I really like this graphic for that effect: http://www.leiserstrassenverkehr.bayern.de/assets/stmi/vum/strasse/fittosize__620_240_53282c6c94df294eeee545ab11a553

I really like this graphic for that effect: http://www.leiserstrassenverkehr.bayern.de/assets/stmi/vum/strasse/fittosize__620_240_53282c6c94df294eeee545ab11a5532c_leiserverkehr_entstehung.jpg http://www.leiserstrassenverkehr.bayern.de/assets/stmi/vum/s... Yellow is trucks, blue is cars. Full line is total noise, broken line is noise by wind and tires, dotted is noise by the motor.