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# Properties Of Sound

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### Properties Of Sound

1. 1. Properties of Sound<br />Page 42<br />
2. 2. Loudness<br />Loudness is your perception of the energy that sound waves have<br />Two key factors<br /> 1. Amount of Energy<br />Amplitude<br /> 2. Distance from the source of sound<br /> Intensity = Energy per second<br />43<br />
3. 3. Intensity<br />43<br />
4. 4. Measuring Loudness<br />Decibel (dB)<br />44<br />
5. 5. Human Pitch<br />Vocal cords in larynx can vibrate 1,000 times/sec<br />45<br />
6. 6. Pitch<br />Depends on the frequency of the wave<br /> High frequency = High pitch<br /> Measured in unit called hertz (Hz)<br /> 80 Hz means 80 waves each second<br />44<br />
7. 7. Pitch<br />Human Hearing<br /> 20 Hz to 20,000 Hz<br /> Above 20,000 Hz can not hear – Ultrasound<br /> Below 20 Hz – Infrasound<br />45<br />
8. 8. The Doppler Effect<br />The frequency of sound changes depending on where you are IF things are MOVING<br />Described by Christian Doppler (1803-1853)<br />The motion of the source adds to the motion of the waves<br />46<br />
9. 9. Sound Barrier<br />Shock wave is formed by the piling up of sound waves<br />People on the ground experience as sonic boom<br />46<br />
10. 10. Music<br />What is the difference between music and noise?<br /> How the sound waves combine!<br /> Music is a pleasing combination of waves<br /> Noise is unpleasant combination of waves<br />48<br />
11. 11. Tones<br />Fundamental Tone = Lowest natural frequency<br />Overtone = Higher natural frequencies<br /> They are multiples of fundamental tone<br /> Instruments designed to resonate <br /> specific overtones<br />49<br />
12. 12. Stringed Instruments<br />Loudness<br /> Resonance of strings to hollow body<br />Pitch<br /> Length, thickness, material, tightness<br />50<br />
13. 13. Wind Instruments<br />Loudness<br /> How much air is blown in<br />Pitch<br /> Length of air column<br />51<br />
14. 14. Percussion Instruments<br />Loudness<br /> How hard the strike<br />Pitch<br /> Size, material, tension of drum head<br />51<br />
15. 15. Acoustics<br />The study of how sounds interact with the environment<br />Reverberation – repeated echoes<br />Curved hard surfaces to direct sound<br />Soft surfaces to absorb sound<br />52<br />