### Properties of DB Scales

In every kind of dB, a factor of 10 in amplitude increase corresponds to a 20 dB boost (increase by 20 dB):

and , of course. A function which is proportional to is said to fall off'' (or roll off'') at the rate of dB per decade. That is, for every factor of in (every decade''), the amplitude drops dB.

Similarly, a factor of 2 in amplitude gain corresponds to a 6 dB boost:

and

dB

A function which is proportional to is said to fall off dB per octave. That is, for every factor of in (every octave''), the amplitude drops close to dB. Thus, 6 dB per octave is the same thing as 20 dB per decade.

A doubling of power corresponds to a 3 dB boost:

and

dB

Finally, note that the choice of reference merely determines a vertical offset in the dB scale:

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