The unit of force in the cgs (centimeter grams second) system of units. A force of 1 dyne acting on a mass of 1g imparts an acceleration of 1cms-2.
1 dyne = 10-5 newton
The old standard reference level for sound pressure was 0.0002 dyne/cm2. The same level today is expressed as 20 micro pascals, or 20 µPa.