Question

If the warning tag on a lawn mower states that it produces noise at a level of 91.0 dB, what is this in watts per meter squared?

Answer 1

You can use the relationship:
`I(dB)=10log(I/I_0)`
Where `I_0=10^(-12) W/m^2` represents the intensity just audible (correspnding to `0 dB`).
So:
`91=10log(I/10^(-12))`; power `10` both sides and rearrange:
`I=1.25xx10^-3 W/m^2`