## College Physics (4th Edition)

When all eight cars are running, the intensity level is $107~dB$
We can find the intensity of one car: $\beta = 10~log\frac{I}{I_0}$ $98.0 = 10~log\frac{I}{I_0}$ $9.80 = log\frac{I}{I_0}$ $10^{9.80} = \frac{I}{I_0}$ $I = (10^{9.80})~I_0$ $I = (10^{9.80})~(1.0\times 10^{-12}~W/m^2)$ $I = 6.31\times 10^{-3}~W/m^2$ We can find the total intensity from all eight cars: $I = 8\times (6.31\times 10^{-3}~W/m^2)$ $I = 5.05\times 10^{-2}~W/m^2$ We can find the intensity level with all eight cars running: $\beta = 10~log\frac{I}{I_0}$ $\beta = 10~log\frac{5.05\times 10^{-2}~W/m^2}{1.0\times 10^{-12}~W/m^2}$ $\beta = 107~dB$ When all eight cars are running, the intensity level is $107~dB$.