Well a lawn mower (especially one that's nearby) can be as loud as a motorcycle - 95 decibels. Here's a great article on how noise pollution can increase your risk of heart attack. For every 10 decibels of noise in the neighborhood (traffic, screaming motorcycles, lawnmowers), the risk of heart attack goes up 12 percent. Perhaps it's time to purchase some ear plugs if you live in a high traffic noise area.
You can read more about it here: