Wave motion and velocity of sound wave

Mechanical wave
 The waves which require a material medium for their propagation are known as mechanical waves. e.g. sound waves, waves in the string, etc.

 Electromagnetic wave
 The wave which does not require a material medium for its propagation is known as an electromagnetic wave. e.g. lightwave, x-rays, y-rays, etc. 

Transverse wave
Particles of the medium vibrate perpendicular to the direction of propagation of waves. e.g. lightwave, heatwave, all electromagnetic waves, waves in a string. 

• For transverse wave medium requires shear modulus, hence medium must be rigid.
 • Shear modulus of liquid and gas is zero.
• Only energy is transferred.
 • It can be polarized.

 Longitudinal wave
The particle of the medium vibrates in the direction of propagation of the wave.
• It cannot be polarized.
• Mechanical waves transfer energy and momentum.
• In longitudinal wave density of medium changes. 

Sound wave
 i. Material medium is required for their propagation.
ii. Sound waves are longitudinal in nature.
iii. Sound travels in rocks in the form of longitudinal and transverse waves both.
iv. Speed of sound in air at NTP is 332 m/sec.
 v. Sound waves cannot be polarized.
vi. Sound wave is audible between 20 Hz to 20 kHz.