Hint 1.19

log(a)+log(b)=log(ab)
log(a)-log(b)=log(a/b)
log(aⁿ)=n*log(a)
log(1)=0
If a=log₁₀(b), b=10^a
log₁₀(b)=ln(b)/ln(10)

Find expressions for the sound level in dB at the two distances [r₁ = h and r₂ = (x²+h²)^1/2], subtract them, and recall that I₂/I₁ = r₁²/r₂². Be prepared for quite a bit of algebra.

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