For a quick lesson on how to use the NIOSH (National Institute of Occupational Safety and Health) app to measure decibels and noise, check out my latest Soundproofist video. This handy app is free, although only available for iOS devices right now. It's a great app to use if you want to measure average and maximum noise levels with either A-weighted or C-weighted decibels. You can save each measurement as a report. Learn more about measuring noise and about soundproofing from Soundproofist . Download the free NIOSH app from the App Store and learn more about it from this CDC documentation .