# physics

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Residents of Hawaii are warned of the approach of a tsunami by sirens mounted on the tops of towers. Suppose a siren produces a sound that has an intensity level of 120 dB at a distance of 2.0 m. How far away can the siren be heard?

• physics -

r =2 m.
B = 120 dB = 10•log(I2/I1)
I2 =I1•10^12.
The siren can be heard until B = 0 or
10•logx = -120.
x=10^-12,
(2/r)² =10^-12
2/r = 10^-6,
r=2•10^-6 m.

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