1dB

1 dB is a unit used to express a relative change in level on a logarithmic scale. It is one tenth of a bel, since a bel is defined from a base-10 logarithm of a power ratio. A change of 1 dB corresponds to a power ratio of about 10^(1/10) ≈ 1.2589.

Because power is proportional to the square of amplitude, a 1 dB change in amplitude (with constant impedance) corresponds to a voltage or current ratio of about 10^(1/20) ≈ 1.122, i.e., roughly a 12.2% increase in amplitude. In general, the relationships are dB = 10 log10(P2/P1) for power, and dB = 20 log10(V2/V1) for voltage (with fixed impedance).

The decibel is a relative unit and requires a reference value. Different decibel scales use different references, so 0 dB does not imply absence of signal. Examples include dB SPL (sound pressure level, reference 20 micropascals), dBm (power relative to 1 milliwatt), dBV (voltage relative to 1 volt), and dBFS (digital full scale, relative to the maximum possible digital level).

Uses and interpretation: 1 dB represents a small yet perceptible change in many engineering contexts. It is widely used to specify gains, attenuations, and level differences in audio, telecommunications, and RF systems. Because the scale is logarithmic, equal dB steps denote multiplicative changes in the quantity being measured rather than linear additions.