1 / 18

Sound Pitch Loudness Sound Intensity Level Doppler Effect

Discover the properties of sound waves, intensity levels, and the Doppler effect in physics. Learn about pitch, speed of sound, and bow waves with simulations and examples.

campbellh
Download Presentation

Sound Pitch Loudness Sound Intensity Level Doppler Effect

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Sound Pitch Loudness Sound Intensity Level Doppler Effect Physics Mrs. Coyle

  2. Sound • Sound is a longitudinal mechanical wave. • Compressions(High Pressure) • Rarefactions(Low Pressure)

  3. Speed of Sound • Depends on the medium. • The more elastic the medium the faster sound will travel through it.  • Speed in metals>speed in water>speed in air • Sound can’t travel through vacuum.

  4. Speed of Sound in Air v = 331 + 0.6 T ( in meters/sec) • T is the temperature in 0C. • In higher humidity, sound will travel faster.

  5. Properties of Sound • Reflection (Echo) • Refraction • Interference • Diffraction

  6. Pitch: the frequency of a sound wave. • Musical notes have a given pitch. • The note C has a frequency of 327Hz. • When two notes differ by a ratio of 2:1 they are one octave apart. • What would be the next higher C? (Ans:654Hz)

  7. Bow (Shock) Waves When the speed of a moving sound source is greater than the speed of the wave, a pressure ridge builds similar to the wave created by the bow of a ship. physlet animation

  8. Sonic Boom • When the pressure ridge of a bow wave of a jet passes over an observer on the ground, the observer experiences a sonic boom.

  9. Doppler Effect • The change in a wave's perceived frequency due to the motion of either the sound source or the observer.  • It is applicable to any type of wave. • Austrian physicist Christian Doppler (1803-1853). train sound clip Simulations • physlet animation • http://www.walter-fendt.de/ph14e/dopplereff.htm

  10. The Doppler Effect http://www.physicsclassroom.com/Class/sound/u11l3b.cfm

  11. Doppler Effect Detected Frequency, (fD) fD = f (v±vo) v±vs f : frequency of source v : speed of sound vo : speed of observer (+)when observer moving towards source vs: speed of source (-)when source is moving towards observer

  12. Example 1 An ambulance is approaching a stationary observer. The siren of the ambulance emits a frequency of 480Hz and the speed of the ambulance is 50km/h(=13.88m/s). What frequency will the stationary observer hear when the ambulance is approaching? Assume T=20oC.Answer: fd = 500Hz

  13. Sound Intensity (I) I = (Power transmitted by the Wave)/Area • Threshold of human hearing: Io =1 x 10-12 Watts/m2 • Threshold of Pain: IP= 1 Watts/m2

  14. Sound (Intensity) Level • A measure of our perception of the loudness of the sound. • Unit: decibel(dB)

  15. Sound (Intensity) Level, (decibel) b= 10 log I , unit for b is dB (decibel) I0 The decibel compares the sound intensity (I), to Io (1 x 10-12 Watts/m2) , the threshold of human hearing. Remember: log(10x )= x

  16. Examples of Sound Intensity Levels • jet plane taking off 140 dB • air raid siren 125 dB • threshold of pain 120 dB • loud rock music 115 dB • ear damage starts 85 dB • busy traffic 70 dB • normal conversation 60 dB • quiet library 40 dB • soft whisper 20 dB • threshold of human hearing 0 dB

  17. Example 2 • What is the sound level (decibel) of a sound of 10-4 W/m2 intensity ? • Answer: 80dB

  18. Example 3 • How many times louder is a quiet library sound (40 dB) compared to a soft whisper (20 dB)? • Hint 1: Property of logs: log(A/B) = logA –logBHint 2: Take the difference in dB and then find (I2 /I1) • Answer: (I2 /I1 )= 100/1

More Related