Sound and waves grade 6 pps
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Sound and waves grade 6 pps

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Sound and waves grade 6 pps Sound and waves grade 6 pps Presentation Transcript

  • Sound
  • Overview
    • The Facts of Sound
    • Sound Vocabulary
    • The Ear and Sound
    • Musical Instruments and other uses of Sound
    • Other types of waves
  • The Facts
    • Sound …
    • … is a form of energy produced & transmitted by vibrating matter
    • … travels in longitudinal waves
    • … travels faster through solids than liquids or gases
  • Sound waves travel faster through solids because there are more particles close together to transfer the energy. Sound waves and
  • Speed of Sound
    • Medium (Matter) Speed m/sec
    • gas air (0 o C) 331
    • air (20 o C) 343
    • water (25 o C) 1493
    • liquid sea water 1533
    • iron 5130
    • copper 3560
    • solid glass 5640
    • diamond 12000
  • Vibration
    • Very fast, repeated backward and forward movement of particles of matter
    • For example, the vibration of the tuning fork creates pure sound.
    • The hammer hits the nail and the particles vibrate making noise.
  • Waves transport energy without moving matter Watch the 3 red dots You will see them vibrate , but not move with the wave to the end. All the particles are vibrating but stay fixed
  • Sound Waves
    • Alternating areas of high and low pressure in the air (compressions and rarefactions)
  • Sound Waves
    • ALL sound is carried through matter as sound waves. In a vacuum there are no particles so sound cannot travel.
    • Alternating areas of high and low pressure in the air (compressions and rarefactions)
  • Sound Waves
    • Because sound waves need particles to be transmitted they are mechanical waves
    • ALL sound is carried through matter as sound waves. In a vacuum there are no particles so sound cannot travel.
    • Alternating areas of high and low pressure in the air (compressions and rarefactions)
  • Sound Waves
    • Sound waves move out in ALL directions from a vibrating object.
    • Because sound waves need particles to be transmitted they are mechanical waves
    • ALL sound is carried through matter as sound waves. In a vacuum there are no particles so sound cannot travel.
    • Alternating areas of high and low pressure in the air (compressions and rarefactions)
  • Compression Where particles are pressed together as the sound wave moves through matter.
  • Compression
    • Where particles are pressed together as the sound waves move through matter
    • For example,
      • a wave travels through the springs just like sound waves travel through the air
      • the places where the springs are close together are like compressions in the air.
    compression
    • Compressions - The close together part of the wave.
    • Rarefactions - The spread-out parts of a wave.
    • Compression Wave = Longitudinal Wave
  • Longitudinal Wave (Compression Wave) Each wave particle vibrates back and forth in the same direction of the wave.
  • Sound waves covered till now:
    • States of matter (solid, liquid, gas)
    • Speed of sound through matter
    • No sound in a vacuum
    • Vibration
    • Compression + Rarefaction
    • Longitudinal waves
    • Remember that ….
  • Waves transfer energy without moving matter. Frequency= waves/time If you watch the 3 red dots you will see them vibrate, but not move with the wave to the end.
  • Wavelength & Frequency
    • Wavelength is the distance between one part of a wave and the same part of the next wave
    • Frequency is the number of waves passing a point in a certain tme
    • Many waves = high frequency
    • Few waves = low frequency
  • Pitch = Frequency
    • How high or low a sound is
    • Pitch depends on the frequency of a sound wave
    • For example,
    • Low pitch
    • Low frequency
    • Longer wavelength
    • High pitch
    • High frequency
    • Shorter wavelength
  • Frequency is measured in Hertz
    • For example:
    • If 20 waves are made per second, then the frequency is 20 cycles per second =
    • 20 Hertz
    • Hz
  • 20 Hz – 20,000 Hz The human ear can only hear sounds between 20Hz and 20,000 Hz (Frequency/Pitch) Below 20 Hz is called infrasound Above 20,000 Hz is called ultrasound
  • Ultrasound sound waves with frequencies above the normal human range of hearing. Sounds in the range from 20,000-100,000Hz Infrasound sounds waves with frequencies below the normal human range of hearing. Sounds in the 0.001 - 20Hz range
  • The Ear
    • Sounds reach our ears through vibrating air particles
    • Our ears capture sound waves and turn them into signals that go to our brains
    • Sound waves move through 3 parts of the ear; outer ear , middle ear , + inner ear
  • The Human Ear
  • Amplitude is the maximum distance the particles in a wave vibrate from their rest positions.
  • Amplitude = loudness
    • The intensity of a sound decreases as you move away from a sound. The sound is softer.
    • As the source of a sound comes closer the sound becomes louder, more intense
    • A loud sound has a high amplitude
    • A soft sound has low amplitude
    soft loud
  • Amplitude = loudness
    • The volume or loudness of sound is measured in decibels
    • dB
  • Loudness of Sound in Decibels Sound Loudness (dbs) Hearing Damage Average Home 40-50 Loud Music 90-100 After long exposure Rock Concert 115-120 Progressive Jet Engine 120-170 Pain
  • Sound and Instruments
    • Different musical instruments create different sound vibrations
    • Wind instruments by blowing and vibrating the air e.g. flute, saxophone, organ
    • String instruments by touching and vibrating the strings e.g. guitar, violin, piano
    • Percussion instruments by hitting a surface e.g. drums, cymbals, triangle
  • Sound and Instruments
    • Instruments can be played at different pitches (musical notes) by changing the lengths of different parts.
    • For example,
    • Another way to make different pitches is to change the thickness of the material that vibrates.
    A trombone’s mute absorbs some of the sound waves produced, so a different sound is made.
  • Sonar
    • Sonar uses reflected sound waves (echoes) to find objects in water or air
    Animals use sonar or echo location to find their prey (food); these sounds have such a high pitch or frequency that the human ear cannot hear them Humans use sonar to locate or find objects
  • Ultrasound (above 20,000 Hz) Ultrasound waves are used in medicine They are also reflected sound waves
  • Other types of waves
    • Remember sound waves are longitudinal and mechanical
    • Other waves are transverse, electromagnetic and water waves
  • Transverse waves wave particles vibrate in an up-and-down motion.
  • Transverse waves
    • Crests - Highest part of a wave
    • Troughs - The low points of the wave
  • Electromagnetic waves
    • Electromagnetic waves travel as transverse waves
    • Electromagnetic waves CAN travel through a vacuum
    • Light, microwaves, x-rays, and TV and radio transmissions are all examples of electromagnetic waves
  • Water Waves
    • The blue surface particles move in a clock-wise direction
  • Wave concepts covered in this power point:
    • Sound Waves
    • States of matter (solid, liquid, gas)
    • Speed of sound through matter
    • No sound in a vacuum
    • Vibration
    • Compression + Rarefaction
    • Longitudinal waves
    • Wavelength
    • Frequency = Pitch
    • Hertz Hz
    • 20 – 20,000 Hz
    • Ear ( outer, middle, inner ear)
    • Amplitude = Loudness = Volume
    • Decibels dB
    • Sonar
    • Ultrasound, infrasound
    • Other waves
    • Transverse waves
    • Crests
    • Troughs
    • Electromagnetic waves
    • Water waves
  • That’s all folks!