Sound

Science Class 8 : Chapter 13

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Quick Revision : Sound

  • Sound Production: Sound is produced by vibrating objects.
  • Vibration: Rapid to-and-fro motion of an object.
  • Medium for Propagation: Sound needs a medium (solid, liquid, gas) to travel; cannot travel through vacuum.
  • Human Ear: Sound enters through ear canal, vibrates eardrum, transmitted to inner ear and brain.
  • Amplitude: Maximum displacement of vibrating object; determines loudness.
  • Frequency: Number of oscillations per second (Hz); determines pitch.
  • Audible Range: Humans can hear sounds from 20 Hz to 20,000 Hz.
  • Noise Pollution: Unwanted or excessive sound harmful to health and environment.
  • Larynx: Voice box in humans that produces sound through vocal cord vibrations.
  • Noise vs Music: Music is pleasant, organized sound; noise is unpleasant, irregular sound.

Questions

Chapter Summary : Sound

What You Will Learn: This chapter covers how sound is produced by vibrating objects, propagation of sound through different media, structure and function of human ear, characteristics of sound (amplitude, frequency, time period), difference between noise and music, noise pollution and its harmful effects, and measures to control noise pollution.

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