All about the Decibel (dB)

Having read a good many letters and emails from various correspondents we concluded that although the decibel (dB) is one of the most frequently used units in audio, RF electronics and acoustics, it is unfortunately one of the least understood. High time, we thought, to clear up the misunderstandings and publish Mr. Basquin’s article on the subject.Basically, the dB is a relative unit, expressing the ratio of two values using the same unit:–the value being measured–a clearly defined and indicated reference value.A logarithmic scale is used to make it easier to handle otherwise unwieldy numbers. For example, the ratio of 0.0000316 V to 1 V is expressed as: –90 dB.