Question

A new airport is being built 650 meters away from a school. The noise level 50 meters away from planes that will land at the airport is 140 dB. In open space between the airport and the school, noise level decreases by 15 dB each time the distance increases tenfold. How far away would the school have to be moved to make the sound manageable? Give at least 2 options to reconcile the issue without moving the school or airport? (don't use log)

Answer 1

We know that the distance between the school and the airport = 650 m
The sound intensity in dB at airport is = 140 dB
Rate of decreasing the sound level when distance increases 10 times(tenfold) = 15 dB
Manageable hearing limit for human = 60 dB
Therefore the sound level should be decrease by = 140 - 60 = 80 dB
Therefore ,
= 80/15 = 5.33
We have to increase the distance = 5.33*10*(650) = 34.645 km
Hence the distance must be increased by 34.645 km
If we do not want to move the school then we should use
(1) absorptive material in the building like cell foam or mineral wool.
(2) We can use sound demodulator at our building.