After reading this article you will learn about the mechanism and range of human ear.
Mechanism of Human Ear:
The human ear is the organ that enables the sense of hearing. The ear is considered of 3 parts, which are generally called external, middle, and inner ears parts. The ear canal extends from pinna to the eardrum. The canal itself is approx. oval in cross-section and extends from about 25 mm into the head.
Sound first enters through external canal. The sound then falls on the eardrums, which is not flat but is cone shaped with and included angle of about 120 degrees. The eardrum vibrates under the influence of the incidence of sound waves.
The vibrations then get connected through a series of bones which reduces the amplitude but increases the force upon the inner window which, in turn, transit the waves to liquid borne pressure waves within the circular canal called the cochlea.
The pressure fluctuation within the liquid in the cochlea then excite small nerve cells which are known as hair cells. Each of these hair cells has its own individual nerve and these nerves are connected into the auditory nerve that then goes off to the appropriate brain centre.
Range of Human Ear:
People can hear sound from 16 to 20,000hz, but this range is reduced with other subjective factors. The range of vibrations is below 16hz and infra audible and those above 20,000hz ultrasonic. Some persons can hear frequencies that are not audible to others. Many animals (e.g. dogs) can hear sounds inaudible to the human ear.
Human Ear is known to be sensitive to extremely wide range intensity from 0 to 80dB. Here 0dB is the threshold of hearing while 140dB is the threshold pain. By threshold, it implies the lowest intensity at which stimulus gets perceptible. Some people feel discomfort even with sound of 85dB whereas most do not feel discomfort with sound of 115dB. Pain is usually felt at 140dB.
Ordinary talk or discussion is having the frequency range of 30—60dB while noise produced by a jet plane at take off may exceed 160dB. The effect on man depends upon the frequency or the pitch of the sound. The sound pressure level has been regarded to be of greater loudness for higher pitched than for the lower pitched sound.