Sound Class 9

📝 Sound 

Introduction 

Sound is a form of energy that produces a sensation of hearing in our ears. When you clap, a sound is produced. Can you produce sound without utilising your energy? Which form of energy did you use to produce sound? In this chapter, we are going to learn how sound is produced and how it is transmitted through a medium and received by our ears.

Production of Sound 

Sound is produced when something vibrates. The matter or substance through which sound is transmitted is called a medium. It can be solid, liquid or gas. Sound moves through a medium from the point of generation to the listener. When an object vibrates, it sets the particles of the medium around it vibrating. The particles do not travel all the way from the vibrating object to the ear. A particle of the medium in contact with the vibrating object is first displaced from its equilibrium position. It then exerts a force on the adjacent particle. As a result of which the adjacent particle gets displaced from its position of rest. After displacing the adjacent particle the first particle comes back to its original position. This process continues in the medium till the sound reaches your ear.

Sound Waves 

A wave is a disturbance that moves through a medium when the particles of the medium set neighbouring particles into motion. They in turn produce similar motion in others. The particles of the medium do not move forward themselves, but the disturbance is carried forward. This is what happens during the propagation of sound in a medium, hence sound can be visualised as a wave. Sound waves are characterised by the motion of particles in the medium and are called mechanical waves.

Nonmechanical waves 

Waves that do not need a material medium to propagate are called non-mechanical waves. For example, light from the sun travels in space through vacuum before reaching the earth. Light, radio waves are non-mechanical waves. 

Mechanical waves 

Waves that need a material medium to propagate are called mechanical waves. Sound waves are mechanical waves