What is the name of very high frequency sounds which cannot be heard by the human ear?

Name the characteristic of sound which can distinguish between the 'notes' (musical sounds) played on a flute and a sitar (both the notes having the same pitch and loudness).

Write the full form of dB.

Why do we not hear the screams of a bat ?

Which of the following frequency of sound can be heard by a dog but not by a man?

(a) 50,000 hertz

(b) 15,000 hertz.