Question

define the following :- 1) infrasonic sound waves
2) ultrasonic sound waves

Answer 1

Waves which frequency less than 20hz called infrasonic sound
These waves come in earthquake and listen by other animals
Ultrasonic sound which frequency more than20000 hz
ex bat

Answer 2

 Infrasonic sound waves :- Sound waves with frequencies less than 20 Hz                                                 are known as infrasonic waves. Such waves are                                              produced by large vibrating bodies. The                                                          earthquake, volcano eruptions, big animals like                                             whales and elephants produce infrasonic waves.                                          
We can't listen these waves.                

Ultrasonic sound waves :- Sound waves with frequencies more than                                                        20,000 Hz are known as ultrasonic waves or                                                   ultrasound. Bats and some insects can produce                                              and also listen these waves. We can't hear these                                            waves.