Decibels - HyperPhysics ... Decibels Learn what decibel is, how to calculate it, and how to measure sound with a decibel meter. Explore the decibel scale and chart with examples of different sound sources and their dB levels. Definition and examples The decibel (dB) is a logarithmic unit used to measure sound level. It is also widely used in electronics, signals and communication. The dB is a logarithmic way of describing a ratio. The ratio may be power, sound pressure, voltage or intensity or several other things. Later on we relate dB to the phon and to the sone, which measures loudness. But first, to get a taste for logarithmic expressions, let's look at some numbers. (If you have forgotten, go to What is a ... Decibel Metre A decibel metre is a measuring device that measures sound pressure and is used to determine loudness or sound levels. A sound level metre, also known as a sound pressure level (SPL) metre, decibel (dB) metre, noise metre, or noise dosimeter, records sound using a microphone.
