Assembly for transmitting airborne acoustic waves, which can be combined with a musical wind instrument having side holes

Abstract

The invention relates to an assembly (60) for transmitting airborne acoustic waves, configured to be combined with a musical wind instrument having side holes, which instrument comprises a tubular body defining an air column and extending locally substantially along a first axis, the transmission assembly comprising: a device for emission (E) of airborne acoustic waves in the air column, comprising an actuator which is separate from the tubular body and able to transform an electrical signal into airborne acoustic waves; a device for reception (R) of airborne acoustic waves, comprising: a microphone suitable for receiving, after their propagation in the air column, the waves transformed by the actuator, the microphone being positioned off-centre with respect to the first axis; a transformation device suitable for transforming the waves received by the microphone into an electrical signal that is characteristic of a configuration of blocking of the side holes of the instrument.

Description

[0001] The invention lies in the technical field of hybrid wind musical instruments, i.e. wind instruments which can alternately operate in a first acoustic mode and in a second digital mode. The invention applies to all types of wind musical instruments with side holes, including a clarinet, a saxophone, a flute, an oboe, an English horn or a bassoon, this list not being exhaustive. It relates to an assembly for transmitting aerial acoustic waves which can be combined with a musical instrument as mentioned above.

[0002] Acoustic mode of operation is the native mode of operation of a wind instrument. In this mode, sound is produced by vibrations of the instrument's air column triggered by the player's breath.

[0003] A digital mode of operation consists of equipping a wind musical instrument with electronic components which allow the production of digital sounds obtained by a sound synthesis technique applied to one or more electrical signals produced by the components.

[0004] The digital mode of operation of a wind instrument allows, in particular, to make the instrument silent by restoring the digitized sound to the player through headphones. Indeed, acoustic musical practice can be a source of noise pollution and can force a musician to play only during certain times or even discourage him from practicing this instrument.

[0005] Another advantage of digital operation is the expansion of the timbre palette thanks to a sound synthesis technique.

[0006] A problem to be solved in this context is to design a device that can be combined with the acoustic wind instrument and that can be easily reversible so that the user can switch from a digital to an acoustic operating mode.

[0007] Another problem to be solved is to design a device adaptable to the same instrument from different manufacturers, that is to say, which is adaptable regardless of the geometric deviations from one manufacturer to another without modifying the dimensions of the instrument.

[0008] A first approach to silencing an instrument is to attenuate the sound produced by the instrument. Methods for this are known to use absorbent materials such as foam or methods based on attenuation by wrapping. These methods are minimally intrusive and inexpensive but are not sufficiently effective across the entire acoustic spectrum considered. Generally speaking, the sound produced by wind instruments with side holes is more difficult to attenuate than the sound produced by other instruments, for example, brass instruments.

[0009] Another approach to limiting noise pollution is to use a device that replaces the acoustic operation of the instrument, in other words, a fully digital instrument. This type of instrument allows for the simultaneous measurement of breath parameters (intensity and lip pinching) as well as finger position on the instrument. The keys can be static or mechanical. Coupled with a synthesizer, this type of instrument provides a wide range of timbres and is easy to use. Its minimalist technical design makes it a relatively affordable product in terms of cost. However, handling such a device is different from a clarinet or saxophone due to the configuration and mechanical behavior of the keys and mouthpiece.This instrument therefore requires additional and non-shared learning, which is unsatisfactory when the musician wishes to improve his skills with his acoustic instrument.

[0010] A prior art solution consists of inserting a device that is inserted between two upper parts of an instrument, for example between the mouthpiece and the neck of a saxophone, to allow the detection of waves. This solution is not satisfactory because it lengthens the size of the musical instrument and therefore modifies the posture of its user (in particular a backward movement of the head in relation to the position of the arms). Furthermore, the response times announced for this type of solution are more than 100 ms. A response time of this order of magnitude is not satisfactory for the practice of a wind instrument; it must be much shorter, and ideally less than 10 ms. GB 2 537 104 A proposes a system for simulating a wind instrument comprising an ultrasonic transducer and an associated receiver, making it possible to detect the length of the air column based on the reflected or directly received ultrasound.

[0011] US 2020 / 043454 A1 discloses a device to be inserted into the body of a musical instrument of the clarinet type in which an air wave transmitter-receiver pair makes it possible to determine the musical note played in real time.

[0012] Another prior art solution measures the standing wave that is created in the air column following the vibration of the latter by an actuator placed in the upper part of the instrument. The time required to excite this standing wave is of the order of several tens of milliseconds. This is not satisfactory for playing a wind instrument. Ideally, the response time is around 10 milliseconds.

[0013] Another solution uses ultrasonic elastic mechanical waves propagating in the body of the instrument to detect the position of the keys. In this configuration, a transmitter is placed in the upper part in contact with the body of the instrument and a receiver in the lower part. This configuration allows for rapid and smooth detection of notes. However, this solution is sensitive to physical contact exerted on the instrument and results in low detection robustness. For example, FR 3 103 951 A1 discloses a detector of blocking configurations of a wind instrument, comprising fixing means for inserting a transducer into the body of the instrument.

[0014] Finally, a last known solution uses electromagnetic waves of several Megahertz using the tubular structure as a waveguide (emitter at the top and receiver at the bottom). This solution is also sensitive to contacts, the position of the emitter and receiver as well as external disturbances (electromagnetic waves). The waveguide requires a material with low resistivity to maintain good signal integrity. Non-conductive materials limit the wave propagation distance. This solution is therefore unsatisfactory.

[0015] The invention aims to overcome all or part of the problems mentioned above by proposing an adaptable, removable and universal assembly for different instruments capable of generating and receiving aerial acoustic waves in the air column of the instrument, and having a response time of a few milliseconds allowing rapid and fluid detection of notes, compatible with the practice of a wind instrument. In addition, the assembly which is the subject of the invention is insensitive to physical contacts or external disturbances exerted on the instrument (contact on the instrument, variations in ambient temperature). This results in an adaptable, removable and universal assembly having a high robustness of note detection regardless of the external disturbances to which the instrument is subjected.

[0016] To this end, the invention relates to an assembly for transmitting aerial acoustic waves configured to be combined with a wind musical instrument with side holes comprising a tubular body defining an air column, the tubular body extending locally substantially along a first axis, said transmission assembly being intended to be arranged in a removable manner inside the tubular body of the instrument, the transmission assembly being characterized in that it comprises: a device for emitting aerial acoustic waves in the air column comprising: ∘ a first structure for attachment to the tubular body of the instrument; ∘ an actuator capable of transforming an electrical signal into aerial acoustic waves; ∘ an intermediate element for attaching the actuator to the first attachment structure configured to detach the actuator from the tubular body; a device for receiving aerial acoustic waves comprising: ∘ a second structure for attachment to the tubular body of the instrument; ∘ a microphone connected to the second attachment structure, the microphone being capable of receiving, after their propagation in the air column, the aerial acoustic waves emitted by the actuator, the microphone being preferably positioned off-center relative to the first axis;∘ a transformation device connected to the second fixing structure and capable of transforming the aerial acoustic waves received by the microphone into an electrical signal characteristic of a configuration for blocking the lateral holes of the instrument. the tubular body comprising a stop, the first fixing structure comprises a slide, the slide being intended to guide the emission device along the tubular body to the stop. ;

[0017] Advantageously, the intermediate element for fixing the actuator to the first fixing structure is an insulating membrane so as to prevent a transfer of acoustic mechanical waves from the actuator to the tubular body, the intermediate element preferably being made of foam, rubber, or plastic.

[0018] Advantageously, the receiving device comprises a device for positioning the second fixing structure relative to the tubular body.

[0019] Advantageously, the device for positioning the second fixing structure comprises at least three point contacts between the second fixing structure and the tubular body configured to block the receiving device from rotating around the first axis.

[0020] Advantageously, the actuator is a piezoelectric actuator, a piezoelectric chip, a loudspeaker, or an electrodynamic exciter.

[0021] Advantageously, the microphone is a wideband microphone.

[0022] Advantageously, the transmission assembly according to the invention further comprises a device for detecting a position of a key of the instrument connected to the transformation device, preferably at least two magnetometers and a magnetic field transmitter.

[0023] Advantageously, the device for receiving aerial acoustic waves further comprises a loudspeaker connected to the transformation device, said loudspeaker being configured to restore the electrical signal characteristic of a configuration of blocking the lateral holes of the instrument into an audible note.

[0024] Advantageously, the device for receiving aerial acoustic waves further comprises a temperature sensor connected to the transformation device to provide the transformation device with temperature information, the transformation device being configured to take the temperature into account when transforming the aerial acoustic waves received by the microphone into an electrical signal.

[0025] The invention also relates to a side-hole wind musical instrument for selectively producing acoustic sounds and electric sounds, comprising such a transmission assembly.

[0026] In one embodiment of the invention, the instrument is a saxophone or a clarinet or a flute or an oboe or a bassoon.

[0027] The invention will be better understood and other advantages will appear on reading the detailed description of an embodiment given by way of example, a description illustrated by the attached drawing in which: There figure 1 schematically illustrates an example of possible application of the principle of the invention; The figure 2 schematically represents an example of possible positioning of a transmission assembly according to the invention in an instrument; The figure 3 schematically represents an emission device of the aerial acoustic wave transmission assembly according to the invention positioned at the level of the mouthpiece of the instrument; The figure 4 schematically represents a transmission device according to the invention; The figure 5 schematically represents the abutment, in the tubular body, of the first fixing structure of an emission device according to the invention; The figure 6 schematically represents embodiments of the fixing of the actuator on the first fixing structure of a transmission device according to the invention; The figure 7 schematically represents a device for receiving the aerial acoustic wave transmission assembly according to the invention positioned at the level of the bell of the instrument; The figure 8 schematically represents an acoustic signature for a note played with an alto saxophone.

[0028] The invention is intended to be implemented for an application of a method for detecting and locating a disturbance of an environment by means of a system composed of at least one acoustic wave transmitter and at least one acoustic wave receiver coupled to an electronic device which receives and analyzes the signal produced by the acoustic wave receiver to deduce the location of the disturbance. Such a method is known from the prior art, for example international publication WO2016 / 173879.

[0029] In the remainder of the description, we will speak of airborne acoustic waves to designate more broadly the waves compatible with the envisaged application of which ultrasonic waves are part. The frequency range of the waves is preferably between 20 and 40 kHz, or between 20 and 60 kHz or between 20 and 80 kHz or more.

[0030] Furthermore, the invention is described in the example of the saxophone but the invention applies to all types of wind musical instruments with side holes including a clarinet, a saxophone, a flute, an oboe, an English horn or a bassoon, this list not being exhaustive.

[0031] More generally, the invention is described in the field of wind musical instruments. However, the principle of the invention can be applied to any adaptable, removable device to be positioned in a hollow body, such as for example in a pipe with variable geometry or not, in particular for non-destructive testing applications with detection of acoustic activity.

[0032] The present invention relates to an assembly for transmitting airborne acoustic waves configured to be combined with a wind musical instrument with side holes intended to be removably arranged inside the tubular body of the instrument. The interior of the tubular body of the instrument forms an air column. The invention makes it possible to identify the notes played with the instrument from the acoustic signature generated in the air column via the opening or closing of the valves of the instrument. The principle of the invention is based on the excitation of the air column via an actuator, for example piezoelectric, in the ultrasonic spectrum at the neck and the acoustic signature is measured at the bell via a microphone, for example wideband.This arrangement allows detecting the played note in just a few milliseconds while being robust against environmental disturbances such as physical contact on the instrument or ambient noise. Note recognition is performed via a dedicated algorithm (by correlation or classification). The transmission assembly comprises a wave emitting device and a wave receiving device, as explained by means of the figures described below.

[0033] There figure 1 schematically illustrates an example of possible application of the principle of the invention.

[0034] On the left side of the figure 1 a 100 clarinet is shown in a configuration for acoustic playing, that is, an original clarinet. On the right side of the figure 1 , two removable parts of the instrument have been identified: the mouthpiece 105 and the bell 106. These two parts can be removed to configure the instrument in digital mode. To do this, the original mouthpiece 105 is removed and a transmission device according to the invention can be placed in the neck or barrel of the instrument (or directly on the instrument in place of the removable neck or barrel). Similarly, in the original bell 106, a reception device according to the invention can be positioned. The transmission assembly comprises (preferably at the level of the reception device), connected to the outside of the instrument, a transformation device, corresponding for example to a computer or electronic device capable of receiving and analyzing the signal produced by an acoustic wave receiver to deduce the location of the disturbance,connected to the transmitters and receivers to implement a method for detecting and identifying the plugging state of the holes of the instrument. The transformation device is designed to implement the actions detailed below. It comprises a processing unit for executing instructions from a computer program to implement these actions. But it could be replaced by an electronic device composed solely of electronic circuits (without a computer program) to carry out the same actions. Generally speaking, a method for detecting and identifying the plugging state of the side holes of a wind musical instrument comprises a first learning phase in which a plugging state of the holes of the instrument is activated from among the set of possible states,aerial acoustic waves are propagated in the instrument from the transmission device located on the instrument (preferably at the level of the mouthpiece or the neck / barrel), the aerial acoustic waves are captured by the reception device of the transmission assembly of the invention and certain characteristics of the captured signal are saved in a library, this first phase being iterated on all the plugging states of the holes of the instrument corresponding to its chromatic tablature, and a second detection phase in which the player activates a plugging state of the holes of the instrument to produce a corresponding note,the airborne acoustic waves transmitted by the transmitting device and to the receiving device are captured again and certain characteristics of the captured signal are compared with the corresponding characteristics in the library to deduce which hole plugging state is activated and then deduce the corresponding score. Those skilled in the art may refer to various prior art documents to implement one or more variants of the method for processing the signal produced by one or more elastic mechanical wave receivers.,

[0035] The mouthpiece can also be a modified mouthpiece that can be connected to the computer device integrated into the bell and include a device for detecting the player's breath. In this way, it is possible to synchronize the digital reproduction of the notes with the player's breath.

[0036] The computing device provides a computer with the notes associated with the detected hole plugging states. The computer performs a sound synthesis method to digitally reproduce the notes to a user by means of a headset 202. The computer may be embedded in a computer 200 or a smartphone 201 or any other equivalent electronic device.

[0037] Details of detecting and identifying the plugging pattern of the side holes of the instrument are available in the prior art, for example international publication WO2016 / 173879. The present invention relates to the transmitter and receiver device usable in such detection.

[0038] There figure 2 schematically represents an example of possible positioning of a transmission assembly 60 according to the invention. The transmission assembly 60 of aerial acoustic waves is configured to be combined with a wind musical instrument 100 with side holes comprising a tubular body 101 defining an air column 103. The tubular body 101 extends locally substantially along a first axis X, and said transmission assembly is intended to be removably arranged inside the tubular body 101 of the instrument 100. The transmission assembly 60 comprises a wave transmission device E and a wave reception device R. The transmission device E, called transmitter, is preferably positioned in the neck of the instrument 100 and the reception device R, called receiver, is preferably positioned in the bell of the instrument 100.The invention is therefore based on a transmission of an acoustic signal via the air column, a transmission of data between receiver and computer (receiving device R), and a transmission of data between the computer (receiving device R) and the transmitter (transmitting device E).

[0039] As will be detailed below, the positioning of the transmission assembly in the body of the instrument allows the initial geometry of the instrument to be preserved. In addition, such a transmission assembly does not cause any discomfort in handling the instrument since it is positioned in the body of the instrument.

[0040] The transmission device E called transmitter and the reception device R called receiver with communication devices between them, communication which can be wired, but preferably wireless, constitute a transmission assembly 60.

[0041] There figure 3 schematically represents an emission device E of the transmission assembly 60 of aerial acoustic waves according to the invention positioned at the level of the beak of the instrument. The emission device E of aerial acoustic waves in the air column 103 comprises: a first fixing structure 10 to the tubular body of the instrument; an actuator 11 capable of transforming an electrical signal into aerial acoustic waves; an intermediate fixing element 12 of the actuator 11 to the first fixing structure 10 configured to detach the actuator 11 from the tubular body.

[0042] The actuator 11 is any type of actuator capable of generating airborne acoustic waves. For example, the actuator may be a piezoelectric actuator, a piezoelectric chip, a loudspeaker, or an electrodynamic exciter.

[0043] The intermediate fixing element 12 of the actuator 11 to the first fixing structure 10 is an insulating membrane so as to prevent a transfer of acoustic mechanical waves from the actuator 11 to the tubular body 101, the intermediate element 12 preferably being made of foam, rubber, or plastic.

[0044] A player will blow into the conventional connector of the mouthpiece 8 via an instrumented mouthpiece. It can be noted that the player can also be in continuous mode without blowing into the instrument. The set 9 of sensors and electronic elements for detecting the breath transcribes the breath into an electrical signal. This electrical signal powers the actuator 11 which then generates aerial acoustic waves. Alternatively, in order not to waste time in recognizing the notes, the acoustic signals are preferentially generated continuously, and it is the sound synthesis which is activated by the player's breath. These waves will move only in the air column 103. In other words, no wave circulates via the tubular body 101. The intermediate element 12 acts as an insulator. While serving as a means of attaching the actuator to the first structure 10, it makes it possible to separate the actuator from the tubular body 101.The actuator 11 is therefore isolated from the tubular body. The movements of the actuator 11 intended to generate waves are not transferred to the tubular body thanks to the wave-absorbing action of the intermediate element 12. The actuator 11 can have the shape of cymbals, which makes it possible to increase the amplitude of the emitted signal.

[0045] There figure 4 schematically represents an emission device E according to the invention. In this figure, a possible positioning of the elements of the emission device E can be seen in detail. The first structure 10 is positioned in the upper part of the tubular body of the instrument. On this first structure 10, the actuator 11 is oriented towards the air column 103. The actuator 11 is connected to the first structure 10 by the intermediate fixing element 12. The intermediate element 12 completely isolates the actuator from the first structure 10 and from the tubular body 101.

[0046] The tubular body 101 comprises a stop 102. The first fixing structure 10 comprises a slide 14, the slide 14 being intended to guide the emission device E along the tubular body 101 to the stop 102. Thanks to the slide 14, the emission device E is blocked in translation and in rotation in the body of the instrument. Thus, the first structure 10 is positioned in the jar of the instrument, in a fixed and always identical manner for the same instrument.

[0047] There figure 5 schematically represents the abutment, in the tubular body 101, of the first structure 10 for fixing a transmission device E according to the invention. The tubular body 101 of a saxophone comprises a stop 102. This stop is present in all saxophones. The slide 14 is intended to guide the emission device along the tubular body 101 to the stop 102. In other words, the emission device is first positioned in the upper part of the tubular body 101 (shown in solid lines on the left part of the figure), then slides in the tubular body 101 until the entrance of the slide 14 meets the stop 102. The slide 14 and the stop 102 cooperate, which ensures the angular positioning of the emission device E in the tubular body 101. The slide 14 also plays the role of guiding the emission device E in the tubular body 101 until it abuts against the stop 102.The transmitting device E is then in its final fixed position for use (shown on the right part of the dotted figure).

[0048] There figure 6 schematically represents embodiments of the fixing of the actuator 11 on the first structure 10 for fixing a transmission device E according to the invention. The central representation shows that the actuator 11 can be positioned within the intermediate element 12 which then takes the form of a ring, in a hollow portion of the first structure. The representation on the left shows the same configuration and shows the stop discussed previously to correctly position the transmission device relative to the instrument. The representation on the right shows the possibility of considering an intermediate element 12 in contact with the tubular body. This configuration is made possible by the fact that the intermediate element has a strong insulating role and blocks the transmission of waves from the actuator 11 to the tubular body.It is important to remember that the invention is based on the transmission of airborne acoustic waves via the air column in the tubular body of the instrument, and no elastic mechanical waves are to be transmitted via the tubular body of the instrument.

[0049] There figure 7 schematically represents a receiving device R of the transmission assembly 60 of aerial acoustic waves according to the invention positioned at the level of the bell of the instrument. It is considered here that the tubular body 101 extends locally, at the level of the bell, substantially along a first axis X, as represented in the figure 7 . The device R for receiving aerial acoustic waves comprises: a second fixing structure 20 to the tubular body of the instrument; a microphone 21 connected to the second fixing structure 20, the microphone 21 being able to receive, after their propagation in the air column, the aerial acoustic waves emitted by the actuator 11, the microphone 21 being preferably positioned off-center relative to the first axis X; (in a variant, the microphone can be positioned centered relative to the first axis X) a transformation device 30 connected to the second fixing structure 20 and able to transform the aerial acoustic waves received by the microphone 21 into an electrical signal characteristic of a configuration of blocking the lateral holes of the instrument.

[0050] The microphone 21 is preferably, but not necessarily, a wideband microphone.

[0051] The receiving device R advantageously comprises a device 22 for positioning the second fixing structure 20 relative to the tubular body 101. Thus the receiving device R is blocked in translation and in rotation in the bell. The second structure 20 is positioned in the bell of the instrument, in a fixed and always identical manner for the same instrument.

[0052] In one embodiment, the positioning device 22 of the second fixing structure 20 comprises at least three point contacts 23 between the second fixing structure 20 and the tubular body 101 configured to block the receiving device R in rotation about the first axis X. One of the point contacts may comprise a screw which, once turned, is fixed on a part of the tubular body. Alternatively, a central screw system may, on a rotation, deploy strips from the second structure towards the tubular body to constitute point contacts in order to block the degrees of freedom of the receiving device R.

[0053] The receiving device R of the invention therefore comprises a rigid element (second structure 20) fixed to the bell of the instrument with adaptation elements for different sizes of instruments as explained previously. The receiving device R comprises a broadband microphone type sensor capable of measuring ultrasonic waves and preferably placed off-center from the first axis X in order to break the symmetry of the acoustic waves and to increase the richness of the acoustic signature specific to each note and therefore to each position of the valves. The offset of the microphone 21 relative to the first axis X makes it possible to avoid destructive wave interference. Thanks to this configuration, good wave detection is guaranteed.

[0054] The control electronics and batteries may be placed inside a hollow cylindrical body associated with the second structure. Optionally, a reference rod may be placed on the second structure 20 attached to the horn to indicate the correct angular placement of the receiving device R with respect to the instrument. This rod then touches the instrument at a position chosen by the user and serves as a placement guide. This rod may be retractable.

[0055] The transformation device 30 is for example positioned in the hollow body of the second structure 20. It is connected to the microphone to process the aerial acoustic waves received by the microphone after their propagation in the air column, with the aim of being processed to generate an electrical signal characteristic of a configuration for blocking the lateral holes of the instrument. A computer device can be connected to the transmission assembly (transmission or reception). The computer device is then able to provide a control signal to the transmitting transmission assembly which then transmits waves and the receiving transmission device receives these waves which its microphone transmits to its transformation device into a reception signal from the received waves. Alternatively, the computer device is part of the transformation device.Thus, the transformation device is designed to detect and recognize the acoustic signature of the blockage state from the reception signal corresponding to the received acoustic waves, that is to say to the acoustic waves emitted by the emitting device E and which have propagated in the air column of the instrument. The detection method to be implemented therefore requires the transmission assembly to be correctly positioned in the tubular body 101.

[0056] More specifically, the transformation device 30 is configured to: performing a first learning phase consisting of varying the configurations of the blocking state of the side holes of the instrument among the set of possible configurations and recording, for each configuration, at least one reference characteristic of the reception signal, performing a second monitoring (or use) phase while a user plays said musical instrument consisting of recording, for each note played by the user, at least one current characteristic of the reception signal equivalent to said reference characteristic, and comparing the current characteristic to the set of recorded reference characteristics to deduce therefrom the blocking configuration of the holes of the instrument actuated by the player.

[0057] The transmission assembly 60 according to the invention is based on the transmission of aerial acoustic waves via the air column in the tubular body while ensuring a response time compatible with the practice of the musical instrument.

[0058] The invention is based on using a transmitting device in the upper part of the instrument and a receiving device in the lower part of the instrument. Note that the invention is also applicable by reversing the transmitting device and the receiving device, that is to say with the transmitting device in the lower part and the receiving device in the upper part of the instrument. A frequency sweep covering the ultrasonic spectrum between 20kHz and 80kHz generates waves via a piezoelectric actuator or an electrodynamic actuator. These waves move in the air column of the instrument. The position of the valves modifies the propagation of these waves and generates a specific signature for each note played. This ultrasonic acoustic signature is measured in the lower part of the instrument with a receiving device such as a microphone.A classification algorithm is used to recognize the played note and create an artificial equivalent note via sound synthesis. The classification is done using a reference established during a calibration or learning phase at the beginning of the hybrid instrument's use.

[0059] The invention differs from prior art solutions that use the body of the instrument, and for which two effects can hinder the correct classification of notes. First, physical contact (arm, leg, fastening strap, headphone cable, etc.) outside the instrument can be considered as a disturbance and therefore assimilated to a closed valve. The recognized note is therefore not exact. A second disturbing factor in prior art solutions using the body for wave propagation is a temperature variation between the learning phase and the classification phase. A higher or lower temperature shifts the position of the resonances of the structure and therefore modifies the acoustic signature. Classification then becomes impossible.

[0060] In the invention, by using the air column as a means of propagating ultrasonic waves, the transmission assembly is insensitive to audible noise and physical contact. The influence of temperature is a priori less than in the case of elastic mechanical waves. The transmitter couple in the upper part and the receiver in the lower part of the instrument allows to maintain good responsiveness of the detection of keys / notes because the wave propagation time is only a few milliseconds (2.5 ms for an alto saxophone). In order to favor air waves, the actuator is decoupled from the body of the instrument (therefore there is no coupling of the actuator with the body of the instrument). The sensor that measures the air waves is preferably placed outside the central axis of the tubular body of the instrument. This breaks the symmetry of the acoustic waves and makes the acoustic signature richer. This allows to better distinguish the different notes.

[0061] Advantageously (and as is visible on the figure 2 ), in a possible embodiment, the transmission device E may comprise a device 51 for detecting a position of a key of the instrument 100 connected to the transformation device 30, preferably at least two magnetometers 52 and a magnetic field transmitter 53, for example a magnet. This device is schematically represented on the figure 2 . In order to detect the position of the octave key, a magnetic field transmitter 53 can be clipped near the octave key. At least two magnetometers 52, advantageously three, are positioned inside the deformable structure 10 of the transmission device E at different angles. Indeed, from these different positions, it is possible to detect the octave key, regardless of the saxophone used. The transformation device 30 is configured to read the value of the magnetometers and records for each the maximum variation range of the signal. This contains the extreme values ​​due to the displacement of the octave key, but also to the noise. The magnetometer which has the greatest variation is selected. Then, a hysteresis threshold is chosen at a certain percentage of this signal range. Thus, depending on whether the measurement is above or below the chosen threshold, the octave key is read as activated or not.

[0062] The transmission assembly according to the invention can be adapted to different instruments which have varied bell shapes.

[0063] In another embodiment, the device R for receiving aerial acoustic waves may further comprise a loudspeaker (for example arranged on the second structure, outside the instrument) connected to the transformation device 30, said loudspeaker being configured to restore the electrical signal characteristic of a configuration of blocking the lateral holes of the instrument into an audible note.

[0064] The transmission assembly according to the invention allows the transmission via the air column of the signal generated by the actuator (at the level of the transmitting device), the mechanical locking of the transmission assembly by contact points ensuring only the positioning and the maintenance in position (with rotation stop), a system for detecting the activation of the octave key, associating for example and in an illustrative manner a magnetic measurement and a discrimination algorithm.

[0065] Furthermore, the transmission assembly according to the invention allows the reception of the transmitted waves (at the receiving device) through the air column of the instrument, the positioning and maintenance in position of the transmission assembly in the tubular body of the instrument without modification of the instrument or hindrance during use of the instrument with fixing structures adapting to the different instruments, communication between the transmission devices, processing of the information thanks to the transformation device, and finally energy autonomy thanks to the installation of a battery in the transmission assembly (preferably in the receiving device for reasons of space requirement).

[0066] There figure 8 schematically represents an acoustic signature for a note played on an alto saxophone. This is an example to represent the order of magnitude of the propagation and reception times of waves. The instant t0 represents the start of the emission. At t0 + 2.25 ms the start of reception takes place. The duration of 2.25 ms corresponds to the propagation time of the signal in the air between the neck and the bell. The end of reception takes place at t0 + 2.25 ms + 5 ms.

[0067] In order to have good reactivity, excitation in the ultrasonic spectrum is preferred. This allows for a quasi-steady state to be achieved more quickly than in the audible spectrum. For example, the note "A" at 442 Hz has a period of 2.26 ms. A quasi-steady state can be considered after approximately 10 periods. This gives a delay of 22.6 ms to detect such a note using the audible spectrum. Using a frequency of 30 kHz, the period is reduced to 0.033 ms. This therefore gives a delay of 0.33 ms for 10 periods. In this case, it is the speed of sound (and therefore the time required for the sound to reach the receiver) that dictates the minimum detection delay.

[0068] Typically, a frequency sweep from 20kHz to 40kHz for an alto saxophone emitted by the piezoelectric actuator generates an ultrasound that travels in the air column. After a signal propagation time in the air between the neck (transmitting device) and the bell (receiving device) of about 2ms, the sound is recorded by the receiving module (as shown in the figure 8 ). The transmission signal is modified by the air column and the position of the flaps. Upon reception, this signal has a unique acoustic signature. This signature can be compared either by an SVM type algorithm, short for Support Vector Machine or support vector machines (or more broadly a machine learning algorithm) or by a deterministic algorithm with the acoustic signature of the calibration in order to recognize the note played.

[0069] In one embodiment, the device R for receiving aerial acoustic waves further comprises a temperature sensor connected to the transformation device 30. This sensor is preferably arranged in the hollow body of the second structure. The temperature sensor makes it possible to measure the temperature of the air in the air column.

[0070] It has been found that the ambient temperature can influence note detection depending on the temperature variation ranges. Indeed, the method for detecting and identifying the state of plugging of the instrument's holes operates optimally for a certain temperature range, for example at room temperature of 20°C, which corresponds to the room temperature during calibration. The method for detecting and identifying the state of plugging of the instrument's holes therefore ensures perfect reproduction of the notes if this method is used at this temperature. If the instrument is used at a different temperature (for example following storage in a car trunk exposed to the sun), note detection will be affected. The applicant carried out tests by exposing a saxophone to a high temperature and then using, in a room at 20°C, the method for detecting and identifying the state of plugging of the holes.Some notes are not correctly identified, and it takes 1h30 for a return to normal. This means that a re-calibration would be necessary. The presence of the temperature sensor in the transmission assembly of the invention makes it possible to have the information on the temperature in the use phase of the detection method. It has been observed that an increase in temperature translates the frequency spectrum. In the presence of the temperature sensor, it is therefore possible to make the frequency spectrum coincide with that at 20°C (or any other reference temperature corresponding to the temperature of the instrument during the learning phase). The frequency spectrum translation factors can be previously studied once only during the learning phase. There is one factor per temperature for a given instrument. Then, this factor is applied in real time during the use phase.This eliminates the need to recalibrate the process every time the temperature changes.

[0071] Note that the aspects presented above make the transmission assembly as robust as possible. But this requires at least one specific calibration per instrument. A modification of the instrument or a slight defect such as a bump therefore requires a new calibration since the transmission of waves via the air column will be impacted. A re-calibration procedure can be implemented which takes as a reference an audible sound and in this case a real note which serves as a reference. Alternatively, or in addition, it is also possible to carry out a classic calibration made using only the ultrasonic spectrum. This makes it possible to re-calibrate the associated transfer function in the ultrasonic spectrum. For this recalibration, a frequency sweep which covers the audible spectrum and the ultrasonic spectrum must be carried out.

[0072] The invention also relates to a side-hole wind musical instrument 100 for selectively producing acoustic sounds and electric sounds, comprising a transmission assembly 60 as described above.

[0073] The 100 side-hole wind musical instrument can be a saxophone or a clarinet or a flute or an oboe or a bassoon.

Claims

1. An airborne acoustic wave transmission assembly (60) configured to be combined with a musical wind instrument (100) with side holes comprising a tubular body (101) defining an air column (103), the tubular body (101) extending locally substantially along a first axis (X), said transmission assembly being intended to be disposed removably inside the tubular body (101) of the instrument (100), the transmission assembly comprising: - a device (E) for emitting airborne acoustic waves in the air column (103) comprising: ∘ a first fixing structure (10) at the tubular body of the instrument; ∘ an actuator (11) capable of transforming an electrical signal into airborne acoustic waves; ∘ an intermediate element (12) for fixing the actuator (11) to the first fixing structure (10) configured to separate the actuator (11) from the tubular body; - an airborne acoustic wave reception device (R) comprising: ∘ a second fixing structure (20) at the tubular body of the instrument; ∘ a microphone (21) linked to the second fixing structure (20), the microphone (21) being capable of receiving, after the propagation thereof in the air column, the airborne acoustic waves emitted by the actuator (11), the microphone (21) being positioned preferably off-centre with respect to the first axis (X); ∘ a transformation device (30) linked to the second fixing structure (20) and capable of transforming the airborne acoustic waves received by the microphone (21) into an electrical signal characteristic of a plugging configuration of the side holes of the instrument, - characterised in that the tubular body (101) comprises a stop (102), and in that the first fixing structure (10) comprises a guideway (14), the guideway (14) being intended to guide the emission device (E) along the tubular body (101) to the stop (102).

2. The transmission assembly (60) according to claim 1, wherein the intermediate element (12) for fixing the actuator (11) to the first fixing structure (10) is an insulating membrane so as to prevent a transfer of acoustic mechanical waves from the actuator (11) to the tubular body (101), the intermediate element (12) being preferably made of foam, rubber or plastic.

3. The transmission assembly (60) according to any one of claims 1 to 2, wherein the reception device (R) comprises a device (22) for positioning the second fixing structure (20) with respect to the tubular body (101).

4. The transmission assembly (60) according to claim 3, wherein the device (22) for positioning the second fixing structure (20) comprises at least three spot contacts (23) between the second fixing structure (20) and the tubular body (101) configured to block the reception device (R) in rotation about the first axis (X).

5. The transmission assembly (60) according to any one of claims 1 to 4, wherein the actuator (11) is a piezoelectric actuator, a piezoelectric pad, a loudspeaker or an electrodynamic exciter.

6. The transmission assembly (60) according to any one of claims 1 to 5, wherein the microphone (21) is a wideband microphone.

7. The transmission assembly (60) according to any one of claims 1 to 6, further comprising a device (51) for detecting a position of a key of the instrument (100) linked to the transformation device (30), preferably at least two magnetometers (52) and one magnetic field emitter (53).

8. The transmission assembly (60) according to any one of claims 1 to 7, wherein the airborne acoustic wave reception device (R) further comprises a loudspeaker (40) linked to the transformation device (30), said loudspeaker (40) being configured to render the electrical signal characteristic of a plugging configuration of the side holes of the instrument as an audible note.

9. The transmission assembly (60) according to one of claims 1 to 7, wherein the airborne acoustic wave reception device (R) further comprises a temperature sensor linked to the transformation device (30), to supply the transformation device with temperature information, the transformation device being configured to take into account the temperature when transforming the airborne acoustic waves received by the microphone into an electrical signal.

10. A side-hole musical wind instrument (100) for selectively producing acoustic sounds and electric sounds, comprising a transmission assembly (60) according to any one of claims 1 to 9.

11. The side-hole musical wind instrument (100) according to claim 10 wherein said instrument is a saxophone or a clarinet or a flute or an oboe or a bassoon.

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