Question

Which has the higher frequency – ultrasonic sound or infrasonic sound?
A) Ultrasonic sound
B) Infrasonic sound
C) Both are same
D) Can’t say

Answer 1

Hint: Ultrasonic sound refers to the sound waves that have a frequency greater than the audible sound range of humans. On the other hand, infrasonic sound waver refers to sound waves that have frequency lesser than the audible sound range of humans.

Complete step by step answer:
Ultrasonic sound waves are sound waves that are greater in frequency than $20000Hz$ that is, the upper limit of the human hearing range. On the other hand infrasonic sound waves have a frequency lesser than $20Hz$, that is, lesser than the lower limit of the human hearing range. The human hearing range lies between $20Hz$ and $20000Hz$.
Hence, as is evident from the above explanation, the frequency of ultrasonic sound is greater than the frequency of infrasonic sound.
Hence, the correct option is A) Ultrasonic sound.

Additional information:
Some animals can hear well into the ultrasonic and infrasonic sound range. For example dogs can hear infrasonic sounds. Bats use ultrasonic sound waves to locate and catch their prey. They emit ultrasound that is reflected back from the prey. This reflected ultrasound is received by the bat and it gets an idea of the location of its prey. This is very essential for bats as they live in dark places where visibility is less and they have poor eyesight. They rely largely on their hearing for catching prey.

Note: Students can remember which among ultrasound and infrasound has lesser frequency by developing a sort of relation in the sound of the two words. The word ‘infra’ in infrasound is a bit similar to the word ‘inferior’ which means ‘lesser in some ability’. Hence, students can relate that ‘infrasound’ is ‘inferior’ to ultrasound in terms of its frequency and thus has a lesser frequency than the latter.