Question

what are audible and in-audible sounds

Answer 1

It is the property of sound that most determines pitch. The generally accepted standard range of audible frequencies is 20 to 20,000 Hz, although the range of frequencies individuals hear is greatly influenced by environmental factors.

Answer 2

Audible sound means sounds which can be heard and in-audible means sounds which cannot be heard
The audible range of humans is from 20 hertz to 20000hertz