4. Last audible sound for most of the human ear is :

(A) 10.0 μbar
(B) 0.0002 μbar
(C) 0.005 μbar
(D) 5.0 μbar

Ans. (B) 0.0002 μbar

Threshold of hearing :
20 Millipascals (20 μPa) Or 0.0002 millibars (0.0002 μbar) is the threshold of hearing: the smallest perceptible sound. It is the level at which someone with perfect hearing can first detect a 1kHz tone.


The ear can hear sounds ranging from 20Hz to 20kHz. It is most sensitive to frequencies between 500Hz and 4000Hz, which corresponds almost exactly to the speech band.