Lesson Three: Sound and Hearing Studio Magic Lesson Three: Sound and Hearing

To be able to describe how sound waves travel and how we hear them. Expected Learning: To be able to describe how sound waves travel and how we hear them.

Key Words: Speed Decibel Cochlea Medium Ear drum Cilia

Sound waves need a material or a “medium” to travel in. Sound and Mediums Sound waves need a material or a “medium” to travel in.

Ponder….? Why did this movie have the tag line “In space no one can hear you scream”

Mediums Sound can travel in solids, liquids and gasses. The denser the material, the faster the wave travels. Eg Sound in air – 1000 km/hr Sound in Water – 5,300 km/hr Sound in Bricks – 15,000 km/hr

Sound waves carry energy into your ear. So, here’s how you hear: Sound waves carry energy into your ear. This makes your ear drum vibrate. Explain

Your eardrum passes on the vibrations to the tiny bones of your middle ear – the ossicles. Explain

The vibrating ossicles transfer energy to the cochlea. Here, the vibrations travel through a liquid. Explain

Tiny hairs – cilia – hang down into the liquid Tiny hairs – cilia – hang down into the liquid. Vibrations travelling through the liquid push the hairs. Nerve cells on the hairs detect this movement. They send signals to the brain. You hear the sound. Explain SS3

Sadly, very loud sounds push the hairs too far. They are damaged. For-ever. Explain

Task One: Watch the “ear animation” video in your studio magic folder. In your book, answer the questions on the next slide :

Questions 1. How does the outer ear’s shape help us hear? 2. How do the bones in the ear make sounds seem louder to us? 3. What part of the cochlea actually picks up the sounds? 4. (Extension) – Why do you think the cochlea is curled up?

How loud? The loudness of sounds is measured using a unit called the Decibel. The softest sound most humans can hear has a loudness of 0 decibel. Sounds above 120 decibel cause pain and instant damage. (note : the word decibel has no plural , like the word sheep)

An example In your studio magic folder you will find 3 sound files. Play the reference sound. Leave your volume settings the same , and play the Plus 10 and minus 10 sounds. These sounds are 10 decibel louder and 10 decibel softer than the reference sound.

Task two: Research Find the answers to the following questions and write your answers in your book. 1. The space shuttle taking off was one of the loudest sounds made by humans – what Decibel level was it? 2. What is Tinnitus and what does it have to do with this topic?