Which of the following statement is or are correct about longitudinal mechanical waves?

[A] The longitudinal mechanical waves which lie in the frequency range 20 Hz to 20000 Hz are called audible or sound waves

[B] The longitudinal mechanical waves having frequencies less than 20 Hz are called infrasonic

[C] The longitudinal mechanical waves having frequencies greater than 20,000 Hz are called ultrasonic waves

[D] All of the above are correct