Factors affecting the speed of sound

  1. Temperature: The speed of sound is directly proportional to the square root of the temperature. So the higher the temperature, the greater the speed of sound. This is why sound travels faster on sunny days than on colder days.
  2. Wind: The speed of sound increases in the same direction as the wind blows and decreases if the sound travels in the opposite direction of the wind.
  3. Density of the earth medium: The speed of sound is inversely proportional to the square root of the density D. Density means mass per unit volume of a substance. So the higher the density of a medium, the lesser the speed of sound.

Echo: This is a reflection of sound. When sound wave strikes a smooth surface, the sound will be sent back, so that it is being heard twice.


Uses of echo

  1. It is used for determination of speed of sound
  2. It determines distance of objects
  3. It is used in oil and gas exploration-
  4. It is used to detect flaws in metals pipes
  5. It is used in medical ultrasound


The Human Ear

This sense organ responds to stimulus of sound. It is made up of outer ear, middle ear and inner ear


The Outer Ear: The pinna collects sound waves and directs them to the ear canal. This passes the vibration to the eardrum, which increases the vibration and sends it to the middle ear. Here is a small air -filled chamber. It is made up of three tiny soft bones called ossicles, held in place by muscles. These bones in the ear are called hammer, incus and stapes. These bones vibrate and send the sound into the inner ear. The inner ear contains a complex of bony passageways filled with fluids called perilymph and endolymph. The vibrations gets to the cochlea and the semi-circular canals .The sound is then conveyed by nerves to the brain for interpretation.



  1. Explain echo
  2. Explain factors that affect speed of sound
  3. Which part of the ear maintains balance

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