Formulas For Working With Sound

1 Pascal (Pa)  =  1 Newton/m^2

               =  10 dyne/cm^2

               =  10 microbar

               =  94 dB SPL

Sound Pressure Level (SPL):

dB SPL = 20 * log10(P / P0)

where P is the measured pressure and P0 is a reference pressure in the same system of units:

P0  =  20 microPa  (or microNewton/m^2)

    =  0.0002 microbar (or dyne/cm^2)

This reference pressure corresponds to a sound wave in free air with an intensity (power) I0 = 10^-16 watts/m^2, which is used as the reference for intensity in dB:

Intensity = 10 * log (I / I0)

To convert from SPL to Pa:

Pa = 10^((SPL - 94) / 20)

See also dB, dB From Voltages, Typical dB Applications, Working With dB, RMS "Sum" of dB Values, Absolute dB (SPL, etc.)