Sound is a form of energy that is produced by vibrating bodies. But do we hear the sound of every vibrating body? The answer is NO. We have two types of sound – audible sound and inaudible sound. These sounds are categorized on the basis of their frequency ranges
Human ear cannot detect sound frequencies less than 20 vibrations per second i.e. 20 Hz. So any sound below this frequency will be inaudible sound for humans. In the high-frequency range, the human ear cannot detect frequencies above 20000 vibrations per second (20 kHz) and the amplitude of the wave would be dependent on the loudness of the sound. So the frequencies below 20 Hz and above 20 kHz comes under the category of inaudible frequencies. The low-frequency sound which the human ear cannot detect is also known as infrasonic sound. Whereas the higher range inaudible frequency is also known as ultrasonic sound.
Some animals like dogs have the ability to hear sounds having frequencies higher than 20 kHz. The police department uses whistles with frequencies higher than 20 kHz so that only dogs can listen to it. Inaudible frequencies are helpful for many purposes. These are used in many fields like research and medicine. The ultrasound equipment used for tracking and studying many medical problems works at frequencies above 20 kHz.
The human ear can easily detect frequencies between 20 Hz and 20 kHz. Hence, sound waves with frequency ranging from 20 Hz to 20 kHz is known are audible sound. The human ear is sensitive to every minute pressure difference in the air if they are in the audible frequency range. It can detect pressure difference of less than one billionth of atmospheric pressure.
As we grow older and are exposed to sound for a longer period of time, our ears get damaged and the upper limit of audible frequencies decreases. For a normal middle-aged adult person, the highest frequency which they can hear clearly is 12-14 kilohertz.
So from the above discussion, now we know how sound can be differentiated on the basis of the frequency range and its application. To know more about sound, download BYJU’S- the learning app.