2. Sound

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

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. Sound Speed The speed of sound depends on the type of medium through which it travels. –Fastest in solids –Slowest in gases –Speed of sound (at 20°C, dry air) = 342 m/s

10. Sound & Frequency -The frequency of a sound wave depends on how fast the source of the sound is vibrating. -Faster vibrating = higher sound

11. 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

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. Intensity Vs Loudness Intensity –rate at which a wave’s energy flows through a given area. Sound intensity depends on the wave’s amplitude and the distance from the source.

14. Intensity Vs Loudness Measured in decibels (dB). Loudness is how loud or soft a sound is perceived to be (subjective).

15. Ultrasound and Sonar Ultrasound –sound waves with frequencies above the normal human range of hearing. Sounds in the range from 20-100kHz

16. Ultrasound and Sonar Infrasound – sounds with frequencies below the normal human range of hearing. Sounds in the 20- 200 Hz range

17. Ultrasound and Sonar -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

18. Doppler Effect Doppler Effect is the change in sound frequency of a sound caused by the motion of either the listener or the source of the sound. As a source of sound approaches, an observer hears higher frequency. When sound moves away, the observer hears a lower frequency.

19. That’s all folks!