# Sound and Vibrations

Sound and Vibrations:

How are you acquainted with the lunch timings at school? Generally with the help of a ringing bell that sounds. In the same way, if your friend is standing at the door knocks, you come to know that he is standing at the door. A person can be inquisitive about what happens when a bell rings or when someone knocks the door? In simple terms, we can say that a sound is produced, that we hear and then we respond back suitably. But have you ever thought what is sound? How is it produced? Let us try and figure out the answer or such questions.

A sound is a form of energy, and this energy comes from vibrations. These vibrations are responsible for creating sound waves which then move through elastic mediums such as air, water, etc. and then finally reaches our ears. Elastic mediums are those mediums which can change in shape as a result of some deforming force. Such mediums resume their original shape when the same force is removed. Thus, a sound wave needs a medium for its propagation. Now, let me ask you a simple question- how is the sound of any musical instrument different from noise? Music is produced by periodic vibrations which have a regular wave pattern whereas noise is generated by irregular vibrations, which has an irregular wave pattern. For example, a sound generated by a moving vehicle. Thus, noise can be easily differentiated from a useful sound.

Let us go in a bit detail about sound waves. We know that sound waves are produced as a result of vibrations. But how are these caused? Sound waves can be considered as pressure waves which are made up of compressions and rarefactions. Compression happens when the medium particles are forced or pressed together. Rarefaction occurs when the particles get extra space and thus are allowed to expand. Now, as the particles are moved from their rest position, they exert a force on the adjacent particulate matter and thus pass the energy.

Have you ever wondered how a human voice is produced? It is also a type of sound. A human sound is by the vibrations of the vocal chords inside the larynx. These vibrations then propagate through the air and reach other person’s ears. These sound waves then enter the ear canal of the other person and cause the eardrum to vibrate. But have you ever wondered why do we have two ears and not just one? We know that ears transmit sound waves to the brain and thus having an ear on each side of the head make it easier for us to determine where the sound is coming from. Having two ears provides better sound quality and also helps us to hear the sound clearly from both directions.

The sound has different speed in different mediums. It depends on medium properties. In general, sound travels faster in solid mediums compared to liquid and gaseous mediums. In the same way, the speed of light is faster in liquid medium as compared to gaseous medium.

#### Practise This Question

The lowest level of organisation among eumetazoans is

 NCERT Related Articles NCERT Solutions for Class 12 NCERT Solutions for Class 11 NCERT Solutions for Class 10 NCERT Solutions for Class 12 Maths NCERT Solutions for Class 11 Maths NCERT Solutions for Class 10 Maths NCERT Solutions for Class 12 Physics NCERT Solutions for Class 11 Physics NCERT Solutions for Class 10 Science NCERT Solutions for Class 12 Chemistry NCERT Solutions for Class 11 Chemistry NCERT Solutions for Class 6 NCERT Solutions for Class 12 Biology NCERT Solutions for Class 11 Biology NCERT Solutions for Class 6 Maths NCERT Solutions for Class 9 NCERT Solutions for Class 8 NCERT Solutions for Class 6 Science NCERT Solutions for Class 9 Maths NCERT Solutions for Class 8 Maths NCERT Solutions for Class 4 NCERT Solutions for Class 9 Science NCERT Solutions for Class 8 Science NCERT Solutions for Class 4 Maths NCERT Solutions for Class 5 NCERT Solutions for Class 7 NCERT Solutions for Class 7 Maths NCERT Solutions for Class 4 Science NCERT Solutions for Class 5 Maths NCERT Solutions for Class 7 Science NCERT Solutions NCERT Books NCERT Solutions for Class 5 Science