing loss

D. Hearing Aids- 1. can restore some lost hearing

2. amplify sounds coming into the ear

3. can amplify specific frequencies as well