// conversions › 2 · Mechanics & Fluids
Convert acoustic and signal levels between decibels, bels, nepers, sound pressure (Pa) and sones on a logarithmic scale.
dB = 20·log10(p/p_ref); p_ref = 20 µPa. 1 Bel = 10 dB; 1 Np = 20/ln10 dB.
It moves between logarithmic loudness and signal units — decibels, bels, nepers — and physical sound pressure in pascals, plus perceived loudness in sones. Everything is anchored on the decibel using the standard 20 µPa reference pressure.
Human hearing spans a vast range of pressures, so we measure sound on a log scale: every +20 dB is a tenfold increase in pressure. That is why 0 dB is not silence but the threshold of hearing.
0.2 Pa to dB SPL: 20 × log10(0.2 / 20e-6) = 20 × log10(10000) = 80 dB SPL.
The logarithmic slider marks reference points — whisper (~30 dB), conversation (~60 dB), city traffic (~85 dB) and jet engine (~140 dB) — so your value lands in a recognisable everyday context.
Sound pressure and sone inputs must be positive (a log of zero or a negative is undefined). The sone↔dB mapping is an approximation at 1 kHz and is not a substitute for a calibrated loudness measurement.