Decibel (dB) Gain & Sound Pressure Calculator
Calculate audio and electrical decibel gain for voltage (20 log V2/V1), power (10 log P2/P1), sound pressure level (dB SPL), and acoustic volume multipliers.
Calculated Results
Frequently Asked Questions
Why does the decibel scale use both 10 log and 20 log formulas?
Decibels measure the logarithm of power ratios: dB = 10 log(P₂ / P₁). In electrical circuits, power is proportional to voltage squared (P = V² / R). By logarithmic identity, log(V²) = 2 log(V), which turns 10 log((V₂)² / (V₁)²) into the classic voltage formula: dB = 20 log(V₂ / V₁).
How many decibels represent a doubling of perceived loudness?
In psychoacoustics, a +10 dB increase represents an approximate doubling of perceived subjective human loudness. A +3 dB increase represents a doubling of physical acoustic or electrical power (2× power), but sounds only slightly louder to human ears.
What is 0 dB Sound Pressure Level (SPL)?
0 dB SPL is defined as 20 micropascals (20 µPa or 0.00002 Pascals) of sound pressure in air at 1,000 Hz, which is the absolute threshold of normal human hearing.
What decibel sound level causes permanent hearing loss?
Continuous exposure to sound levels above 85 dBA (such as lawnmowers and heavy traffic) causes progressive irreversible hearing damage. Sound levels over 120 dBA (rock concerts, sirens) can cause rapid damage, and 140 dBA (gunshots, jet engines) causes immediate acoustic trauma.