🔊 Sound Decibel Calculator

Calculate sound pressure level (SPL dB) drop over distance using the acoustic inverse-square law $L_2 = L_1 - 20\log_{10}(r_2/r_1)$, acoustic pressure in Pascals, and NIOSH/OSHA safe daily exposure limits.

Initial SPL ($L_1$) dB SPL

Source Distance ($r_1$) Meters ($m$)

Listener Distance ($r_2$) Meters ($m$)

SPL at Listener ($L_2$)

90.0 dB SPL

-20.0 dB attenuation

Sound Pressure ($p$)

0.632 Pa

ref: 20 µPa

OSHA Max Safe Exposure

2.5 Hours / Day

NIOSH exchange rate

Perceived Loudness

25% as loud

-10 dB = 1/2 loudness