## Understanding and calculating decibels

Decibel is a special unit that is a little different from other measuring units in everyday practices. This is non physical unit but more mathematical understanding. Decibel (dB) units are similar to percent (%), just different calculation and purpose. As a percent units so decibels are used to compare two quantities. As whole value in percents is expressed as 100% so decibels is more complex and it is a ratio of two independent quantities. Decibels mostly are used for energetic parameters like power or voltage and current. Decibel (dB), equal to 0.1 bel (B) . Bel â€“ is a decimal logarithm of ratio of two powers. If these powers P1 and P2, then expression looks like: NP=lg(P2/P1) [B] In physical nature any power can be compared: electrical, acoustic, mechanical. Important part is that both variables were expressed in same units â€“ watts, mili-watts, horse powers (HP). Practically speaking Bel (B) is way to big unit. Even big ratios of power gives a small B. For instance P2/P1=100, lg100=2. If P2/P1=1000, lg100=3. So the big difference 100 and 1000 in bels will be 2B and 3B. For more detailed and convenient use bels are converted in decibels like 2B->20dB: DP=10lg(P2/P1) As…