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SOUND

SOUND. SOUND. KEY TOPICS NATURE OF SOUND AUDIO SPECTRUM RESONANCE & FORCED VIBRATION INTERFERENCE REFLECTION & REFRACTION. SOUND. SOUND ANIMATION DEMO. SOUND. LONGITUDINAL WAVES ON A SLINKY DEMO. SOUND.

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SOUND

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  1. SOUND

  2. SOUND • KEY TOPICS • NATURE OF SOUND • AUDIO SPECTRUM • RESONANCE & FORCED VIBRATION • INTERFERENCE • REFLECTION & REFRACTION

  3. SOUND • SOUND ANIMATION • DEMO

  4. SOUND • LONGITUDINAL WAVES ON A SLINKY • DEMO

  5. SOUND • SOUND IS THE COHERENT VIBRATIONS OF ATOMS OR MOLECULES IN SOLIDS, LIQUIDS AND GASSES. • INCOHERENT VIBRATIONS ARE CALLED HEAT.

  6. ACTIVITY • SOURCES OF SOUND • SOUND MEDIA

  7. SOUND SOUND SPECTRUM INFRASOUND < 20 HZ • AUDIBLE SOUND > 20 HZ • AND < 20 KHZ DEMO ULTRASOUND >20 KHZ

  8. SOUND • The PHET simulator “SOUND” can be used to demonstrate sounds up to 1kHz.

  9. ACTIVITY • HARRY’S SOUND SORT • SORTING SOUNDS

  10. SOUND • THE SPEED OF SOUND IN AIR IS APPROXIMATELY • 330 m/s • 1000 ft/s DEMO • THIS IS ALSO DESIGNATED MACH 1 • THE SPEED DEPENDS ON TEMPERATURE, PRESSURE AND HUMIDITY

  11. SOUND • IF ONE SEES A LIHTNING FLASH AND 15 SECONDS LATER, HEARS THE THUNDER, THEN THE DISTANCE TO THE FLASH IS _______ MILES. • A. 3 • B. 15 • C. 1 • D. 30

  12. RESONANCE • VIBRATING AT A NATURAL FREQUENCY • ENERGY CAN BE TRANSFERRED EFFICIENTLY TO A VIBRATING OBJECT VIA RESONANCE. DEMO

  13. RESONANCE • The Tacoma Narrows bridge collapse is one of the most dramatic examples of resonance. • DEMO

  14. RESONANCE • RESONANCE IS USED TO PRODUCE MUSICAL NOTES WITH A DEFINITE FRQUENCY. • EXAMPLES OF VIBRATING OBJECTS • STRINGS • AIR COLUMNS • SURFACES (DRUMS) DEMO

  15. ACTIVITY • Singing Rod • Wine Glass • Corrugated Horn

  16. ACTIVITY • RUBBER BAND GUITAR • CHANGES IN FREQUENCY • CLIP NOTES

  17. FORCED VIBRATION • VIBRATING AT A NON-RESONANT FREQUENCY • IT IS OFTEN APPLIED TO THE AMPLIFICATION OF SOUND

  18. ACTIVITY • CHICKEN CLUCKER

  19. MUSICAL SOUNDS • DIATONIC SCALE • POPULAR IN EARLY WESTERN EUROPEAN MUSIC (VOCAL) • AN OCTAVE CONTAINED THE FAMILIAR PATTERN OF • DO RE ME FA SO LA TI DO • C D E F G A B C • THE DO AT THE END OF THE OCTAVE HAD TWICE THE FREQUENCY OF THE DO AT THE BEGINNING • FREQUENCIES ARE WHOLE NUMBER RATIOS OF EACH OTHER

  20. MUSICAL SOUNDS • EQUITEMPERED SCALE • THE FREQUENCY OF EACH NOTE IS OBTAINED FROM THE NEXT SMALLER NOTE BY MULTIPLYING BY THE TWELTH ROOT OF TWO (1.059463) • EACH OCTAVE HAS THIRTEEN NOTES • THE NOTES ARE • C C# D D# E F F# G G# A A# B C • THE SHARPS ARE THE BLACK KEYS ON A PIANO

  21. ACTIVITY • NOTE BEATERS

  22. SOUND INTERFERENCE • The PHET simulator “SOUND” can be used to show the superposition of sound from two different sources.

  23. BEATS • THE INTERFERENCE OF SOUND FROM TWO DIFFERENT SOURCES • IT IS MOST NOTICEABLE WHEN THE FREQUENCY AND LOUDNESS OF THE SOUNDS ARE SIMILAR • THE BEAT FREQUENY IS CALCULATED BY TAKING THE DIFFERENCE BETWEEN THE TWO FREQUENCIES fb = fl - fs

  24. ACTIVITY • BEATS WITH TWO TUNING FORKS

  25. QUALITY THE QUALITY OF A SOUND IS DETERMINED BY THE INTENSITY OF THE HARMONICS PRESENT.

  26. QUALITY The PHET simulator “FOURIER: MAKING WAVES” can be used to show how the quality can be changed by varying the harmonics present.

  27. PITCH • THE AUDITORY PERCEPTION OF FREQUENCY

  28. REFLECTION OF SOUND • REVERBERATION • RE-REFLECTED SOUND THAT OCCURS IN CONFINED AREAS SO THAT THE REFLECTED SOUND CAN NOT BE DISTINGUISHED FROM THE SOURCE • EXAMPLE - EMPTY ROOM

  29. REFLECTION OF SOUND • ECHO THE SOUND IS THAT NORMALLY REFLECTED OUTSIDE OR IN LARGE ENCLOSED AREAS SO THAT THE REFLECTED SOUND CAN BE DISTINGUISHED FROM THE SOURCE.

  30. SOUND REFRACTION • THE CHANGE IN THE DIRECTION OF TRAVEL OF A SOUND WAVE DUE TO CHANGES IN ITS SPEED. • IT IS OFTEN CAUSED BY TEMPERATURE DIFFERENCES IN THE AIR.

  31. TOYS WITH SOUND • CAN YOU EXPALAIN HOW MUSICAL TOYS OR NOISE MAKERS PRODUCE OR CONTROL SOUND?

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