Comparing noise sources and effects Boston Globe
Decibels, named for Alexander Graham Bell, measure the intensity of sound waves. A 10-point increase in decibels corresponds to a tenfold increase in power — a 30-decibel noise is 10 times more powerful than a 20-decibel noise and 100 times more powerful than a 10-decibel noise.

* Permissible exposure time for continuous noise before possible hearing damage can occur, according to the National Institute for Occupational Safety and Health and CDC. If a sound reaches 85 db or stronger, it can cause permanent hearing damage.
SOURCES: Temple University Department of Civil/Environmental Engineering (www.temple.edu/departments/CETP/environ10.html); www.soundinstitute.com; www.dangerousdecibels.org/hearingloss.cfm
Globe Staff Graphic / Joan McLaughlin