What the numbers mean
A short step on the scale represents a large multiplier.
The decibel scale is logarithmic: equal steps represent equal ratios. An increase from 60 to 70 dB means ten times the sound intensity. Another ten-decibel step multiplies it by ten again, making 80 dB one hundred times the intensity at 60 dB.
Read the sourcesA scale built for very different sizes
Sound intensities can span an enormous range. A logarithmic scale compresses that range into manageable numbers. For an intensity ratio, the difference is 10 times its base-ten logarithm. Working backwards, divide the decibel difference by ten and use that as a power of ten. A 10 dB difference gives 10 to the power of one. [2]
Intensity is not the same as loudness
The University of New South Wales distinguishes the physical measurement from what a listener hears. Perceived loudness also depends on the sound's frequency and the listener. Ten times the intensity does not mean ten times the perceived loudness. A phone's volume percentage is another scale again; it cannot be read directly as decibels. [1]
Always check what the decibels compare
Decibels express a ratio relative to a reference. They are used for power, intensity and other quantities, with different formulas for some measurements such as pressure amplitude. NIST emphasises specifying the reference. Here both readings describe sound intensity against the same reference, so their difference can be converted into one intensity ratio. [2]