Interaction of Sound with Different Materials

In our daily lives we hear different kinds of sounds coming from different sources like humans, birds, vehicles, televisions, and music systems.


This is because sound can travel through all sorts of materials.



We are able to hear sound as it travels from its source through the air and other materials, riding on invisible waves, until it reaches our ears.


Sound travels about 4.3 times further in water than in air.


This is why whales and other aquatic creatures can use sound waves to communicate over extremely long distances.


Sound also bounces off when it strikes a hard and smooth surface such as the walls of a room.


This is called reflection of sound.



Concrete walls are good reflectors of sound.


If we shout near a suitable reflecting object such as a mountain, the sound of the shout gets reflected, and we hear it again a little later.


The sound which we hear later is called an echo.


Both soft and rough surfaces absorb sound.


Wooden surfaces, carpets, curtains, and clothes are better absorbers than reflectors of sound.


Materials that absorb sound are used in the walls of auditoriums, to prevent reflection of sound.



Sound-absorbing materials are used for soundproofing offices, aeroplanes, hospitals, and factories, to cut down the loud noise.