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    This is a very informative presentation. It's very basic nature makes it a very handy and valuable resource for use in classroom. Thanks for making it available to the public.
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Transcript

  • 1. SOUND SECONDARY 3 PHYSICS
  • 2. NATURE AND PRODUCTION OF SOUND
    • Sound is…..
    • A form of energy
    • an example of longitudinal wave
    • Produced by vibrating sources placed in a medium. (solid, liquid or gas)
  • 3. The medium of Transmission
    • Any medium that has particles that can vibrate will transmit sound.
    • Solids can transmit sound fastest followed by liquid then air.
    Application: In olden days, people would hear the ground for movement.
  • 4. Effect of Physical Conditions
    • Temperature?
    • Sound travels faster in higher temperatures
    • Humidity?
    • Sound travels faster in high humidity
    • Pressure?
    • Pressure has no effect on speed of sound
  • 5. Determining the Speed of Sound Using Direct Method
    • Observers A and B are positioned at a known distance, s, apart in an open field.
    • Observer A fires a starting pistol.
    • Observer B starts the stopwatch on seeing the flash of the pistol and stops the stopwatch when he hears the sound.
    • The time interval, t, is then recorded.
    • Speed of sound = s/t
    • Repeat the experiment to minimise random errors.
    • A and B exchange positions to cancel the effect of wind on the speed of sound and repeat a few times again.
  • 6. Audible Frequencies
    • The human ear can only hear sounds of frequencies between 20 Hz and 20 kHz.
    • Any sound with frequency higher than 20 kHz is known as ultrasound .
    • Any sound with frequency lower than 20 Hz is known as infrasound .
  • 7. Application of Ultrasound
    • In medical diagnosis
    • Used to obtain images of internal parts of the body. Commonly used in pre-natal examination.
  • 8. Reflection of Sound
    • Formation of Echoes
    • When sound hits a hard surface, it will “bounce” off the surface. The sound that is reflected back to us is called an echo.
  • 9.
    • Reverberations
    • It is the prolonged sound due to the merging of many echoes.
    • The many echoes are produced because sound will be reflected off the different walls in a room.
    Reflection of Sound
  • 10. Uses of Echoes
    • Fishing boats use echoes to detect shoals of fish
    • Measurement of the depth of the ocean
    • War ships use echoes to detect mines
    • Some animals use echoes to detect obstacles. Eg bats
  • 11. Pitch
    • When describing a musical note as ‘high’ or ‘low’, we are actually talking about the pitch of the sound.
    • Frequency affects pitch.
    • High frequency – high pitch
    • Lower frequency – lower pitch
    • Shorter strings or air tunnels have higher frequency.
  • 12. Loudness
    • It is the volume of a sound.
    • Loudness depends on the amplitude of the sound wave.
    • Louder sounds have larger amplitudes and vice versa.
    • It is measured in decibels (dB).