At 13 inches the data was missing, which is why the graph appears to drop off. The register hole is at 4.75 inches, while the first tone hole is at 6.25 and the second at 7.5. At 4.75 all of the harmonics have a slight dip, while at 7.5 all of the harmonics are antinodes. The tone hole at 6.25 inches doesn't appear to have any trend within any subset of the harmonics. Here, the even harmonics are as bumpy as the odd and all but the first harmonics star on an antinode.