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Cent (music)




1200 cents are equal to one Semitone (the interval between two adjacent piano keys) is equal to 100 cents. This means that a cent is precisely equal to 21/1200, the 1200th root of 2, which is approximately 1.0005777895.

If you know the frequencies ''a'' and ''b'' of two notes, the number of cents measuring the interval between them may be calculated by the following formula:

:n = 1200 \log_2 \left( rac{a}{b} ight) \approx 3986 \log_{10} \left( rac{a}{b} ight)

Likewise, if you know a note ''b'' and the number ''n'' of cents in the interval, then the other note ''a'' may be calculated by:

:a = b imes 2 ^ rac{n}{1200}

To compare different tuning systems, convert the various interval sizes into cents. For example, in for this unit is about 6 cents.

A. J. Ellis based the measure on the ''acoustic logarithms'' semitone system developed by de Prony, on Bosanquet's suggestion, and introduced it in his edition of Hermann von Helmholtz's ''On the Sensations of Tone''. It has since become the standard way of measuring intervals in Equal Temperament systems or for comparison with equal temperament systems.


SOUND FILES

The following .ogg files play various cents intervals. In each case the first note played is middle C. The next note a C which is sharper by the assigned cents value. Finally the interval is played.


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