Because the scale is logarithmic, you cannot simply add decibel numbers together.
: A decibel always requires a reference point. In acoustics ( dB SPL ), the reference is
: If one sound is significantly louder than another (by 10 dB or more), the quieter sound barely affects the total decibel reading. Measuring Decibels
: 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.
: 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.