Figure shows a loudspeaker cone oscillating to produce sound waves:

CBSE Class 9 CBSE Class 9 Science
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Figure shows a loudspeaker cone oscillating to produce sound waves:

  1. As the sound wave passes a point, it produces regions of higher and lower pressure. State the names of these regions.
  2. Describe how the movement of the loudspeaker cone produces these regions of different pressure.
  3. State the effect on the loudness and pitch of the sound from the loudspeaker when
  • the amplitude increases but the frequency of the sound stays the same,
  • the amplitude stays the same but the frequency increases.

Answer:

  1. Regions of higher pressure : Compressions Regions of lower pressure Rarefactions.
  2. Production of regions of higher pressure : when the loudspeaker cone moves forward, i.e., in the direction of propagation of wave, it pushes the layer of air closer. This air layer pushes the next air layer, and process goes on. In this way, the layers of air near the cone are compressed to form a compression, which is a region of higher pressure.
    Production of regions of lower pressure: when the cone moves backward, i.e., away from direction of propagation of wave, it leaves a region of low pressure and the air layers move apart to form a rarefaction.
  • Loudness increases as greater the amplitude of sound waves, louder the sound will be pitch remains same.
    Loudness remains same.
  • Pitch increases as the pitch of a sound is directly proportional to its frequency.
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