Sound

1. Sound

2. Overview • The Facts of Sound • The Ear and Sound • Sound Vocabulary • Musical Instruments and Sound

3. 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

4. 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

5. Vibration • Back and forth movement of molecules of matter • For example,

6. 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.

7. 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

8. 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

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

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

11. 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.

12. 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.

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

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

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

16. Ultrasound and Sonar • Sonar -An instrument that uses reflected sound waves to find underwater objects • For example, Humans use sonar to locate or map objects 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

17. 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.

18. That’s all folks!