Because the scale is logarithmic, you cannot simply add decibel numbers together.
The is a logarithmic unit used to express the ratio between two values, most commonly sound intensity or electrical power. Unlike linear scales (like inches or pounds), the decibel scale compresses vast ranges of numbers into manageable figures, reflecting how human senses—specifically hearing—actually perceive change. Core Concepts
, the threshold of human hearing. In digital audio, (Full Scale) measures signal level relative to the maximum a system can handle before clipping. Examples of Common Decibel Levels Decibel
: If one sound is significantly louder than another (by 10 dB or more), the quieter sound barely affects the total decibel reading. Measuring Decibels
: Dedicated Sound Level Meters (SPL meters) use calibrated microphones to provide high accuracy for workplace or legal standards. Because the scale is logarithmic, you cannot simply
Understanding dB levels is crucial for hearing safety, as prolonged exposure to sounds over can cause permanent damage. Sound Level Source / Example Perceptual Context 0 dB Threshold of hearing Near silence 30 dB Whisper, quiet library Very quiet 60 dB Normal conversation 85–90 dB Lawnmower, hair dryer Danger Zone : Risk of damage over time 110 dB Chainsaw, rock concert Painful/dangerous after short exposure 140 dB Jet engine, gunshot Immediate hearing damage The "3 dB Rule" and Adding Sound
: Many free apps are available on the Google Play Store or Apple App Store. While convenient for general checks, they may lack the calibration required for official evidence. Core Concepts , the threshold of human hearing
: Named after Alexander Graham Bell, a decibel is literally one-tenth of a "Bel". The Bel itself was found to be too large for common precision.