Scientific pitch notation (SPN), also known as American standard pitch notation (ASPN) and international pitch notation (IPN), is a method of specifying musical pitch by combining a musical note name (with accidental if needed) and a number identifying the pitch's octave. Although scientific pitch notation was originally designed as a companion to scientific pitch (see below), the two are not synonymous. Scientific pitch is a pitch standard—a system that defines the specific frequencies of particular pitches (see below). Scientific pitch notation concerns only how pitch names are notated, that is, how they are designated in printed and written text, and does not inherently specify actual frequencies. Thus, the use of scientific pitch notation to distinguish octaves does not depend on the pitch standard used. Nomenclature The notation makes use of the traditional tone names (A to G) which are followed by numbers showing which octave they are part of. For standard A440 pitch equal temperament, the system begins at a frequency of 16.35160 Hz, which is assigned the value C0. The octave 0 of the scientific pitch notation is traditionally called the sub-contra octave, and the tone marked C0 in SPN is written as ,,C or C,, or CCC in traditional systems, such as Helmholtz notation. Octave 0 of SPN marks the low end of what humans can actually perceive, with the average person being able to hear frequencies no lower than 20 Hz as pitches. The octave number increases by 1 upon an ascension from B to C. Thus, A0 refers to the first A above C0 and middle C (the one-line octave's C or simply ) is denoted as C4 in SPN. For example, C4 is one note above B3, and A5 is one note above G5. The octave number is tied to the alphabetic character used to describe the pitch, with the division between note letters ‘B’ and ‘C’, thus: "B3" and all of its possible variants (B, B, B, B, B) would properly be designated as being in octave "3". "C4" and all of its possible variants (C, C, C, C, C) would properly be designated as being in octave "4". In equal temperament "C" is same frequency as "B". Use Scientific pitch notation is often used to specify the range of an instrument. It provides an unambiguous means of identifying a note in terms of textual notation rather than frequency, while at the same time