If a sound note has intensity (I), equals to faintest audible sound (I₀), then will be it's sound level?

20 dB

10 dB

0 dB

None of these

The sound level β (in dB) is given by:

β = 10 log(I / I₀)

where I₀ is the threshold intensity (faintest audible sound). Given I = I₀:

β = 10 log(1) = 0 dB