It’s a world of sound! Sound is everywhere around us- in the music we hear, the movies we watch and the conversations we have. However, have you ever stopped to ponder over the science behind sound? If you have, then read on to find out-
What is Sound?
Sound is a form of energy that produces the sensation of hearing in our ears.
Although we do not see sound coming to us, yet, sound reaches our ears in the form of waves formed due to the vibrations of particles of the medium. The waves carry the mechanical energy of the vibrating particles with them so as to produce a sensation of hearing in our ears. Sound is produced when a body vibrates.
Do you know that sound is also a form of energy? Mechanical energy is required to start vibrations in a body producing sound. The vibrations of the body are transmitted through the medium in the form of waves from that point to the next and so on. These waves, on reaching our ears, produce vibrations in the ear drum which are perceived as sound by us. Thus, sound is a form of energy.
How Does Sound Propagate?
Sound propagation requires a material medium. Sound produced by a vibrating body travels from one place to the other through the mechanical vibrations of the medium particles in form of waves. Thus a material medium is necessary for the propagation of sound from one place to another.
Requisites of the medium – The medium required for propagation of sound must possess the following three properties:
1. The medium must be elastic so that its particles may come back to their initial positions after displacement on either side.
2. The medium must have inertia so that its particles may store mechanical energy.
3. The medium should be frictionless so that there is no loss of energy in the propagation of sound through it.
Sound can propagate not only in gases, but also in solids and liquids. Some materials such as air, water, iron etc. can easily transmit sound through them from one place to another. On the other hand, blanket, thick curtains etc., absorb most of the sound incident on them and transmit or reflect only a small fraction of it.
Sound cannot travel in vacuum. There is no medium on the moon. Therefore, on the moon, one cannot hear the sound produced by the others.
Light does not require any material medium for its propagation and it can therefore propagate through vacuum as well.
Propagation of Sound in a Medium-
When a source of sound vibrates, it creates a periodic disturbance in the medium near it. The disturbance then travels in the medium in form of waves.
Sound travels in air in the form of longitudinal waves. Actually the longitudinal waves can be produced in solids, liquids as well as gases. At compressions, the density and pressure of the medium is maximum, while at rarefaction the density and pressure of the medium is minimum.
Wavelength of Sound Waves-
The distance travelled by a sound wave in one time period of vibration of particle of the medium, is called its wavelength.
In a longitudinal wave, the distance between two consecutive compressions or between two consecutive refractions is equal to one wavelength, while in a transverse wave, the distance between two consecutive crests or between two consecutive crests or between two consecutive troughs is equal to one wavelength.