A decibel (dB) is 1/10th of a bel (B), so 10 decibel = 1 bel. A decibel value by itself does not mean anything. It expresses a ratio, typically of power or intensity, on a logarithmic scale.

In electronics, voltage and current amplification are calculated as 20 * log_{10} and power as 10 * log_{10}. Logarithms are the inverse of exponentiation. For instance, the logarithm to the base 10 of a number is the power to which 10 must be raised to produce that number.

For example, since 10^{2} = 100, the logarithm base 10 of 100 is 2, or log_{10} (100) = 2.

To calculate the amplification of voltage by a **factor of 100**, we apply this formula: 20 * log_{10} (100) = 20 * 2 = **40 dB**.

And a **factor of 10** is calculated as 20 * log_{10} (10), which is **20 dB**.

**Double the factor** is 20 * log_{10}(2). You need to look up (or use a calculator), what the value of x is for this equation. 10^{x} = 2. It's approximately 0.301. Because 20 * 0.301 is close to 6, in electronics **6dB** is considered as **doubling the factor**.