Ignition noise of foreign and domestic vehicles in use in the United States

Electromagnetic noise from the ignition systems of more than 11,000 individual vehicles in service in the United States in mid-1977 was measured at 50 and 153 MHz. We found very little difference between the noise of U.S. domestic and foreign vehicles. Older vehicle groups are noisier than newer vehicles groups--a fact which may be accounted for by either of two causes: a) some vehicles in a group become noisier with age, b) newer vehicles may have improved noise suppression systems. Measurements made in a single year will not show which effect predominates. We found the greatest noise differences between vehicle types (cars, trucks, and so on).