15/11

Interval information

Ratio	15/11
Factorization	3 × 5 × 11-1
Monzo	[0 1 1 0 -1⟩
Size in cents	536.9508¢
Names	undecimal augmented fourth, undecimal grave infra-augmented fourth
Color name	1uy4, luyo 4th
FJS name	[math]\displaystyle{ \text{A4}^{5}_{11} }[/math]
Special properties	reduced
Tenney height (log2 nd)	7.36632
Weil height (log2 max(n, d))	7.81378
Wilson height (sopfr(nd))	19
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The interval 15/11, known most frequently as undecimal augmented fourth, is the difference between the 11th and 15th partials of the harmonic series. It is 536.95 cents wide, exactly 45/44 larger than a perfect fourth, and almost exactly a sixth-tone sharper than a 12edo fourth. It is narrower than 11/8 by exactly 121/120, and is wider than 27/20 by exactly 100/99. Additionally, it is narrower than 243/176 by exactly 81/80, which lends to it being called the undecimal grave infra-augmented fourth. 15/11 can be called a superfourth, as it falls between the interval categories of perfect fourth and tritone. 4 steps of 9edo is an excellent approximation for 15/11.

See also

• 22/15 – its octave complement
• 11/10 – its fifth complement
• Gallery of just intervals