HAND-BOOK OF ACOUSTICS.
Summary. To find approximately the vibration number of any given flue-pipe; divide the velocity of sound by twice the length of the pipe for open, and by four times its length for stopped pipes.
The pitch of an open pipe is not exactly the same as that of a stopped pipe of half its length.
The pitch of a flue pipe is sharpened by a rise of temperature.
Wooden pipes sharpen more than metal ones for the same increase of temperature.
Nodes are produced in flue pipes by the meeting of two rarefactions or of two condensations travelling in opposite directions: consequently it is at the nodes that the greatest variations in density occur.
The open end of a pipe is always an antinode. „ closed ,, ,, ,, ,, anode.
When the air column in an open pipe vibrates with one node only, that is as a whole, the fundamental (say d|) is produced; when with two nodes only, that is in two halves, the 1st Harmonic (d); when with three nodes only, the 2nd Harmonic (s); and so on.
When the air column in a stopped pipe vibrates with one node only, that is as a whole, it gives the fundamental (say d|); when with two nodes, that is in three thirds, its 1st Harmonic (s); when with three nodes, its 2nd Harmonic (n1); and so on.
The tones produced by flue pipes are compound, because of the fact, that the air column vibrates simultaneously, as a whole and in aliquot parts, each part producing an overtone of a pitch corresponding to its length.
Stopped pipes only give the partials of the odd series, 1, 3, 5, &c.
The flute is a flue pipe of variable length.
The pitch of a reed is lowered by a rise of temperature.
The sounds produced by reeds are rich in overtones.
The fundamental tone of a reed-clang may be strengthened relatively to its overtones, by placing over the reed, a pipe which is in unison with that fundamental.
The Clarinet, Oboe, and Bassoon are stopped pipes, in which the pipe governs the reed, that is to say, the tones produced depend on the varying length of the pipe, and not upon the reed. The