18/13
(Redirected from 18 13)
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| Ratio | 18/13 |
| Factorization | 2 × 32 × 13-1 |
| Monzo | [1 2 0 0 0 -1⟩ |
| Size in cents | 563.38234¢ |
| 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{n\cdot d}[/math]) |
~4.56808 bits |
[sound info] | |
| open this interval in xen-calc | |
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¢.