Observing the movements of vocal cords during speech in Sound – Class 8 Science Experiment

Chapter Name: Sound

Activity Name: Observing the movements of vocal cords during speech in Sound

Activity Description:

In this experiment, you will observe the movements of the vocal cords during speech. You will ask a friend to raise their neck and place a stretched chocolate wrapper across their mouth. Then, your friend will blow air forcibly on the wrapper in two different ways: once forcefully and once slowly. You will observe the changes in the movements of their throat during these two occasions.

Required Items:

  1. A chocolate wrapper
  2. A willing participant (your friend)

Step by Step Procedure:

  1. Ask your friend to raise their neck slightly.
  2. Stretch the chocolate wrapper across their mouth, ensuring it is taut.
  3. Instruct your friend to blow air on the wrapper forcibly in the first trial.
  4. Observe the movements in their throat during this trial.
  5. Ask your friend to blow air on the wrapper slowly in the second trial.
  6. Observe the movements in their throat during this trial as well.

Experiment Observations:

  1. During the first trial (forceful blowing), the voice box (vocal cords) gets tensed and produces a high sound. In contrast, during the second trial (slow blowing), the vocal cords are close to the normal position of the throat, and they produce a lower sound.


  1. Ensure your friend is comfortable and willing to participate in the experiment.
  2. Use a clean chocolate wrapper to avoid any hygiene issues.
  3. Make sure the wrapper is stretched tightly across the mouth for accurate observations.

Lesson Learnt from Experiment:

The sound produced during speech is influenced by the movements of the vocal cords. Forceful blowing tenses the vocal cords, resulting in a higher pitch sound, while slower blowing relaxes the vocal cords, leading to a lower pitch sound. The sound we produce during speech is a combination of vibrations from the chocolate wrapper and the movements of the vocal cords.

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