# Introduction to Mechanical Waves

We know that sound is a form of energy that gives sensation of hearing to our ears. The wave which require material medium for its propagation is called mechanical wave. Since, sound propagates through  a medium, it is a mechanical wave. Sound waves are longitudinal waves that can travel through any medium. When sound propagates, it travels by forming a series of compression and rarefaction. So, there is a change in volume in different marts of the medium. The speed of sound depends upon the properties of the medium.

Velocity of  waves:

The velocity of sound in different medias have different relation. The various relations are given below:

1. Velocity of longitudinal wave in liquid and gas:

$$V = \frac{ \beta }{ \rho }$$

Where, β is the bulk modulus of elasticity of the  medium and ρ is the density of the medium  i.e., liquid or gas.

2. Velocity of longitudinal wave in solid rod:

$$V = \frac{ \gamma}{ \rho }$$

Where, γ is the Young’s modulus of elasticity and ρ the density of the medium.

3. Velocity of sound wave:

$$V = \frac{ E}{ \rho }$$

Where, E is the modulus of elasticity and  ρ the density of the medium.

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