The decibel scale is a logarithmic scale for measuring the sound intensity level. Because the decibel scale is logarithmic, it changes by an additive constant when the intensity as measured in W/m2 changes by a multiplicative factor. The number of decibels increases by 10 for a factor of 10 increase in intensity. The general formula for the sound intensity level, in decibels, corresponding to intensity I is
β=10log(II0)dB,
where I0 is a reference intensity. For sound waves, I0 is taken to be 10−12W/m2. Note that log refers to the logarithm to the base 10.
Part A) What is the sound intensity level β, in decibels, of a sound wave whose intensity is 10 times the reference intensity (i. e., I=10I0)?
Part B) What is the sound intensity level β, in decibels, of a sound wave whose intensity is 100 times the reference intensity (i. e. I=100I0)?
Express the sound intensity numerically to the nearest integer.
β = dB
One often needs to compute the change in decibels corresponding to a change in the physical intensity measured in units of power per unit area. Take m to be the factor of increase of the physical intensity (i. e., I=mI0).
Part C) Calculate the change in decibels ( Δβ2, Δβ4, and Δβ8) corresponding to m=2, m=4, and m=8.
Give your answers, separated by commas, to the nearest integer--this will give an accuracy of 20%, which is good enough for sound.