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This is a list of the fundamental frequencies in hertz (cycles per second) of the keys of a modern 88-key standard or 108-key extended piano in twelve-tone equal temperament, with the 49th key, the fifth A (called A 4), tuned to 440 Hz (referred to as A440). [1] [2] Every octave is made of twelve steps called semitones.
Notes in it include a prime symbol below the note's letter. Names of subsequent lower octaves are preceded with "sub". Notes in each include an additional prime symbol below the note's letter. The octave starting at tenor C is called the "small" octave. Notes in it are written as lower case letters, so tenor C itself is written c in Helmholtz ...
An 88-key piano, with the octaves numbered and middle C (cyan) and A 4 (yellow) highlighted A440 is widely used as concert pitch in the United Kingdom [ 8 ] and the United States . [ 9 ] In continental Europe the frequency of A 4 commonly varies between 440 Hz and 444 Hz. [ 8 ]
For instance, 660 Hz / 440 Hz (a ratio of 3:2) constitutes a fifth, and 880 Hz / 440 Hz (2:1) an octave. Such intervals (termed "just") have a stability, or purity to their sound, when played simultaneously (assuming they are played using timbres with harmonic partials) because pure intervals do not waver or beat regularly.
Likewise, if a string tuned to 220 Hz (with a harmonic at 440 Hz) is played together with a string tuned at 442 Hz, the same 2 Hz beat is heard. [4] Because pianos typically have multiple strings for each piano key, these strings must be tuned to the same frequency to eliminate beats.
In musical notation, the different vertical positions of notes indicate different pitches. Play top: Play bottom: Pitch is a perceptual property that allows sounds to be ordered on a frequency-related scale, [1] or more commonly, pitch is the quality that makes it possible to judge sounds as "higher" and "lower" in the sense associated with musical melodies. [2]
Sound is a traveling longitudinal wave, which is an oscillation of pressure. Humans perceive the frequency of a sound as its pitch. Each musical note corresponds to a particular frequency. An infant's ear is able to perceive frequencies ranging from 20 Hz to 20 000 Hz; the average adult human can hear sounds between 20 Hz and 16 000 Hz. [11]
Diagram of beat frequency. In acoustics, a beat is an interference pattern between two sounds of slightly different frequencies, perceived as a periodic variation in volume whose rate is the difference of the two frequencies. With tuning instruments that can produce sustained tones, beats can be readily recognized.