How does our ear work?

The ears are the sense organs that help us in hearing a sound. So, we hear through our ears. We will now describe the construction and working of a human ear briefly.

The shape of the outer part of the ear (which we see outside the head) is like a funnel. The outer part of the ear is called 'pinna' and it is attached to an about 2 to a 3-centimeter long passage called 'ear canal'. A thin, elastic, and circular membrane called 'eardrum' is stretched tightly at the end of the ear canal. There are three small and delicate bones called hammer, anvil, and stirrup in the middle part of the ear which are linked to one another. One end of the hammer touches the eardrum and its other end is connected to the second bone anvil. The other end of the anvil is connected to a third bone called stirrup. And the free end of the stirrup touches the membrane over the oval window. The inner part of the ear has a coiled tube called a window. The cochlea is filled with a liquid. The liquid present in the cochlea contains nerve cells that are sensitive to sound. The other end of the cochlea is connected to the auditory nerve which goes into the brain. Please note that the three tiny bones in the middle part of the ear act as a system of levers and amplify sound vibrations coming from the eardrum before passing them on to the inner part of the ear (cochlea).

We will now describe the working of the ear. The sound waves (coming from a sound-producing body are collected by the pinna of the outer part of the ear. These sound waves pass through the ear canal and fall on the eardrum. When the sound waves fall on the eardrum, the eardrum starts vibrating back and forth rapidly. The vibrating eardrum causes a small bone hammer to vibrate. From the hammer, vibrations are passed on to the second bone 'anvil', and then to the third bone 'stirrup'. The vibrating stirrup strikes on the membrane of the oval window and passes the amplified vibrations to the liquid in the cochlea. Due to this, the liquid in the cochlea begins to vibrate. The vibrating liquid of the cochlea sets up electrical impulses in the nerve cells present in it. These electrical impulses are carried by the auditory nerve to the brain. The brain interprets these electrical impulses as sound and we get the sensation of hearing.

Why Sound travels slower than light.

The speed of sound in air is about 340 m/s and the speed of light in air is 300,000,000 m/s. This means that sound travels at a slow speed but light travels much, much faster than sound. In fact, the speed of light is very great as compared to the speed of sound. So, though the sound may take a few seconds to travel a distance of a few hundred meters, the light will take practically no time to reach a distance of even a few kilometers. We will now give an observation from our everyday life which is based on the low speed of sound in the air but very high speed of light. It is a common observation that in the rainy season, the flash of lightning is seen first and the sound of thunder is heard a little later (though both are produced at the same time in clouds). Due to the very high speed of light, we see the flash of lightning first and it is due to the comparatively low speed of sound that the thunder is heard a little later. We will now describe the organ of hearing sound called 'ear'.