• Speed of Sound

    Sound is a form of energy, just like electricity, heat or light. When we strike a bell, it makes a loud ringing noise. If we put our finger on the bell after we have struck it. We feel that it shaking. This movement or shaking, i.e. the to and fro motion of the body is termed as Vibration. The sound moves through a medium by alternately contracting and expanding parts of the medium it is travelling through.

    The speed of sound is the distance which is travelled per unit time by any sound wave which can be measured. Speed of sound depends on the nature of material through which it travels.  In general, sound travels slowest in gases, faster in liquids and fastest in solids. Speed of sound increases with the rise in temperature & humidity of air.  

    Speed of Sound in Different Media at 25 0C

    S.No.

    State

    Material

    Speed of Sound

    1

    Solid

    Aluminium
    Nickel
    Steel
    Iron
    Brass
    Glass (Flint) 

    6420
    6040
    5960
    5950
    4700
    3980

    2

    Liquid

    Water (Sea)
    Water (distilled)
    Ethanol
    Methanol 

    1531
    1498
    1207
    1103

    3

    Gas

    Hydrogen
    Helium
    Air
    Oxygen
    Sulphur dioxide 

    1284
    965
    346
    316
    213

     

     

    Effect of Temperature on Speed of Sound in Air

    Temperature (0C)

    Speed of sound (m/s)

    Temperature (0C)

    Speed of sound (m/s)

    35

    351.88

    0

    331.3

    30

    349.02

    −5

    328.25

    25

    346.13

    −10

    325.18

    20

    343.21

    −15

    322.07

    15

    340.27

    −20

    318.94

    10

    337.31

    −25

    315.77

    5

    334.32

    −30

    312.58

     

     

    Comparison of Speed of Sound and Light

    Sound travels in air at 20 ºC at the speed of 344 m/s while light travels at the speed of (3 x 108 m/s).

    Examples:

    1. In the rainy season, the flash of lightning is seen first and the sound of thunder is heard a little later though both are produced at the same time.

    2. In the game of cricket, the ball is seen to hit the bat first and the sound of hitting is heard a little later.

    3. If a gun is fired from a distance, we see the flash of gun first and the sound of gun shot is heard a little later.

    4. In villages, when clothes are washed by beating them on the stone, the clothes hitting the stone is seen first and the sound of hitting is heard a little later.

    Sonic Boom: Some aircrafts, bullets, rockets etc. have ‘supersonic speed’. Supersonic refers to the speed of an object which is greater than the speed of sound and it produces extremely loud sound waves called ‘shock waves’ in air. Sonic boom is an explosive noise caused by shock waves. It emits tremendous sound energy which can shatter the glass panes of windows.