Sound WavesHardBloom L3

Question

The intensity of sound 10 m from a tornado siren is a very loud 130 db. At what distance would you need to be for the intensity to drop to 90 db?

Options

A.14.3 m
B.31.8 m
C.210 m
D.400 m

Solution

Sol. β = 130 dB = $10\log\frac{I_{1}}{I_{0}}$

β′ = 90dB = $10\log\frac{I_{2}}{I_{0}}$

⇒ (130 – 90) dB = $10\log\left( \frac{I_{1}}{I_{2}} \right)$

⇒ $\frac{I_{1}}{I_{2}}$ = 104

⇒ $\frac{r_{2}^{2}}{r_{1}^{2}}$ = 104

⇒ $\frac{r_{2}^{2}}{10^{2}}$ = 104

⇒ r2 = 1000 m

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