What is a decibel (dB)?
The decibel is a logarithmic unit which is used in a number of scientific disciplines. In all cases it is used to compare some quantity with some reference value. Usually the reference value is the smallest likely value of the quantity. Sometimes it can be an approximate average value. In acoustics the decibel is most often used to compare sound pressure, in air, with a reference pressure. References for sound intensity, sound power and sound pressure in water are amongst others which are also commonly in use. Reference sound pressure (in air) = 0.00002 = 2E-5 Pa (rms) ” ” intensity = 0.000000000001 = 1E-12 W/m^2 ” ” power = 0.000000000001 = 1E-12 W ” ” pressure (water) = 0.000001 = 1E-6 Pa Acousticians use the dB scale for the following reasons: 1) Quantities of interest often exhibit such huge ranges of variation that a dB scale is more convenient than a linear scale. For example, sound pressure radiated by a submarine may vary by eight orders of magnitude depending on direction. 2)
helpful in the least is it. Does this make more sense, in one of the contexts that the Decibel is used, it is a measuring unit of sound pressure, or put another way, how much the air pressure in a sound wave varies from the pressure of the still air in the same environment, or it may be the ratio between two or more sources of sound wave pressure.
