Signal Processing & DSP

Basic

Decibel (Amplitude Ratio)

Express a voltage/amplitude ratio in decibels.

Formula

L = 20\log_{10}\!\left(\frac{A_2}{A_1}\right)

Variables

LLevel (dB)

A_1Reference amplitude

A_2Measured amplitude

Example

A_2 = 2×A_1: L ≈ 6 dB

Did You Know?

Doubling voltage is +6 dB, but doubling power is only +3 dB — the factor of 20 vs 10 catches many engineers out.

dsp decibel amplitude

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Frequency represented by the k-th bin of an N-point FFT.

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Decibel (Power Ratio)

Express a power ratio in decibels.