Question

The sounds that cannot be heard by humans are
(A). inaudible sounds
(B). infra sounds
(C). ultrasounds
(D). all of the above

Answer 1

Hint: Humans hearing depends on the pitch of the sound and humans can hear only certain frequency sounds of the range 20 Hz – 20kHz. All the other frequencies which are below and above this frequency are inaudible.

Complete step by step answer:
Sound is a wave that travels through the medium by the vibration of molecules in it. Therefore, it always requires a material medium to travel.
Hearing range is the range of frequencies that can be heard by humans or other animals,
The human ear has a perceived frequency range of 20 Hertz to 20 kHz which is called audible sound. Any frequency below 20 Hz is called infrasound and any frequency above 20 kHz is called ultrasound. These are inaudible sounds.
So, we cannot hear inaudible sounds, ultrasound, and infrasound.
Thus, the correct option is D- all the above as all the options are correct and not audible sounds.

Additional information:
We hear through our ears and shape of the outer part of the ear is like a funnel, when sound enters it, it travels down a canal and reaches the eardrum
Sound vibrations make the eardrum vibrate then these vibrations are sent to the inner ear and then this signal goes to the brain and we hear.
Sound waves lose energy as they travel that is why we hear sounds of near distance. And human middle ear apparatus makes it impossible to hear ultrasound or infrasound.

Note: Students make mistakes by opting one among the options A, B and C as they all are right answers. Infrasound and ultra sounds are subsets of inaudible sound. Therefore, option D is an accurate one which states all the options are correct.