Science 2026-05-04 3 min read By Konvertibly Team

Decibel Calculator: Sound Level, dB Conversions, and Hearing Safety

Calculate sound levels in decibels (dB), convert between power and intensity ratios, combine multiple sound sources, and understand safe noise exposure limits.

The Decibel Scale

The decibel is a logarithmic unit expressing the ratio of two values (sound pressure, power, voltage). A 3 dB increase doubles acoustic power; a 10 dB increase is perceived as roughly twice as loud.

Formulas

Sound Level: L = 10 × log₁₀(I/I₀)  (dB)
I₀ = 10⁻¹² W/m² (threshold of hearing)

Power ratio:   dB = 10 × log₁₀(P₂/P₁)
Voltage ratio: dB = 20 × log₁₀(V₂/V₁)

Combining sources (incoherent):
L_total = 10 × log₁₀(10^(L1/10) + 10^(L2/10))

Common Sound Levels (dB SPL)

0 dB: threshold of hearing
30 dB: quiet library
60 dB: normal conversation
85 dB: heavy traffic (damage threshold with prolonged exposure)
110 dB: concert front row
140 dB: jet engine at 30m (pain threshold)

Hearing Safety (NIOSH)

85 dB: 8 hours maximum
88 dB: 4 hours (every +3dB halves safe exposure time)
91 dB: 2 hours
94 dB: 1 hour
100 dB: 15 minutes

Convert decibels: Free Decibel Calculator