How long is....

Discussion in 'Off-Topic Chat' started by TuTuKu, Feb 20, 2005.

  1. TuTuKu

    TuTuKu Active Member

    Does any one know the length of tubing in a cornet, with and without valves pressed?

    Tried to google it but couldn't find a lot...

    Thanks, TuTuKu Xx
  2. yonhee

    yonhee Active Member

    wuldnt it depend on the make?
  3. TuTuKu

    TuTuKu Active Member

    shouldn't do, as the pitch of the note produced depends mainly on the length of tube... which is why a tuba has a heck of a lot more tubing than a soprano cornet!
  4. Roger Thorne

    Roger Thorne Active Member

  5. TuTuKu

    TuTuKu Active Member

    That's great stuff, thanks a lot Roger! Some very useful graphs there!!
  6. yonhee

    yonhee Active Member

    Oh right :oops:
  7. MoominDave

    MoominDave Well-Known Member

    Interesting link, Roger!

    As a rough and ready reckoner, try using the usual wave formula:

    c=f*lambda, where c is the speed of the wave (i.e. the speed of sound), f is the frequency of the second harmonic note (low C down to low F#, depending on which valves you have pressed) in Hertz, and lambda is the length of the instrument.

    c (wave speed) is approximately 340 metres per second (m/s); for a Cornet, low C (pitch) is at a frequency of about 233 Hz (*). Rearrange the formula to get lambda=c/f, and insert these values to get the length of a Cornet open tube to be around about 1.46 metres (~4 feet 9 inches). In fact, it is always going to be a little less than this answer, due to a correction that needs to be made for the bell end.

    (*) To obtain the frequency of a particular note, bear in mind that (at concert pitch) the A above middle C on the Piano is defined to be at 440 Hz. This is the same note as a B in the middle of the treble staff for the Cornet. To find the frequency of a note an octave lower, halve this number; to find the frequency of a note a semitone lower, divide it by 1.05946.

    A similar calculation for a Cornet fingering 1+2+3 gives us a length of 2.06 metres / 6 feet 9 inches. This assumes that the instrument is triggered enough by the player to be in tune. If it is not, you would have to work out the length of each valve slide one at a time, then add them all up.
  8. TuTuKu

    TuTuKu Active Member

    Thanks, the reason i asked the question was to look the theoretical value and compare it with the acutal to see what effect the bell & mpiece had ... just wondered if anyone knew the acutal value!!
  9. Jamie

    Jamie Member

    Er... at the risk of sounding stupid... why?! [​IMG]
  10. Big Twigge

    Big Twigge Active Member

    I didn't read Rogers link....looked a little complex for this time on a sunday evening, but I always remember some music shop guy telling me that a cornet, trumpet and flugel would all hold the same about of water if you filled them up. He was probably lying.
  11. TuTuKu

    TuTuKu Active Member

    A2 physics investigation..... !
  12. brasscrest

    brasscrest Active Member

    Depends on what you mean by "about the same amount". The flugel has more volume, because the bore flares more. So it would hold more water, but how much more would have to be determined via more math than I know or by simple experimentation.
  13. MoominDave

    MoominDave Well-Known Member

    Volume contained by a surface of revolution; model a Flugel as a simple cone from mouthpiece to bell; model a Cornet as half a cylinder, half a cone; away you go... :eek:

    Any bored students out there?
  14. Jamie

    Jamie Member

    I'm a bored student! I don't have any instruments to fill up though! Or, in fact, any idea what you're on about! Surely filling my instrument wont tell me how long my tubes are?!?! Wish my coursework was half as interesting as all this!

    [​IMG] <- ask him!
  15. MoominDave

    MoominDave Well-Known Member

    Okay - I was bored enough during the last half hour at work this afternoon to work this out. I've used the following approximate numbers:

    Length of a Cornet/Trumpet/Flugel: 1.4m
    Mouthpiece radius of each: 0.005m
    Bell radius of each: 0.1m

    The statement I made above about the modelling of the Flugel was in error - of course it should be more or less 1/3 cylindrical, 2/3 conical; in addition to this, the Trumpet is 2/3 cylindrical and 1/3 conical. More or less. If you look at the graphs in Roger's link, you can see that the actual shapes are not so simple, but this is only a rough approximation.

    Using this info, the amount of water that the open tubing on each instrument would hold in litres is roughly:

    Trumpet: 5.3
    Cornet: 7.8
    Flugel: 10.4

    Miss Twigge, you have been deceived!

Share This Page