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 * log(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)