Scientific pitch notation (or SPN, also known as American Standard Pitch Notation (ASPN) and International Pitch Notation (IPN)) is a method of specifying frequency by combining a musical note name (with accidental if needed) and a number identifying the pitch's octave.  Scientific pitch was first proposed in 1713 by French physicist Joseph Sauveur and was defined so that all C's are integer powers of 2, with middle C (C4) at 256 Hertz. With changes in concert pitch and the widespread adoption of A 440 as a musical standard, new scientific frequency tables were published by the Acoustical Society of America in 1939, and adopted by the International Organization for Standardization in 1955; C₀ is now 16.352 Hz instead of 16.