Acoustics of the flute from a different perspective

Zoltán Lakat

Parlando Journal of Research in Music Education, Vol. 4, 2017

  • Why are lower notes much harder to play?
  • Why are the notes of the third octave higher?
  • Why are deeper notes more difficult to produce?
  • Why do we have to use intonation that often?
  • What is end correction and how does it work?

These are some of the questions I was contemplating while enjoying the thermal bath of Harkány. I also discussed these problems with Tamás Horváth, engineer, who became my student. We started brainstorming and working on a solution how the flute sound could be improved. Tamás designed the components digitally, and we had a turner make the first prototypes of these improved headjoints. I practiced and played the flute for many hours to test the new inserts and used the tuner to collect information about their effectiveness. Having worked together for several years, our invention, the “Reform Flute Head” was born and acknowledged by the Hungarian Intellectual Property Office on April 28, 2017.

Why does the 170 years old invention of Theobald Boehm need to be reformed?

Since the creation of the Boehm-flute our world had seen many improvements. The most recent results of the science of acoustics and the opportunities of computer aided design raised new questions, improved our knowledge and created possibilities to investigate the flute further. Acoustic engineers have discovered that the stationary waves occuring in a circular pipe are altered at its end. This alteration is due to the waves’ contact with the air surrounding the body of the instrument. This phenomenon of sound propagation had been defined by two engineers, Norris and Levine, independently from each other. In these studies it has been proven that waves of higher sounds propagate further and waves belonging to lower sounds propagate less from the end of the tube. During these researches It has also been evidenced that the flute is an aerophone instrument with the physical attributes of a cylindrical tube open at both ends.

Having analyzed these studies, I came to the conclusion if the stationary waves propagate from the far end of the flute then they would need proper space to propagate at the headjoint as well. However, the flute’s head is closed by a crown and a stopper. To ensure end correction at the head, the traditional stopper needs to be redesigned. The flat surface used traditionally in a stopper does not correspond with the physical needs of these sound waves, as end correction depends on the pitch of the produced notes. Only a sunken, three dimensional stopper can provide the necessary space for each sound wave. End correction of sound waves is significant, but it only contributes to a few millimeters in practice. By building in a three dimensional stopper, we can have a richer, more harmonious and more resonant sound.

The shape of this sunken surface is of great importance. In the past 40 years there have been several patents experimenting with a new three dimensioned stopper. Among these American, French, Japanese English and innovations the latest is the Japanese one from 2001. It could have spread since then, however, just as the other previous endeavors, it has not been produced and presented to the world. Why haven’t these inventions introduced to the greater audience? Because they do not procude a better sound than the flat tuner surface.

We have also experimented with several different geometrical shapes. During our investigations the produced sounds have been measured and tested with a tuner. Therefore only such stoppers have been released for further testing which showed better results than the traditional ones.

While perfectioning our tuning plug, we have used materials traditionally known in the production of music instruments such as copper, silver, ebony, grenadilla, cocobolo wood and bones. But we have also applied materials produced by the modern industry like silicone, steel, titanium and zirconium. Both the design and the production of these inserts were aided by a specific software and 3D printing.

We have created headjoint inserts which revolutionize the 170 years old Boehm flute.

Our invention is a four segment flute head, which is radically different from the traditional heads.

Both flautists and their audience notice the difference in the music, and these new attributes are also measurable.

Our testers have confirmed the benefits of the new headjoints, and the positive attributes have also been validated by the official report of the acoustic investigations performed by the Budapest University of Technology and Economics.

The invention consists of the following units

  1. Stopper
  2. Crown
  3. Weight (Reinforcing element bounding the embouchure hole)
  4. Non-standard, extended headjoint


Our improved stopper is characterized by a specific three dimensional cylindrical body.

  • The most significant part of our invention is the surface of the stopper. As opposed to the traditional flat surfaced tuning plugs, our version has a three dimensional cylindrical body. As the tuning surface is responsible for the overall frequency of the instrument, we have designed stoppers of various sizes.
  • While the flute’s timbre depends on the stopper’s surface, overall volume is influenced by the quality and the composition of the stopper’s material. We have worked with various materials and created both homogenous and alloyed tuning plugs. Stoppers are available on the market in different materials. We have also used various types of wood and bone besides metal alloys.
  • When comparing our innovation to a traditional flute, the instrument comprising the improved stopper and crown has a much better sound quality. Phonation is easier. The same amount of in-blown air results in a stronger, more dynamic, much clearer and more flexible sound. It has become a lot easier to play forte or piano. The flautist has been freed from unnecessary tone compensation; intonation is simple and smooth.
  • Large-interval slurs and leaps can also be performed easier. It does no longer pose any difficulty to play low notes loudly and high notes softly. Our stopper makes a difference. We provide a wide range of selection from which anyone – from beginners to professionals – can find the stopper most fit for their needs.


The present invention (applying a cylindrical stopper and an open crown) makes the threaded sleeve obsolete. The new conical, tube-like crown enhances musical perception on the left ear side, as the flute emits sound also in the left-hand direction, helping the flautist control the sound even when playing in tutti.


  • The balance weight is to be placed to the resonator cavity between the stopper and the crown.
  • The flute sound can be modified by applying weights made of different materials. Which material is used, depends on the material quality of the flute and on the artistic needs of the flautist. There is a wide range of metals or metal alloys to choose from. Our reinforcing weight balances out the possible weaknesses of the instrument. It can also help produce fuller, richer or more colourful sound, based on the player’s intentions.

Extended headjoint

  • As the cork is removed from the headjoint, there is no direct connection between the stopper and the crown. This innovation enables the production of special, longer headjoints.
  • The extended headjoint can be produced in different geometrical forms.
  • If we want to modify the flute quickly, the innovative headjoint can be connected to the original headjoint, as an external extension. We can choose from a thick or a thin-walled version. This extension can be applied to any flutes.
  • Another option is to build a headjoint longer than the traditional one.
  • The enlarged resonator cavity functions as an amplifier if our innovative open crown is attached to the flute. As the headjoint is longer and the resonator cavity is larger, sound is amplified and more intense.

Our invention can be applied to any type of the Boehm-flutes. Each of the segments may be used individually. It is sufficient to build in only the stopper to student flutes, as this is the most important unit of the invention. When redimensioned properly, the new units can be produced and applied for any transverse flutes, from piccolo to bass flute.

With the help of our invention the flute sounds brighter, fuller, richer and more colourful. By applying the new units, musicians can enjoy an instrument of better quality and of a more resonant sound, with improved dynamics and volume. As one of our volunteers, a professional flautist states: „Less work with the flute but still a more beautiful sound.”

The official sound analysis performed by the Budapest University of Technology and Economics validated our positive experiences: with the improved stopper notes are launched quicker (also while playing lighter) and volume can be greater by 3 to 6 dB. As overtones are richer, the sound of the flute is more powerful and much fuller.

During the tests we have used two different flutes: a Trevor James Cantabile flute with a 925 sterling silver head and a Yamaha 511, closed hole, 800 silver plated flute with a C foot joint.

(original article, Hungarian)