FR2775823A1 - Electro-acoustic reed for musical instrument - Google Patents

Abstract

The electro-acoustic reed for a musical instrument has an oscillating duct (4) into which the body of the instrument is placed and a microphone (1) in a cell in communication with the duct. The microphone is connected to an amplifier (2)

Description

i

  The present invention relates to an electro-tip device

  active acoustics intended to be placed on an original adapted musical instrument or an existing wind instrument allowing it to be played. The device according to the invention will therefore be naturally named: "electro-acoustic reed" The electro-acoustic oscillator with "Larsen" effect (sustained oscillations obtained when a microphone is approached from a speaker connected to the same amplifier) is known and has been the subject of numerous studies, most often for

  avoid this undesirable effect in a sound system.

  In the field of non-linear acoustics, inspired by the work of the physicist Mitchell J. FEIGENBAUM on non-linear systems and transformations published in 1978 (JOURNAL OF STATISTICAL PHYSICS 19 (1). 1978, 25-52) then in 1983 (PHYSICA 7D.1983, 16-39), three Japanese physicists, M. KITANO, T. YABUZAKI and T. OGAWA will realize an electroacoustic oscillator with elementary "Larsen" effect to study experimentally doublings of oscillatory periods and

  the culmination of chaos. (PHYS. REV. Let 50 (10), 1983, 713-717).

  In 1983 numerous scientific publications on the study

  chaos and doubling of periods will follow one another.

  On June 14, 1985, Mr Christian MAGANZA defended a doctoral thesis in applied acoustics dealing with non-linear exitations of a cylindrical acoustic duct and observations of period doublings preceding chaotic behavior with an application proposed on the clarinet. (Academy of

  Nantes, University of Maine, Faculty of Science).

  During the experiments carried out, the author of this thesis uses the "Larsen" effect in an oscillator to apply the theories of FIEGENBAUM on a scenario leading to chaos. He uses it on a cylindrical pipe then on a clarinet to experiment and

  analyze period doublings on the instrument.

  In the field of musical acoustics, specific to the present invention, the electro-acoustic oscillator with "Larsen" effect has so far never been used and adapted in the production of a fully-fledged electroacoustic reed intended for either to build an original musical instrument, or to be mounted on an existing instrument (Saxophone, flute,

  bagpipes, oboe ...), allowing you to play it.

  The realization of the prototype described below shows experimentally that the construction of an electro-acoustic reed associated with an original musical instrument body is possible by having some knowledge in invoice

  wind instruments as well as basic electronics.

  Note: The prototype was made to play particular works (traditional Irish music), its tone is

therefore fixed in D.

  Furthermore, the similarity of the body of the instrument with a body of flute or clarinet is such that it is sufficient to show that the design of an electro-acoustic reed of the same type adapted to an existing wind instrument and allowing 'play it

  is perfectly possible within the framework of the present invention.

  This by simply obtaining the same frequency response, without particularly seeking to imitate the original sound, the dressing of the sound produced can be achieved outside the oscillation loop by

a digital synthesizer.

  The electro-acoustic reed is constituted by an oscillating loop composed of an acoustic conduit at the open of which the body of the musical instrument will be placed, a microphone or pressure sensor positioned in a cell in communication with leads him. The signal from the microphone sensor is then processed by a suitable amplifier and the latter is connected to a loudspeaker, a transducer or any other electro-acoustic sound source, the mechanically active part of which opens into the acoustic conduit.

previously cited.

  Note: The electro-acoustic sound source can take, according to particular embodiments, multiple forms other than those of a loudspeaker; for example, taking inspiration from the mechanics of the clarinet reed, an electro-acoustic reed as shown in figure 9 can be produced using an original sound source (20) The oscillation frequency can then be adjusted to using the body of the musical instrument by plugging and opening the

  game and octaviation holes.

  The body of the musical instrument can be adapted to a given electro-acoustic reed (as is the case in the embodiment presented below for reasons of greater simplicity); this body may have a cylindrical, cylindrical stepped or conical bore. Secondly, the electro-acoustic reed can be adapted to a wind instrument

given.

  According to particular embodiments - The oscillation loop can include a device for processing the

  digital signal fast enough.

  - The acoustic duct can also have mechanical acoustic filters such as passive resonant cavities, a flow rolling mill or an actuated mechanical reed

  by the flux coming from the electro-acoustic sound source.

  - The instrument for its part can play on an octave, the others being obtained by a frequency multiplier actuated by the

musician, or over several octaves.

  - The set can be miniaturized or enlarged according to the tone

  desired and the maximum space required.

  - Of course, both the reed and the instrument can be made in

  wood, metal or plastic.

  The accompanying drawings illustrate the invention: Plate 1/5 shows the schematic of the electro reed

  -acoustics and 2 significant variants.

  Figure 1 shows the basic diagram, Figure 2 a variant with filters in the main oscillation loop and Figure 3 shows a variant with a differential amplifier

  provided with a filtered feedback loop.

  Legend: (1) Pressure sensor, or microphone (2) Amplifier (3) Electro-acoustic sound source (4) Acoustic pipe (5) (6) (7) Filters (8) Differential amplifier Plate 2/5 figure 4 shows an embodiment of the electro-acoustic reed mounted on an instrument body with a suitable cylindrical bore. Legend: (9) Speaker 8 Ohm / 1W / Diam. 50mm (10) Electret microphone (11) Instrument body (partial view) (12) Flow rolling mill (13) Passive resonant cavity (14) Support sleeve (15) Fitting (16) Main reed duct La Plate 3/5 shows an embodiment of an instrument body

  suitable for the reed of board 2/4.

  Figure 5 shows the instrument body, Figure 6 shows the

  mounting the reed on the instrument.

  Legend: (17) Octaviation piercing (18) Tone adjusting piercing (19) Bell Plate 4/5 shows a practical realization of the electronic part according to the principle of figure 7 and detailed by

figure 8.

  Plate 5/5 shows an example of a sound source used on

  the electro-acoustic reed other than a conventional speaker.

Legend:

(20) Clarinet type sound source.

  The embodiment described here is that of the basic prototype of the simplest electro-acoustic reed having worked and shown good stability (variant using a differential amplifier with filter on the feedback loop and described in Figure 3 ). The choice of prototype was made by favoring ease of reproduction over aesthetics, which results in a somewhat rustic model. For the same imperatives of simplicity the body of the instrument shown here as an example

  (Figure 5) has been adapted to the reed.

  Much of the work has been devoted to expanding the frequency domain of a "Larsen" effect oscillator. The mechanical production of the electro-acoustic reed prototype is detailed in FIG. 4, this one as the body of the instrument (11) were made in PVC for the support sleeve (14) and in PVC-C for the remains so as to have inexpensive and readily available standardized fittings and tubing. The loudspeaker (9) selected is an HP 8 Ohm / 1W in current diameter 50mm (The reed also works very well with an HP 8 Ohm of 0.25W in diameter 50mm, paying attention to the gain ...). This speaker is placed at the top of the reed (Board

2/5).

  Experimental results show that to obtain the widest possible frequency band it is essential that the active part of the sound source is completely opposite the acoustic conduit. To use standard equipment (Minimum diameter of a current speaker of acceptable power = 50mm) on an instrument of reasonable dimensions (Diameter of the instrument body <30mm) it is

  necessary to make certain adaptations.

  The conduit (16) must therefore come as close as possible to the diaphragm of the loudspeaker (9) without touching it. To dampen any sound wave coming from the periphery of the loudspeaker, an annular cavity (13) is formed in the sleeve (14) and plays the

  role of adapted passive acoustic load.

  In the whistle of a recorder, just before its passage in front of the blade, the flow of blown air must be laminated so as to locally increase the speed of flow; this mainly allows to widen the frequency range in which the instrument will play. To do this, we introduce into the body of the spout

  of flute a cylindrical fishplate on which a counterbore is carried out.

  This device is perfectly transposable to the electro-acoustic reed, and the experimental results show a very significant widening of the bandwidth of the reed (up to doubling of the latter). The part (12) therefore acts as

  flow rolling mill in the duct (16).

  The microphone sensor (10) is placed in the support sleeve (14) on an axis normal to that of the conduit (16). Conduit / microphone communication. is made by an orifice drilled in (16) as small as possible to limit the related interference. The position of the axis of the microphone sensor (10) was determined by a series of experiments always favoring the bandwidth of the system, but this time around an average frequency of 410 Hz. The rest of the mechanical construction does not pose

of particular problem.

  The realization of the electronic part is detailed on plate 4/5, the solution adopted for the electro-acoustic reed prototype obeys the schematic of principle of figure 7 (equivalent of the variant presented in figure 3). The construction details are presented in Figure 8: On a classic application diagram of the TDA 2003 integrated differential amplifier, a high-pass filter is placed on the feedback loop in order to obtain a certain "relaxation" the behavior of the amplifier in the frequency domain of the instrument, always with the aim of extending this frequency range. Its cutoff frequency is f0 = 408Hz average frequency of the instrument. The voltage gain of the amplifier for very low frequencies is 100, this gain will go down

  to practically unity by increasing the frequency beyond f0.

  The invoice for the body of the instrument adapted to the electro-acoustic reed is the subject of sheet 3/5. It is made of PVC-C, a more stable material than PVC, resistant to a wide temperature range, not subject to expansion and easy to machine. The bore of the body of the instrument was determined for a tone in D, the process does not differ in any way from the search for a bore for an instrument with ordinary cylindrical central bore (Irish flute of type "TIN WHISTLE" for example) . The octaviation hole (17) may not exist, in which case (see Figure 8) a frequency doubler can be connected to output S and the control button can be positioned in place of (17)

  (Use of a sensitive button associated with an "Analog.

  swich "type TL607 Texas Instrument recommended).

  As on the blowpipe (sing or levriad) of a bagpipe the tone can be finely adjusted by a

adjustment (18).

  The pavilion (19) is inspired by those mounted on certain South American floats (Quena) and has the role of fictitiously lengthening the instrument, adjusting the tone on another point and stabilizing the behavior of the acoustic duct by avoiding mainly unwanted octaviations (increased

sound pressure level).

  The electro-acoustic reed has a good potential for industrial applications in the field of musical instrument invoicing: Either by adapting it to existing instruments, which would allow in particular to dress the sound produced in an original way, or by producing original instruments adapted to the electro-acoustic reed. The commercial success of such a product can come from several factors: - Placing on the market of original concert instruments (equivalent to the electric guitar for wind instruments) with multiple possibilities and directly adaptable to equipment

  stage or recording studio without worrying about sound recording.

  - Used on existing instruments, the electro-acoustic reed gives a new sound and offers

  unprecedented signal processing possibilities.

  - When using such a device, the musician's approval is real and the tactile feeling of playing on a wind instrument is intact (it is not a cylindrical keyboard but actually a wind instrument that plays) . This kind of reed thus allows to preserve the finesse of the game (ornamentation, sliding, "wawa" effect in jazz, click of a note, obtaining the alterations by 1/2 obturations and tablature combinations ...). The electro-acoustic reed therefore provides all the possibilities of the synthesizer for a wind instrument without the disadvantages of a

keyboard interface.

  - Finally, such a process will allow sick, disabled or even simply elderly people to taste the pleasures of

  wind instruments without having to blow into a reed.

Claims (5)

Claims   1) The electro-acoustic reed intended to be placed on a musical instrument and making it possible to play it, characterized in that it comprises an oscillating loop with "Larsen" effect composed of an acoustic conduit (4) at the open from which will be placed the body of a musical instrument, a microphonic or pressure sensor (1) positioned in a cell in communication with the acoustic conduit (4) and connected to a suitable amplifier (2), the latter controlling an electro-acoustic sound source (3), the mechanically active part of which opens into the conduit (4) previously cited.   2) Device according to claim 1) characterized in that the oscillating loop comprises filters (5), (6) placed upstream or downstream of the amplifier.   3) Device according to any one of claims   previous characterized in that the feedback loop of   the amplifier includes a filter (7).   4) Device according to any one of claims   previous characterized in that the electro-acoustic reed   has a resonant cavity (13).   5) Device according to any one of claims   previous characterized in that the acoustic conduit (16) is provided with a flow rolling mill (12).