How does flute produce sound

Technically, these actions work because they change the radiation impedance at the embouchure: when a note is 'lipped down', the embouchure hole is "less open" both the hole and angle are smaller so there is more impedance to radiation from the bore to the external field. The effects of the jet itself are more complicated. We have measured these effects explicitly by installing our impedance measuring equipment in a flute head and measuring the impedance at the embouchure hole. This is the impedance of the radiation field, 'looking out' from inside the blowhole, which is partially blocked by the lower lip.

The flutist's lip and face also provide a baffle that reduces the angle for radiation. These results are reported in a recent conference paper - see our research papers site. The interval that can be lipped depends on the details of the impedance spectrum and on some properties of the jet. It is easier to adjust the pitch of notes using a short length of tube, whose impedance spectra have fewer and shallower harmonic minima than do those of long tube fingerings.

The analogous effects are much bigger on the shakuhachi , and are described on that site. The cork and the 'upstream space' Between the point where the embouchure riser meets the main bore of the flute and cork in the closed end of the instrument is a small volume of air.

The cork is normally positioned to be about 17 mm from the centre of the embouchure hole the exact value varies from player to player - see tuning wind instruments. Any very substantial variation seriously upsets the internal tuning of the flute. So how does this work?

This 'upstream air' acts like a spring - when you compress it, the pressure rises. The air in the embouchure riser tube can be considered as a mass. Together they can resonate like a mass bouncing on a spring ie they form a Helmholtz resonator. This has a resonance over a broad range of frequencies, but centred at about 5 kHz.

At much lower frequencies, which is to say over the playing range of the flute, it acts as an impedance in parallel with the main part of the bore, but an impedance whose magnitude decreases with frequency.

The primary effect of this is good: with the cork correctly placed, it compensates for the frequency dependent end effects at the other end of the flute and so keeps the registers in tune with each other. On the other hand, it does reduce the variation in impedance with frequency when the frequency approaches the Helmholtz resonance, and so is one of the effects that limits the upper range of the instrument.

If you push the cork in, as Charanga style players do, you can go further up into the fourth octave, but at the expense of having an instrument whose octaves are badly out of tune. If you want to know more about this effect, download our technical paper about it. To scale the highest reaches of the flute's range, search for 'high playability' fingerings on the virtual flute and the report on F 7 and G7 The important message for flutists, however, is this.

Among the orchestral winds, the flutes have the simplest method of adjusting their internal intonation. If your octaves are narrow, try pushing the cork in a little. If they are wide, pull it out. You will of course have to move the tuning slide as well. See also tuning wind instruments. Cut-off frequencies When we first discussed tone holes , we said that, because a tone hole opens the bore up to the outside air, it shortened the effective length of the tube.

For low frequencies, this is true: the wave is reflected at or near this point because the hole provides a low impedance 'short circuit' to the outside air.

For high frequencies, however, it is more complicated. The air in and near the tone hole has mass. For a sound wave to pass through the tone hole it has to accelerate this mass, and the required acceleration all else equal increases as the square of the frequency: for a high frequency wave there is little time in half a cycle to get it moving.

So high frequency waves are impeded by the air in the tone hole: it doesn't 'look so open' to them as it does to the waves of low frequency. Low frequency waves are reflected at the first open tone hole, higher frequency waves travel further which can allow crossfingering and sufficiently high frequency waves travel down the tube past the open holes.

Thus an array of open tone holes acts as a high pass filter: some thing that lets high frequencies pass but rejects low frequencies. See filter examples. The cut-off frequency for the Boehm flute is a little above 2 kHz. For example, in the acoustic response curve for A4 , you will see that the first four or five resonances become gradually weaker with frequency--this is due to the increasing importance of energy losses due to the 'friction' viscous loss between the air and the wall.

Above 2 kHz, however, the resonances are suddenly much weaker: waves with these frequency propagate down the bore and are radiated gradually from successive tone holes.

The remaining weak standing waves produce resonances with a different frequency spacing, as we shall see in the next section. Before we move on, however, compare the A4 graph with that for B3. The latter is the lowest note on the flute, so there are no open tone holes and therefore no cut-off frequency. Consequently, the resonances fall gradually and uniformly with frequency over the whole range. For the lowest note or two on the flute, there is no array of open holes and so there is no cutoff frequency due to that effect.

In principle, if the higher harmonics were strong enough, one would expect this to lead to a different timbre of these notes. One way to avoid this--a way that is used for the oboe and clarinet--is to supply a bell that radiates high frequencies but not low, and which has a cut-off frequency comparable with that of the tone hole array. The flute has less radiated power at high frequencies than do the oboe and clarinet, so the need for a bell to 'homogenise' the timbre is rather less.

However, a bell would increase high frequency radiation, both for long and short tube notes, and the pinschofon is the name of such an instrument. This technical paper gives measurements and analyses of cutoff frequencies and crossfingering in baroque, classical and modern flutes.

There is also a more detailed explanation of cut-off frequencies and their effects here. Frequency response of the flute So now let's look at the acoustic impedance spectrum of the modern flute. We'll choose the fingering used for C 5 and C 6, with nearly all tone holes open. It is shown in the graph below. This graph covers a wide frequency range, but does not show much fine detail.

For more detail, see C 5. Below about 2. The first three minima all support standing waves, and you can therefore play the notes C 5, C 6 and G 6 with this fingering.

However, above 2. This is because of the high pass filter mentioned above under cut off frequencies. Higher still, around 5 kHz, the resonances almost disappear completely, because they are shorted out by the Helmholtz resonator discussed above under the cork and the 'upstream space'.

Above this frequency range, the Helmholtz resonator is no longer a short circuit, so the resonances reappear, although they are weak because of the 'friction' of the air with the walls increased effect of viscothermal losses at high frequencies.

Notice, however, an important difference. The spacing of peaks or troughs in the graph at the low frequency end is about Hz roughly the frequency of C 5, and corresponding to a standing wave in the half of the flute with no tone holes. At high frequencies, the spacing of peaks or troughs is about Hz.

This is the frequency of C4, and corresponds to the standing wave over the whole length of the flute. At these high frequencies, the wave in the bore of the flute propagates straight past the open tone holes, not 'noticing' that they are there, because of the inertia of the air discussed above under cut off frequencies. This is something like creating many different recipes from a given set of ingredients, by varying selection and amounts.

The flute sound has fewer types of harmonic vibration than almost any other instrument, and this is the main factor in the production of its distinctive tone. This is done through lip and breath adjustment. The fundamental, left without support, drops out, leaving the first harmonic as the lowest note, and causing the second octave to be heard.

This is why the second octave can be produced using the same fingerings as the first. If the travel time of the air stream is cut down still further, the air stream fluctuations will hook into the third and then the fourth harmonics, dropping the previous, slower harmonic at each step.

Both the third and the fourth harmonics are used in the production of the third octave. To make the notes of the third octave easier to play, venting is also used. Venting also improves the tuning on some notes. This is only a brief, partial account of what is known about the complexities of sound production in the flute. Search New Contact. This placement of the embouchure hole at a distance of 17mm from the end of the pipe, and the conical shape of the head joint are the solution for providing this pitch interval correction.

This distance and shape is based on the measurements arrived at through a long process of trial and error undertaken by the German instrument maker Theobald Boehm in the 19th century. Not all flutes have a split E mechanism, but on those that do, it is easier to produce an E in the third top octave. When playing this top E, a player releases their left ring finger. If you look at the air oscillation waveform when this happens, you can see that an antinode where the oscillation is greatest is located at the left ring finger key.

For action without a split E mechanism, when the left ring finger is released, the key next to it from the player's perspective, just to the right of the ring finger opens along with it. Because of this, it is harder to fix the antinode of the wave, making it harder to produce the top E.

Instruments that feature a split E mechanism avoid this situation using this construction that automatically closes the key immediately to the right of the left ring finger when fingering an E. This makes it easier to fix the antinode of the wave, and therefore easier to produce the top E. Musical Instrument Guide. The Structure of the Flute How is the sound produced? The flute produces a sound as follows: First, it is the head joint that produces the sound.

Why does it make a sound? What happens inside the head joint? Interior of head joint. The head joint is not perfectly cylindrical in shape The head joint tube narrows toward its left end.

It is primarily the keywork that is used for sound production, whereas the technique of overblowing , so important on brass instruments, plays only a subordinate role on the flute. This means that flutists mainly use naturals 1 and 2 and only rarely naturals 3 and 4. With the aid of the keys the notes from B3—D5 are played starting from the fundamental 1st natural. The footjoint is detachable; the C footjoint is standard and contains the tone holes for the low notes from Eb4 to C4.

By replacing it with a B footjoint B3 becomes playable as well although the higher notes do not respond so well on this footjoint.