Question About Key Placement (Physics of Flutes)

MJ1619 · Post by **MJ1619** » Sun Aug 31, 2008 8:46 pm

Hey everybody,

I've got what is probably a very dumb question, but I am going to ask it anyway because it is bugging me. I'm interested in getting a keyed flute, and in my search I keep seeing that the Eb key is on the foot-joint, while the F# key seems to be located between the toneholes for D and E.

My question is, why is this the case? I know (for a fact), that Eb is enharmonic to D# and therefore is higher in pitch than D. Why, then is the tone hole (with key) for this note, below the D tonehole? I was under the impression that the pitch of the note is determined by the vibrating column of air in the instrument and, therefore, a longer column of air would yield a lower pitch. What effect does the tone hole size have on the pitch? Also, what type of oscillator is a flute (i.e. a panpipe or Romanian Nai operates on a Helmholtz oscillator)?

Thank you for your help and patience as I try to understand.

Michael

talasiga · Post by **talasiga** » Sun Aug 31, 2008 9:16 pm

If XXX XXX fingering gives you a D then the the D vent (air outlet) is lower than XXX XXX. Follow? The D vent is actually at the end of the tube, you know the opening at the bottom of the flute, or if the flute has extra holes below thwe XXX XXX as in XXX XXX O O, the D vent is the first of those extra holes.

Just to complete this explanation
if XXX XXX O vents the D
and
XXX XXO vents the E
then somewhere between the 2 is the vent for D#/Eb
Lets say its this little hole here (see red):-
XXX XXXo O.

jemtheflute · Post by **jemtheflute** » Sun Aug 31, 2008 9:55 pm

Nicely done, talasiga!

Just to add, Michael, that your "mistake" is a common one at which you shouldn't be abashed. It takes a bit of a mental jump to separate the player's association of the fingering (name for what you get when you cover a hole) from the note that sounds when you open the hole under that finger........ Cover the E tone-hole (no.6) with the 6th finger (of the main sequence on a keyless flute) and you get D (if you're not holding an Eb key open!), provided by the next open hole as talasiga explained so well. The fingering gives a D, but the tone-hole when open sounds E. Examine a fully keyed flute carefully and name the HOLES (however covered, whether keyed or not, standing open or standing closed) sequentially by semitone from the open C end upwards and you'll get the sense of it - and gain a better understanding of what you actually do in playing it.

I'm afraid I don't know about your second question.

MJ1619 · Post by **MJ1619** » Sun Aug 31, 2008 10:51 pm

talasiga and jem,

Thank you for your replies. I realize now where my misunderstanding came from. I have never seen the foot-joint of a simple-system flute up-close and was basing my question on the few pictures I had seen. Looking at those photos, I saw that the C and C# keys operated via double-lever system, such that when depressed they actually closed the toneholes (thereby increasing the length of resonating column of air = lower pitch) rather than opened them. For some reason, I thought that the Eb key operated via the same principle and didn't realize that it was just one lever and opened the tonehole (thereby decreasing the resonating length of the column of air = raised pitch), rather than closed it. The D vent hole for a C foot-joint flute is actually the C# tonehole, when the Eb key isn't depressed.

Thank you again for taking the time to help with this. Don't worry about the second question. I probably can figure that one out too if I just think about it a little longer - like I should have done before I posted the first one.

Michael

Denny · Post by **Denny** » Sun Aug 31, 2008 11:02 pm

some light reading
Flute Acoustics

Terry McGee · Post by **Terry McGee** » Mon Sep 01, 2008 12:21 am

On the second question, it's probably fair to call it a transmission line resonator (I'm not sure what the acousticians would call it, but can ask if you really want to know!). The wavefront caused by the jet entering the embouchure hole travels down the tube, reflects at the first open hole, zooms back up the tube and deflects the jet back out of the hole. Then it all starts over again. So the period between wavefronts is proportional to the length of the tube. And the frequency, and therefore the pitch, are proportional to the inverse of the period. Longer tube, longer period between cycles, therefore lower frequency of cycles, therefore lower pitch.

In the Helmholtz oscillator, the timing element is a cavity, eg a bottle. The bigger the bottle, the longer it takes to fill, etc. So its the capacity of the cavity, rather than the length of the tube that determines pitch. The ocarina is the well known example.

The cavity between the stopper and the embouchure hole is a Helmholtz resonator, but its frequency of resonance is set above the range of the flute. The lower skirt of its resonance is used to counter the rising impedance (due to inductance) of the embouchure hole which would otherwise flatten the third octave.

The size of the fingerholes is important because the embouchure and fingerhole chimneys are essentially in series with the main tube, thus making it longer than it appears. Considerably longer, as the chimneys are smaller diameter. Making them bigger makes them look shorter, thus sharpening the flute.

Terry

jemtheflute · Post by **jemtheflute** » Mon Sep 01, 2008 4:37 am

Thanks, Terry! Best explanation of that I've seen.

Good thread, this. Therefore, thanks Michael too.