Decibel levels

QUESTION: The decibel level of a jackhammer is 130 dB relative to the threshold of hearing.
[1x10^-12 Wm^-2 ].
Determine the decibel level if TWO jackhammers operate side by side.

Answer:

The defining equation for decibel levels is:

dB = 10 log(Intensity 1/Intensity at threshold)

For one jack hammer this is 130 dB and so solving this

130 = 10 x log(Intensity 1/1x10^-12) 13 = log(Intensity 1/1x10^-12)

Intensity for one jackhammer (Intensity 1) = 10 Wm^{- 2}.

For two jackhammers the intensity would be 20 Wm^{- 2}.

Therefore dB level = 10 x log(2x10/1x10^-12) = 10 x log(2x10¹³) = 133 dB.