Answer :
ultrasonic sound - sound of frequency of more than 20000 Hz which cannot be heard by human ears . but a human child infant can hear upto 25000Hz and animals can be hear more than 20000 Hz . e.g. dogs ( upto 50000 Hz ) , cats , bats ,etc.
The term "ultrasonic sound" refers to sound above the frequencies of audible sound, and nominally includes frequency over 20,000 Hz.
Bats use ultrasound to catch insect in night
ultra sound machine is used to detect fatigue
Infant can hear from 16 Hz to 20000 Hz
Bats use ultrasound to catch insect in night
ultra sound machine is used to detect fatigue
Infant can hear from 16 Hz to 20000 Hz