18/13
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Ratio
18/13
Factorization
2 × 32 × 13-1
Monzo
[1 2 0 0 0 -1⟩
Size in cents
563.3823¢
Names
tridecimal augmented fourth,
low tritone
Color name
3u4, thu 4th
FJS name
[math]\text{A4}_{13}[/math]
Special properties
reduced
Tenney height (log2 nd)
7.87036
Weil height (log2 max(n, d))
8.33985
Wilson height (sopfr(nd))
21
Harmonic entropy
(Shannon, [math]\sqrt{nd}[/math])
~4.23637 bits
[sound info]
open this interval in xen-calc
| Interval information |
low tritone
(Shannon, [math]\sqrt{nd}[/math])
[sound info]
In 13-limit just intonation, 18/13, the tridecimal augmented fourth is a low tritone measuring about 563.4¢. It represents the interval between the 13th and 18th harmonics of the harmonic series.
The low tritone in 17edo approximates 18/13 quite well, while 17edo's approximations of 13/8 and 9/8 are both a little sharp. The inversion of 18/13 is 13/9, a high tritone measuring about 636.6¢; the interval between these two tridecimal (13-based) tritones is 169/162, approximately 73.2¢.