From the information, the sound intensity of street traffic is about 10^7 greater than the threshold of hearing.
Therefore; if the threshold of hearing is 1 then the street traffic is 10^7 times greater. Sound intensity is the sound power per unit area (W/m²), a sound energy quantity, the SI units are Watts/square meter. Sound intensity level in decibels is ten times the logarithm of the ratio of the sound intensity to the reference sound intensity of 1 pico watt/m²
Hence; the intensity level is LI = 10 × log (10 ^7)/1) dB
= 70 dB greater than the threshold of hearing at 0 dB
Thus the relative intensity of street traffic is 70 decibels.