2. Sound

3. Overview The Facts of Sound The Ear and Sound Sound Vocabulary Musical Instruments and Sound Doppler Effect

4. The Facts Sound … 1. Is a form of energy produced & transmitted by vibrating matter 2. Travels in waves 3. Travels more quickly through solids than liquids or gases

5. The Ear Sound is carried to our ears through vibrating air molecules. Our ears take in sound waves & turn them into signals that go to our brains. Sound waves move through 3 parts of the ear; outer ear, middle ear, & inner ear. Middle Ear

6. Vibration -Back and forth movement of molecules of matter -For example,

7. Compression -Where molecules are being pressed together as the sound waves move through matter -For example, -a wave travels through the springs just like sound waves travel through the air -the places where the springs are close together are like compressions in the air.

8. Sound Waves -Alternating areas of high & low pressure in the air -ALL sound is carried through matter as sound waves -Sound waves move out in ALL directions from a vibrating object

9. Wavelength & Frequency -Wavelength is the distance between one part of a wave and the same part of the next wave -Frequency is the number of waves moving past a point in one second

10. Pitch A measure of how high or low a sound is Pitch depends on the frequency of a sound wave For example, - Low pitch - Low frequency - Longer wavelength - High pitch - High frequency - Shorter wavelength

11. Sonar -An instrument that uses reflected sound waves to find underwater objects -For example, Animals use sonar or echo location to find their prey; these sounds have such a high pitch or frequency that the human ear cannot hear Humans use sonar to locate or map objects

12. Sound and Instruments -Instruments can be played at different pitches by changing lengths of different parts. -For example, -Another way to make different pitches is to change the thickness of the material that vibrates. -For example, A trombone’s mute absorbs some of the sound waves produced, thus producing a softer note when played.

13. The Doppler Effect

14. The apparent frequency of a sound changes due to the relative movement of the source and/or observer http://www.falstad.com/ripplehttp://www.falstad.com/ripple YouTube - Fire Engine siren demonstrates the Doppler Effect

15. Resting sound source source at rest observer at rest Frequency f s Frequency f o V=340m/s

16. Sound source moving toward observer sourceobserver at rest Frequency f s Frequency f o Observer hears increased pitch (shorter wave length)

17. Sound source moving away from observer source observer at rest Frequency f s Frequency f o Observer hears decreased pitch (longer wave length)

18. Other effects Don’t forget that the loudness of the sound will also change as a sound source passes an observer

19. Other effects The sonic boom YouTube - Sonic Boom - Extreme Close Fly ByRelated Videos

20. Sonic boom When an airplane travels at a speed faster than sound, density waves of sound emitted by the plane cannot precede the plane, and so accumulate in a cone behind the plane. When this shock wave passes, a listener hears all at once the sound emitted over a longer period: a sonic boom. As a plane accelerates to just break the sound barrier, however, an unusual cloud might form. The origin of this cloud is still debated. A leading theory is that a drop in air pressure at the plane described by the Prandtl-Glauert Singularity occurs so that moist air condenses there to form water droplets.

21. Doppler effect in light Δf = (v/c)f when v << c

22. Uses of the Doppler effect Measuring the speed of moving objects (like cars or baseballs Measuring the speed of flow of blood cells in an artery

23. Anechoic chamber: The room that 'sucks out' sound http://www.bbc.co.uk/news/science- environment-21708581 http://www.bbc.co.uk/news/science- environment-21708581

24. Look V-sauce; This is not yellow http://www.youtube.com/watch ?v=R3unPcJDbCc http://www.youtube.com/watch ?v=R3unPcJDbCc http://www.youtube.com/watch ?v=R3unPcJDbCc