db måler

"Decibel with the abbreviation dB is equal to one-tenth of a bel, after Alexander Graham Bell.
It is a measuring system first used in telephony in 1929.
It is a logarithmic unit of measurement that expresses the magnitude of a physical quantity, usually power or intensity, relative to a specified or implied reference level. Since it expresses a ratio of two quantities with the same unit, it is a dimensionless unit.
The inventor of the SPL meter (sound pressure level meter) was not Alexander Graham Bell, but it were the engineers of Bell Telephone Company, New Jersey"