Sound Or Can You Hear Me Now Sound
- Slides: 8
Sound Or Can You Hear Me Now?
Sound in General • Caused by mechanical vibration • Mechanical Wave • Longitudinal Wave – Dilations or Rarefactions – Compressions • V=fl, T=1/f, E ~A 2 • Videos of moving sound waves
Human Hearing • Frequency = pitch • Amplitude = Loudness • Intensity (power/area) – Human hearing is logarithmic – d. B scale – Intensity = P/4 pr 2
Speed of Sound • Speed of sound is determined by the medium – 340 m/s for dry air at 20 deg C – Increases with density of material – Increases with temperature – Increases with humidity • True also of distance
Beats • Interference phenomenon occuring when two sound frequencies are sounded together • Variation in loudness • # Beats = f 1 – f 2 http: //library. thinkquest. org/19537/ Inter. html
Check Question • A piano tuner tightens a piano string and hears more beats than before when sounded against his tuning fork. What should the tuner do in order to get the piano in tune? A. Continue tightening the string B. Loosen the string C. Do nothing the piano is in tune
Other Sound Phenomenon • Interference – Phasing of speakers – Boxing a speaker • Doppler Shift • Reflection – Echo Problems use t/2 • Thunder Problem – Poltergeist Scene use t
Transmissionability • Ability of material to transmit sound with small loss in amplitude • Denser materials have higher transmissionability • The Indian Trick • The Train Trick • Whale Tricks
