Question

Sound Intensity & dB: You are watching the space shuttle rise after it launches. The sound level of the shuttle is 170 dB at a distance of 10.0m from the engine flames. Your seat in the bleachers is 10.00 km away. 25. What is the sound level at your ear (in dB)? Note: Pay attention to the units required for the answer. DIRECT SOUNDS Jettake-off, un shot Jack hann er Threshold of pain Rock concert Dance dub Voice shouting Factory Subway Heavy trafic Busy street 95 20 00

Answer 1

Sound intensity leve is given by

$\beta$=10log10(I/I0)dB .......................(1)

Where I0=10-12 W/m2

When r=10m   $\beta$=170 dB

From (1)

170=10log10(I/10-12)

So I=105 W/m2   

Power,P=I(4$\pi$r2)

When R=10 km=10000 m

Then I=Ir2/R2=105$\times$102/(10000)2=10-1 W/m2

So

Sound level at 10km is

$\beta$=10log10(10-1/10-12)dB =110 dB