IDEALregister holes

When we want to know where nodes and antinodes lie within the tube of the instrument, we use the method of the 'ideal register hole'. Such holes can, for different notes, in practice easily establish the position of the nodes.

An ideal register hole is a normal tone hole that is used as a register hole. Unlike the regular very small register holes – which can serve quite a range of notes – such large holes work correctly for only one or two notes, for which notes the hole is (almost) in the correct spot. In this way such holes determine the position of the wave within the tube. When a match is strikingly good, an exclamation mark is added. To establish the acoustical length of the upper register hole we need to remove the pip. Only in this way the hole acts more or less as a normal tone hole.
The table gives written pitch.