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SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY
For FULL presentation click HERE >> www.warnescience.net
SOUND
K Warne
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Sound
• Think of how a drum m...
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Sound
• All sounds start with...
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The speed of Sound
speed = di...
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Experiment to measure the spe...
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Measuring the speed of Sound
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Measuring the speed of Sound
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Practical Write Up
Aim - Stat...
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Practical Write Up
Conclusion...
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Transmission of Sound
• Sound...
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Resonance
• All objects posse...
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Characteristics of Sound
• Re...
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Refraction of Sound
• Sound t...
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Sound Volume
Soft
Sound
The v...
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Sound Pitch
High
Pitch
Sound
...
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What is a Decibel…Practically...
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How Loud?
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Ear
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Ultrasound
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Sound

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A set of slides created to teach Sound to learners at Bishops Diocesan College in Cape Town.

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Transcript of "Sound"

  1. 1. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net SOUND K Warne
  2. 2. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Sound • Think of how a drum makes a noise. • All sounds are produced by vibrating objects.
  3. 3. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Sound • All sounds start with a vibration. • The vibrating object causes compresses and stretches out (rarifies) the air around the object. • These pressure fluctuations then spread out from the object in three dimensions. High Pressure Compression Low Pressure Rarefaction Vibration Waves spread out in three dimensions
  4. 4. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net The speed of Sound speed = distance time x t = time taken for sound to travel distance x The speed of sound is the distance covered by a sound wave in one second.
  5. 5. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Experiment to measure the speed of sound Apparatus: – Loud noise - visual! (starter pistol) – Stopwatch, Pencil, notepad – “Clickometer” ( ( ( ( ( ( ( ( (
  6. 6. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Measuring the speed of Sound Time (s) Speed (m/s) Measurements: Distance = …….. m Speed = distance/time AVERAGE SPEED m/s Write up: Aim Theory Apparatus Method Results Analysis Graph Conclusion Evaluation
  7. 7. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Measuring the speed of Sound Time (s) Speed (m/s) 0.9 169 0.94 161.8 0.3 507 0.45 338 0.6 253.5 0.5 304.2 0.37 411.1 Speed = distance/time AVERAGE SPEED = 306.3m/s Write up: Aim Theory Apparatus Method Results Analysis Graph Conclusion Evaluation
  8. 8. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Practical Write Up Aim - State what you were trying to prove or discover. Theory - Explain (briefly) the underlying theory - include a hypothesis (what you think about the practical) and a prediction ( what you think will happen) if appropriate. Apparatus - list everything used - in detail. Method - Describe what was done in steps and in detail. Results - List all results in a neat table including units. Analysis - Analyze your results to achieve your aim - calculations, graphs etc. All working must be shown clearly. Conclusion - What do your results show - have you achieved your aim. Evaluation - Evaluate the results - are they consistent? If not why do you think they vary? Do any of your results seem anomalous (out) how does this affect the overall result if you ignore it? Are there improvements you could suggest to make your results better?
  9. 9. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Practical Write Up Conclusion - Speed calculated 552 m/s. Evaluation - Our results are not accurate. Actual value 330 m/s. Our percentage error = (error/actual value)x100 = 67% Our speed is too high. • Our distance was calculated twice with and an accuracy of 30cm. • Percentage error (distance) of % error (s) = (error/actual value)x100 (0.30/131)x100 = 2.29 % • Percentage error (time) % error (t) = (error/actual value)x100 (0.05/0.25)x100 = 20 % • Obviously our time measurements are causing the biggest error. This is largely due to the fact that the time measurements are very small (0.3) of a second and so any error is a large percentage of the value being measured. • There is also reaction time delay when starting and stopping the stopwatch - that occurs TWICE in each reading! • As speed is calculated by dividing distance by time and our speed value is too high - our time values must have been too small! • To get more accurate results we need to - - -
  10. 10. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Transmission of Sound • Sound is transmitted as a Longitudinal Wave • It is a series of Compressions & Rarefactions • Solids - more dense - particles closer, Liquids - less dense - greater spaces, gases - least dense - large spaces. • Sound transmitted better in solids, then liquids then gases. • Factors affecting - wind, air pressure Air compressed - high pressure Air rarified - low pressure Vibrating Object • Sound cannot travel through a vacuum. • If there is no air to carry the sound wave there can be no sound. Direction of movement
  11. 11. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Resonance • All objects possess their own natural frequency at which they can vibrate. • Any vibration at that natural frequency, in the same medium, will cause the object to vibrate. 1. Singer generates vibrations at the natural frequency of the wine glass. 2. Sound waves transmit the energy to the glass. 3. The glass begins to vibrate - and can shatter if the volume and frequency are right.
  12. 12. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Characteristics of Sound • Reflection - sound is reflected off surfaces in the same way as other waves. • Reflected sound is called an echo. • Echo location - bats, sonar • Multiple reflections - acoustics - reflected sounds must be absorbed. (curtains or reflecting surfaces.) S = depth Distance = speed x time Depth (s) = distance/2 Distance = 2xs
  13. 13. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Refraction of Sound • Sound travels faster through warm air. • The sound waves refract at night to follow the earths surface. • Sounds can be heard better at night. ground At Night Warm air Cold air ground Daytime Cold air Warm air Sound is refracted away from the earth.
  14. 14. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Sound Volume Soft Sound The volume of a sound wave is determined by the amplitude of the vibration. Small Disturbance – small differences in pressure Large Disturbance – very high and very low pressure Loud sound AirpressureAirpressure Low amplitude - air pressure does not change much. High amplitude - air pressure changes drastically.
  15. 15. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Sound Pitch High Pitch Sound The pitch of a sound wave is determined by the frequency of the vibration. Low Pitch sound AirpressureAirpressure High pitch is caused by high frequency. Low pitch is caused by Low frequency.
  16. 16. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net
  17. 17. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net What is a Decibel…Practically Speaking • The level of sound the ear first begins to recognize (threshold of hearing) has been determined to be .0002 microbars. • The small amount of pressure causes the ear membrane to move less than the diameter of a single atom! • A sound loud enough to begin to create a sensation of pain (threshold of pain) represents a sound pressure that is 3,162,300 times more than the threshold of hearing! These are the limits in our range of hearing. • if we used the microbar to describe sounds, the numbers would be very cumbersome. In addition, it would be difficult to comprehend any comparisons. • Early acousticians came up with a simple method of comparing two sounds. A sound that was perceived to be twice as loud as another was said to be one Bel greater in sound level. • The Bel was used as a unit of comparison. It is not a unit of measure. Its namesake, Alexander Grahm Bell, was a pioneer in the science of audiology (the study of human hearing). • t soon became apparent this unit of comparison was not very useful in describing the difference between similar sounds. A small unit of comparison, the decibel, was established. One decibel (1 dB) is one-tenth of a Bel. Since a decibel is one- tenth of a Bel, then 10 decibels (10 dB) would equal one Bel. In other words, a sound that is twice as loud as another sound could be described as being 10 decibels (10 dB) louder. By definition, one decibel (1 dB) represents the smallest change in volume a human ear can perceive. The average ear, however, can only detect a 3 dB change
  18. 18. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net How Loud?
  19. 19. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Ear
  20. 20. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Ultrasound
  21. 21. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Hi - This is a SAMPLE presentation only. My FULL presentations, which contain loads more slides (with all the gaps filled in) as well as other resources, are freely available on my resource sharing website: www.warnescience.net (paste into your browser if link above does not work) Have a look and enjoy! Keith Warne
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