We know that sonic waves across atmosphere are basically areas of high and low pressure. But I couldn't find how much is that pressure. There are online calculators to calculate the sound pressure, but what does let's say a 10 Pascal sound pressure means? That the high pressure area is 5 Pascal above atmospheric pressure and the low pressure area is -5 Pascal below the atmospheric pressure? Or what? Please elaborate.
The maximum change of pressure caused by a sound wave is its pressure amplitude. This would be the difference between high and low pressure areas in the sound wave. When sound is measured in pascals, however, for the purpose of computing decibels by comparing with other sounds, it's just the high pressure against the measuring surface, to the extent that it exceeds ambient atmospheric pressure.