PHILIPPE BOLTON, RECORDER MAKER
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 Version française Home page Recorders page |
THE RECORDER AIR COLUMN: low d
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The following chart shows how the recorder's first register works. Antinodes (A) are low pressure zones with high velocity or movement. Nodes (N), on the contrary are high pressure zones with no velocity or movement. Basically recorder air columns have an antinode at each end and a node in the middle. The 2 graphs show the pressure and velocity variations within the instrument's bore. When a wave goes down the instrument from the windway end, a corresponding wave goes up the instrument from the other end. These meet at the node and bounce back in the opposite direction. When they reach their respective ends they bounce back once more, and this continues as long as the player keeps blowing. The chart shows the position of the nodes and antinodes. There is one graph for velocity and one for pressure variations along the air column. The arrows show the direction of the vibrations. The recorder's bore profile, and the open (o) and closed (x) holes are shown underneath. Opening a hole could amount to cutting the air column at that point, but on recorders the holes are not big enough, so the air pressure and velocity diminish gradually further down. |
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 = closed hole
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| This chart is for a baroque alto or treble recorder. |
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Philippe BOLTON, |
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