The International System unit of pressure equal to one Newton (the unit of force required to accelerate 1kg 1m per second per second) per square meter. International standards have established 1 Pascal (Pa) as 94dB SPL. This reference point is now accepted for measuring the sensitivity and signal-to-noise ratio of microphones. A typical signal-to-noise rating might be 70dB, 1 Pa @ 1kHz. So, subtracting 70dB from 94dB (one Pa), you can assume the mic’s self-noise to be 24dB.
The term was named for Blaise Pascal, the 17th-century French philosopher and mathematician. Among his achievements were the invention of an adding machine and the development of the modern theory of probability.
Pascal is also the name of a landmark computer programming language developed in 1970. Generations of computer students learned programming using Pascal, and variants of the language are still widely used today. Much of the original Macintosh operating system was written in Pascal.