Factor affecting the velocity of sound
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| Velocity of a wave |
Introduction : We are now aware of velocity of a mechanical wave explained by newton's and laplace. When the wave travel from one medium to another, the velocity changes as well as wavelength changes but frequency remains same. Theoretically, the velocity of the wave is same in same medium but practically it changes with changes in some atmospheric factor. We are going to discuss the factors in details.
Effect of pressure on velocity of a sound : When sound travels in an air medium, then the change in pressure at constant temperature of the medium has no effect on velocity of the sound.
Let us understand it mathematically,
According to Laplace's
According to boyle's law at constant temperature ,Pressure remains constant.
From equation (1) we can conclude that the change in pressure at constant temperature of the medium has no effect on velocity of the sound.
Effect of temperature on velocity of a sound : When sound travels in an air medium, then the change in temperature of the medium result in change in velocity of the sound.
mathematically,
Let V and V0 be the velocity of sound at 0°C and t°C respectively.
From Laplace equation,
From equation (A) we can conclude that velocity of sound in air is directly proportional to square root of its absolute temperature.
Effect of humidity on velocity of a sound : When sound travels in an air medium, then the change in humidity of the medium result in change in velocity of the sound.
mathematically,
Let Vm and Vd be the velocity of sound in moist and dry air
respectively. 0°C and t°C respectively.
From Laplace equation, ρm and ρd be the densities of moist and dry air
respectively.
Equation (A) concludes that speed of sound in moist air is greater than speed of sound in dry air. Thus speed of sound increases with increase in moisture.
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