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Need to know what equation to use on this problem and what symbol is use for what?
A whistle can be heard up to a distance of 9.8 km. At what distance is the intensity level of the whistle sound equal to 25 dB?
1 Answer
- ?Lv 74 years agoFavorite Answer
You need to know two things:
sound level in dB = 10*log(I / TOH)
where I = intensity, usually in W/m²
and that TOH = threshold of hearing = 1e-12 W/m²
So the output power is such that
1e-12W/m² = P / 4π(9800m)², or
P = 0.0012 W
then
25 dB = 10*log(0.0012W/(4πR²) / 1e-12W/m²)
2.5 = log(0.0012W/(4πR²) / 1e-12W/m²)
10^2.5 = 316 = 0.0012W/(4πR²) / 1e-12W/m²
R = 551 m
Hope this helps!
