2. Sound Waves Over the next few weeks, we will discuss… How We Hear Properties of Sound Using Sound

3. Sound Waves How We Hear

4. Answer the following questions as you watch: Answer the following questions as you watch: 1. What three bones are found inside your ear? 2. What does my body do that allows me to hear? 3. What happens to your hearing if the hairs in your ears die or become paralyzed? 4. What other factors might cause hearing loss?

5. 1) What are the three bones found inside your ear? Hammer Anvil Stirrup hammeranvilstirrup

6. 2) What does my body do that allows me to hear? 1.A sound wave is FUNNELED through the outer ear into the middle ear canal 3.These vibrations are transmitted to the three small bones : the hammer, the anvil and the stirrup 2.The eardrum vibrates and AMPLIFIES the sound when the wave hits it (The eardrum is a membrane that stretches across the ear like a drumhead)

7. 4.These bones AMPLIFY the sound and send the energy to the inner ear 5.Hair tipped cells inside the cochlea vibrate, GENERATE SIGNALS containing information of the sound and send them to the brain 6.The brain INTERPRETS these signals as sound to tell you about the pitch, volume and length of the sound you have heard

8. 3) What happens to your hearing if the hairs in your ears die or become paralyzed? ▪ You go deaf! Wait… what did you say?

9. 4)What else might cause hearing loss?  Old age 28% –Higher frequencies are easily lost –Sounds appear distorted –Sounds such as “s,” “f,” “sh,” “ch” are hard to hear –30% of people over 65 have some hearing loss to aging  Exposure to loud sounds 33.7% (leading cause of hearing loss) –Constant exposure to loud noise can damage hair cells in cochlea  Other 16.8 –Mammals cannot make new hair cells  Infection / Damage / Injury to ear 17% Disease/sickness  Born with hearing loss 4.4%

10.  The AMPLITUDE! – The amount of energy, The louder the sound, and the longer you listen to it, the more hearing you will lose!  The intensity of a sound is how much energy passes through a given area/distance in an amount of time  Loudness is the perception of how much energy a sound wave carries

11. o 0 dB = Threshold (softest sound we can hear) o 15 dB = Whisper o 20 dB = Cat purring o 60 dB = Normal talking o 85 dB = Noisy lunchroom (prolonged exposure can cause damage) o 110 dB = Lawn mower/Hair dryer o 115 dB = iPod at peak volume o 120 dB = Pain threshold o 150 dB = Jet plane taking off  At the human threshold, the eardrum moves 1 billionth of a cm! –The amount of energy carried by sound waves is described by a scale called The Decibel Scale

12. Hearing Loss Facts Hearing damage begins to occur at 85 dB –Some rock concerts produce sound levels as high as 120 dB! –iPod volumes peak at 115 dB Amount of damage depends on intensity of the sound and the length of time that a person is exposed to it

13. Sound Waves Properties of Sound

14. Sound Waves Sound waves are mechanical waves that require a medium to travel and carry its energy. –Sound can’t travel in a vacuum like in outer space because there are no particles to carry the energy. The type of mechanical wave sound is, is a longitudinal wave. –“Sound waves are longitudinal” –Many machines that measure sound use a transverse wave picture to show the sound wave properties of amplitude and wavelength because it is easier. Compression = crest Rarefaction = trough

15. The number of complete waves that pass a given point in a certain amount of time Frequency is measured in units called “Hertz” –1 Hertz is equal to 1 wave per second –100 Hz is equal to 100 waves per second High FrequencyLow Frequency Frequency

16. Pitch is how high or low a sound is, and it corresponds with the sound’s frequency –High pitch sound waves have shorter wavelengths –Lower pitch sound waves have longer wavelengths High pitchLow pitch

17. –Detectable Sounds –Human ear detect sound waves 20 Hz - 20,000 Hz –Dogs hear frequencies up to almost 50,000 Hz –Dolphins and bats hear as high as 150,000 Hz

18. Mythbusters Video “Breaking Glass” In this video, Adam and Jaime try to test the myth that a singer can break glass using only their voice.

19. Sound Waves Using Sound

20. The Doppler Effect: The change in frequency that occurs when a source of sound is moving relative to a listener Pitch is affected as an object moves towards you, then away from you Sound spreads out as it travels –Object moves towards you making sound waves compress: results in higher pitch –As the object moves away from you, sound waves spread apart: resulting in lower pitch Ex: Radar guns – measure speeds of cars/baseball pitches The radar gun uses the change in frequency of the reflected wave to determine the object’s speed

21. –Sound waves are emitted by an animal, hit an object and reflect back towards the source, which allows the animal to navigate, hunt, and communicate Bats:Bats: Emit high pitched squeaks to determine placement in time/space, locate food or other objects Dolphins:Dolphins: Use high-pitched clicks to navigate Humans:Humans: Use ears to interpret echoes (to estimate size/shape of room)

22. –High-frequency sound waves above 20,000 Hz –reflect off body structures, and the resulting “echo” is then sent to a computer, that receives these reflected waves and makes images of the structure Examine developing fetus Examine internal organs –Alternative to surgery – focusing sound waves on kidney stones or gallbladder stones can break them up so that they may be safely passed through the body

23. Extremely low frequency waves below 20Hz emitted by elephants that allows them to communicate over long distances

24. –The amount of time it takes an echo to return depends on how far away the reflecting surface is –Use sound waves to map objects underneath a body of water Used to map undersea features, detect submarines, schools of fish and other objects