Classifications

• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H3/00—Instruments in which the tones are generated by electromechanical means
  • G10H3/12—Instruments in which the tones are generated by electromechanical means using mechanical resonant generators, e.g. strings or percussive instruments, the tones of which are picked up by electromechanical transducers, the electrical signals being further manipulated or amplified and subsequently converted to sound by a loudspeaker or equivalent instrument
  • G10H3/14—Instruments in which the tones are generated by electromechanical means using mechanical resonant generators, e.g. strings or percussive instruments, the tones of which are picked up by electromechanical transducers, the electrical signals being further manipulated or amplified and subsequently converted to sound by a loudspeaker or equivalent instrument using mechanically actuated vibrators with pick-up means
  • G10H3/18—Instruments in which the tones are generated by electromechanical means using mechanical resonant generators, e.g. strings or percussive instruments, the tones of which are picked up by electromechanical transducers, the electrical signals being further manipulated or amplified and subsequently converted to sound by a loudspeaker or equivalent instrument using mechanically actuated vibrators with pick-up means using a string, e.g. electric guitar
  • G10H3/181—Details of pick-up assemblies
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
  • G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H3/00—Instruments in which the tones are generated by electromechanical means
  • G10H3/03—Instruments in which the tones are generated by electromechanical means using pick-up means for reading recorded waves, e.g. on rotating discs drums, tapes or wires
  • G10H3/06—Instruments in which the tones are generated by electromechanical means using pick-up means for reading recorded waves, e.g. on rotating discs drums, tapes or wires using photoelectric pick-up means
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H2220/00—Input/output interfacing specifically adapted for electrophonic musical tools or instruments
  • G10H2220/155—User input interfaces for electrophonic musical instruments
  • G10H2220/165—User input interfaces for electrophonic musical instruments for string input, i.e. special characteristics in string composition or use for sensing purposes, e.g. causing the string to become its own sensor
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H2220/00—Input/output interfacing specifically adapted for electrophonic musical tools or instruments
  • G10H2220/461—Transducers, i.e. details, positioning or use of assemblies to detect and convert mechanical vibrations or mechanical strains into an electrical signal, e.g. audio, trigger or control signal

Definitions

• the present invention relates to an optical detection cell for mechanical vibrations of an object, and a vibration sensor using such a detection cell.
• the invention is particularly interesting for the production of a microphone allowing the amplification of stringed musical instruments; more generally, it can be used for detecting the vibrations of a thread and / or for measuring the tension of a thread.
• An optical detection cell is known in particular from document Dl (US4, 563, 931) for detecting the vibrations of a string of a musical instrument.
• the general principle of this cell is shown diagrammatically in FIG. 1.
• a photoemitter 1 emits a light beam 2 which illuminates the cord 3.
• a photoreceptor 4 receives the light beam emitted by the photoemitter 1 and the drop shadow of the cord 3 which modulates directly the light beam as a function of the vibratory oscillation of the string 3.
• the photoreceptor 4 produces a modulated electrical signal representative of the frequency, timbre and amplitude of the vibrations of the string 2.
• An electronic module 5 controls the transmitter 1 and receiver 4, and processes the electrical signal received from photoreceptor 4.
• the Dl cell is ineffective. It allows only in practice to detect the vibrations of the string in a plane perpendicular to the axis formed by the transmitter and the receiver. It does not take into account the other vibrational planes of the string.
• Curtis et al. propose in document D2 (US 5, 237.126) a sensor using a photoemitter and two photoreceptors each positioned on the sides of an isosceles triangular structure. The signals produced by the two receivers are subtracted to obtain a signal representative of the frequency, the timbre and the amplitude of the vibrations of the string. The sensor thus allows all the vibrational planes of the string to be taken into account and therefore allows better quality electronic transcription.
• the triangle structure allows significant movements in one direction (the height of the triangle), which limits the effects (particular movements and generally large amplitude imposed on a string to obtain a particular sound effect) that it is possible to detect.
• the sensors obtained remain fairly sensitive to their light environment and their quality is degraded when they are used in an environment with high light pollution. such as a performance hall.
• a main objective of the invention is an optical detection cell allowing the detection of movements of large amplitudes of an object whatever the direction of these movements.
• a secondary objective of the invention is to improve the precision and the quality of the analog signal reproduced by the detection cell.
• the main objective of the invention is achieved by a cell for detecting the vibrations of an object comprising a first photoemitter for emitting a light beam on one side of said object, a first photoreceptor and a second photoreceptor.
• Each photoreceptor has a detection surface arranged to receive the light beam modulated by the shadow cast by the object.
• the photoemitter, the first photoreceptor and the second photoreceptor are distributed over an interior section of a hollow tube forming a structure of the cell, the object being placed in the vicinity of the center of said section.
• the main components of the cell in particular light emitters and photoreceptors, are commercially available in miniaturized version. This allows for lightweight cells and very small footprint. The cell can thus be easily integrated in the vicinity of the object whose vibrations are detected.
• each photoreceptor is transformed into an electrical signal representative of the frequency, timbre and amplitude of the object, and capable of being amplified if necessary by conventional means.
• the structure of the cell having a tubular shape, with circular section, the object can have significant movements in all directions of the section of the cell, and no longer only in a preferred direction.
• the cell also includes a second photoemitter.
• the first photoreceptor is arranged to receive a light beam emitted by the first photoemitter and the second photoreceptor is arranged to receive a light beam from the second photoemitter.
• the interior surface of the tube comprises a reflecting zone, so that part of the beam emitted by the first photoemitter is received on the zone reflecting and re-emitted towards the second photoreceptor.
• the two photoreceptors can be located on orthogonal axes of the section of the structure, this makes it possible to detect the two vibratory planes of the object independently of one another.
• One of the photoemitters and one of the photoreceptors can be located on a diameter of the section, on either side of the object.
• the tube may have a longitudinal opening, facilitating the insertion of the object into the cell.
• the photoemitter (s) emit a light beam in the form of a pulse train and the photoreceptor (s) detect the pulse train in synchronism.
• the invention also relates to a vibration sensor, comprising a cell as described above, and a control module for controlling the operation of the cell.
• the sensor comprises several cells mechanically associated together to allow the simultaneous detection of the vibrations of several objects, and a control module for controlling the operation of each cell individually.
• the objects are the strings of a musical instrument, each string being placed in the vicinity of the center of a detection cell.
• the sensor can be supplemented by an appropriate amplifier and / or by an electronic signal processing module capable of transforming the signals produced by each cell in one or more signals conforming to the MIDI communication protocol.
• the sensor according to the invention can independently process each of the strings of the instrument under consideration, thanks to the use of a light emitter per string, and one or more photoreceptors. This gives it polyphonic or stereophonic properties depending on the choice of photoreceptor coupling and allows specific applications, some examples of which will be seen below.
• FIG. 1 already described, is a block diagram of a known optical detection cell
• FIGS. 2 and 3 are sectional views of particular embodiments of a detection cell according to the invention
• FIGS. 4, 5 are sensors with several detection cells adapted to be fixed on a stringed musical instrument
• FIG. 6 is a sensor with a single detection cell adapted to be fixed on a stringed musical instrument.
• a cell according to the invention has a hollow tubular structure, open at its two ends. It is preferably made of opaque or reflective material, so as not to let in light parasitic inside the tube, and preferably in light material.
• a plastic material capable of filtering daylight, a resin, a composite material or a light alloy for example, for a cell used for detecting the vibrations of a string of a musical instrument, the dimensions of the cell are approximately: outside diameter: 7.5 mm, inside diameter: 5.5 mm, height: 6 mm.
• the rope whose vibration is to be detected is positioned approximately in the center of the structure and passes right through the tube.
• the tubular structure 21 of the cell 20 is closed and the rope is inserted into the structure by one of its ends.
• the tubular structure 31 has an opening 27 over the entire height of the tube to facilitate the insertion of the cord into the cell.
• a cell according to the invention also comprises at least one photoemitter 22 and at least two photoreceptors 24, 25 positioned on the inner periphery of a section of the tubular structure 21.
• the cell comprises an electronic module (not shown in FIGS. 2 and 3) ) to control the transmitter (s) and the receiver (s), and process the electrical signals received from the photoreceptors 24, 25.
• the cell comprises two photoemitters 22, 23 and two photoreceptors 24, 25.
• An associated emitter and photoreceptor are positioned at the ends of a diameter of a section of the tubular structure, on either side others of the rope. It is sufficient in practice for the receivers to be placed in the light beam emitted by one or other of the light emitters.
• the relative position of the photoreceptors with respect to each other and with respect to the photoemitters, as well as the opening angle of each photoemitter are chosen so that the light beam emitted by a photoemitter is received by a single photoreceptor and so that each beam illuminates the entire clearance surface 26 of the rope.
• the cell comprises a single photoemitter 22, and the interior surface of the hollow tube 31 is reflective at least in an area 28.
• the reflective surface, on the interior surface of the tube is for example obtained by the application of a reflective paint, by depositing a dielectric reflective coating or by bonding a film of reflective material (silvering, aluminum, etc.).
• the surface 28 can cover the entire interior surface of the tube or only an appropriate area.
• the tube is made of reflective material, its inner surface does not need additional treatment.
• the reflecting surface receives the light beam emitted by the emitter 22 and re-emits this beam towards the receiver 25. The reflecting surface 28 thus replaces the second photoemitter.
• the relative position of the photoreceptors, of the reflecting zone 28 and the opening of the emitter 22 are chosen so that the receiver 24 receives the beam emitted by the emitter 22, so that the receiver 25 receives the beam reflected by the surface 28 and so that the emitted beam and the reflected beam illuminate the entire clearance surface 26 of the rope.
• the two photoreceptors 24, 25 of the cell 30 are placed on perpendicular diameters. We thus distinctly and independently detect the fundamental and the harmonics of the two vibrational planes of the string, independently of each other, which then facilitates the processing of the measured signals.
• the two photoreceptors 24, 25 of the cell 20 are in turn closer to each other and form an angle less than 90 °.
• the signals detected by both of the photoreceptors each contain information relating to the movements of the cord in the two vibrational planes.
• a detection cell comprising more than two receivers, for example three or four, distributed over the interior section of the tube. This provides redundant information on the fundamental and harmonics of each vibrational plane, which then allows more precise digital processing of the signal.
• photoreceptors or photoelectric sensors
• photoconductive properties can be used for the reception of the modulated light signal.
• photoresistors, photodiodes, phototransistors, photodarlington, charge transfer sensors, etc. can be used. ...
• photoemitters may be used for the emission of light.
• Optoelectronic components emitting in the visible or invisible spectrum are preferably used, and adapted to be individually controlled in voltage and / or current to vary the intensity of the light flux emitted. It is possible, for example, to use laser diodes or miniature light-emitting diodes, preferably at low voltage (about 2.3 volts) and at high light intensity.
• OLED Organic Light Emitter Device
• These diodes have the advantage of being able to be produced in the form of a thin and flexible film, particularly well suited for being fixed on a non-planar tubular structure, which can easily include opaque covering zones (by screen printing for example) making it possible to achieve personalized and localized light distribution.
• the beam (s) emitted can be collimated or divergent.
• detection is carried out by synchronous modulation / demodulation.
• the photoemitters generate a light beam in the form of a high frequency pulse train (for example of the order of 44 KHz), and the photoreceptors detect these pulses simultaneously.
• the frequency of the pulses is chosen to be sufficiently large in relation to the frequency of the surrounding signals likely to interfere with the detection cell (signals emitted by various lights, flashes, etc., which generally have fairly low frequencies).
• the cell's electronic module controls each photoemitter and each photoreceptor. It fixes for example the frequency of the pulses of the beams emitted by the photoemitters.
• the electronic module also fixes the light intensity of each transmitter (for example by varying the electric current supplying the transmitter); this makes it possible to adjust the output level of the analog signal produced by the cell and / or to favor the movements of the string in one or the other of the vibratory planes of the cell.
• the electronic module processes the analog signals produced by the photoreceptors to extract the fundamental and harmonics in the two vibrational planes of the string and produce an analog signal representative of the frequency, the timbre and the amplitude of the movements of the string.
• FIG. 6 presents a sensor 60 adapted to detect the vibrations of a string of a musical instrument.
• a shoe 61 of substantially U shape, serves as a support for a trigger guard 62 and a counter trigger guard 63, which can thus slide between the legs of the shoe along the x axis.
• the base 64 of the shoe 61 is fixed on the plate of the musical instrument.
• the trigger guard 62 is of substantially parallelepiped shape, it replaces the trigger guard usually supporting the string of a musical instrument.
• the bridge 62 has notch 65 on the top to accommodate and hold in position the rope 74 and two holes 66, 67 intended to receive two adjustment screws (not shown) provided for adjusting the position of the bridge
• the counter bridge 63 and the bridge 62 can slide relative to each other along the x axis and a means of blocking (for example a screw, not shown) is provided to secure the trigger guard and the counter-trigger guard together, so that it is possible to simultaneously adjust the height of the trigger guard 62 and that of the counter trigger guard 63.
• a housing 73 is provided for a screw (not shown) for locking the trigger guard in position in the shoe after adjustment.
• the bridge guard comprises two blocks 68, 69 of substantially U shape and an axis 70. One end of the axis is fixed to the block 69 and the detection cell 71 is fixed to the other end of the axis.
• the counter-bridge thus serves to position and maintain in position the detection cell with respect to the rope 74, the latter itself being positioned and maintained by the trigger guard.
• the blocks 68, 69 are provided to assemble so as to form an empty space in the middle to let pass (without touching it) the rope to be detected.
• the block 68 comes to bear on the base 64 and two adjustment screws (a single screw 72 is shown) makes it possible to adjust the height along the z axis of the position of the block 69 (and therefore of the cell 71 which is integral) by compared to block 68 and to join the two blocks together.
• the cell 71 is slidably mounted on the axis 70 in the direction y, which makes it possible to adjust the distance between the cell and the bridge, according to the expected amplitude of the vibrations of the string.
• the cell 71 is also pivotally mounted around the axis 70, so as to position the cord 74 approximately at the center of the cell 71. Locking means (not shown) are also provided to secure the cell 71 on the axis 70 after adjustment.
• the shoe, the trigger guard and the counter trigger guard can be made of resin or of a plastic material.
• the pin 71 can be made of metal, for example steel or brass.
• the sensor of FIG. 6 is particularly interesting for its large number of possible adjustments, which make it possible: to optimize the position of the cell 71 relative to the rope in order to obtain an optimal detection of the vibrations of the rope; this is done for example by the manufacturer of the sensor - optimizing the position of the rope in relation to the base of the hoof and the platter of the musical instrument; this adjustment can be carried out by the musician and does not require any knowledge of the operation of the sensor: the trigger guard following the movements of the easel, the position of the cell relative to the string is maintained in the event of a change in the height of the easel.
• FIG. 4 shows a sensor 40 adapted to sound a six-string musical instrument.
• This sensor comprises a confinement box 41 in which six detection cells according to the invention are placed. On its sides, the case of course includes openings adapted to let the strings of the instrument in and out.
• the housing is closed by a cover 43.
• the housing consists essentially of two blocks 46, 47 joined on one side by a hinge 48. In each block 46, 47 are hollowed out half-cylinders adapted to form the bodies of the detection cells when the two blocks are associated. Block 47 lifts to install or change the ropes.
• Two adjustment screws 44, 45 make it possible to fix the box to the instrument 46 and to adjust the height and the inclination of the box, so that the strings are correctly positioned in the center of the light beams emitted by the transmitters of each cell .
• the housing is fixed to the body of the instrument, in the vicinity of a pre-existing bridge of the instrument, the said bridge also serving to position and maintain all of the strings.
• the sensor and the bridge are associated in the same housing, and means are provided for adjusting the position of the detection cells relative to the easel. Thus, if the position of the easel is changed, the position of the sensor is changed simultaneously.
• the electronic modules of each cell are grouped into a single electronic module 42.
• the signals generated by each cell are either used separately for use with the MIDI communication protocol, or combined to produce a single signal. Provision may also be made either to amplify the signals generated by each cell independently of one another (a gain pre-amplifier adjustable by an electronic potentiometer is provided at the output of each cell), or to amplify the signal obtained after combining the signals produced by each cell.
• the DC supply of the detection cells is provided by an electric cell or rechargeable battery (not shown) delivering a voltage of approximately 7 volts.
• an electric cell or rechargeable battery not shown
• the electronic module manages each photoemitter / photoreceptor pair in each cell independently of each other, which makes it possible to obtain different sound effects. For example, it is possible to supply the photoemitters of different cells with currents of different intensities. We thus adjust the light intensity of each transmitter, therefore the level (sound volume) of signal output (produced by a cell) associated with each string and we balance, according to an appropriate choice, the overall sound response of the sensor after amplification.
• the electronic module can also control an equalizer, placed at the output of each detection cell, and controlled by an electronic potentiometer to thus adjust the tone of each string separately.
• an equalizer placed at the output of each detection cell, and controlled by an electronic potentiometer to thus adjust the tone of each string separately.
• - means (a graphical interface for example) to allow a user to ergonomically configure the electronic module (microcontroller, electronic potentiometers, level of battery charge for example), to define a desired setting, to recall a previously set memorized, etc. ;
• the detection cell of the invention can have other applications than the production of sensors for stringed musical instruments.
• the cell could for example be used for the appropriate adjustment of the tension of the strings of a sports racket (tennis, badmington, etc.), or else to measure the tension of a metal cable supporting any structure and prevent possible break. More generally, the cell can be used in any application where it is necessary to detect the movements of an object such as a wire or a cord, or else to measure the tension of a wire or a cord.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Multimedia (AREA)
• General Physics & Mathematics (AREA)
• Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
• Optical Measuring Cells (AREA)
• Electrophonic Musical Instruments (AREA)

Applications Claiming Priority (2)

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• 2003
  • 2003-05-02 FR FR0305387A patent/FR2854458B1/fr not_active Expired - Fee Related
• 2004
  • 2004-04-30 US US10/555,299 patent/US20060207413A1/en not_active Abandoned
  • 2004-04-30 EP EP04742617A patent/EP1629260A2/de not_active Withdrawn
  • 2004-04-30 WO PCT/FR2004/001051 patent/WO2004099739A2/fr active Application Filing

Non-Patent Citations (1)

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