# Math

posted by
**Donna**
.

Formula given:

The decibel (dB) scale for measuring loudness, d, is given by the formula

d = 10 log base ten(I X 12 to the power of 12) where I is the intensity of sound in watts per square metre.

a) Find the number of decibels of sound produced by a jet engine at a distance of 50 metres if the intensity is 10 watts per square metre.

b) Find the intensity of sound if the sound level of a pneumatic drill 10 metres away is 90 decibels.

c) Find how the value of d changes if the intensity is doubled. Give your answer to the nearest decibel.

d) Find how the value of d changes if the intensity is 10 times as great.

e) By what factor does the intensity of sound have to be multiplied in order to add 20 decibels to the sound level?