EP2372695A1 - Method and device for determining the frequency of a string vibrating in a magnetic field - Google Patents

Abstract

The method involves generating a magnetic field by one or multiple electromagnetic pick-ups. The induction voltage or an induction current caused by the induction voltage caused by the change of the magnetic flux in the link is detected. The temporal run of the induction voltage or an induction current is evaluated. The frequency is evaluated as frequency of the link pulsatory in the magnetic field. Independent claims are also included for the following: (1) a device for determining the frequency of a string of a stringed instrument; and (2) a method for automatic tuning of a string of a stringed instrument.

Description

The present invention relates to a method and a device for determining the frequency of a string of a stringed instrument that oscillates in a magnetic field and contains or contains an electrically conductive material. The invention further relates to an apparatus and a method for automatically tuning a string of a stringed instrument, in which an as above-mentioned apparatus or a method for determining the frequency of the string is used.

It is known to determine the frequency of vibrating strings of stringed instruments, in particular in order to derive an actual tuning of the string and to allow a mood in the direction of a target mood. Such a mood can be done by hand, but especially by means of an automatic tuning device.

Usually, for the determination of the frequency of the vibrating string for purposes of tuning used as a structure-borne noise sensors, eg piezoelectric elements. These record the frequency of the vibrating string or one from these generated sounds. Such a solution is for example in the WO 2006/097126 A1 disclosed.

Furthermore, it is known to convert the sound produced by Elelctraguitarren by means of efektromagnetischer pickups into electrical signals, amplify them and finally make it audible through speakers. For this purpose, the metallic or Metellummantelten strings of Elelctrogitarre be placed immediately above a permanent magnet, so that they are exposed to a magnetic flux. Around the permanent magnet is arranged one or more coils in which, due to the changes in the magnetic flux caused by a swinging of the strings, an induction voltage is caused or an induced current caused by this voltage flows. This represents the electroacoustic signal of the electric guitar.

Even if a frequency of the oscillating string could basically be determined from this signal, this has not yet been undertaken, especially since crosstalk of adjacent vibrating strings makes it impossible or very difficult to assign a frequency to a specific string. Because often a separate permanent magnet is arranged below each of the individual strings, but placed around this arrangement of permanent magnets only a single coil. With this, the entirety of the acoustic signal caused by the vibrating strings is then sampled, without there being an assignment of the individual strings according to the respective frequency generated by you or the signal contribution. In addition, in conventional electric guitars, the electromagnetic pickups (also called pickup) are arranged in the region of the body of the guitar. This results in the need to transmit a signal from the body to the head in particular in those applications in which an automatic tuning of such a guitar by means of tension of the string ends to be made on the head. Such a need could be eliminated if all components could be arranged on the head of the instrument, in particular, the determination of the frequency of the vibrating string could take place there.

It is therefore an object of the invention to provide a method and apparatus for determining the frequency of a vibrating in a magnetic field, consisting of an electrically conductive material or containing a string of a stringed instrument, which is flexible and with low material and cost one for a mood the string allows sufficiently accurate determination of their frequency when swinging.

This object is achieved by a method which has the features of claim 1. With regard to a device, the solution of this problem is given in such a with the features of claim 7.

In the claims 10 and 13, finally, an improved device for automatic tuning of an existing or containing an electrically conductive material string of a stringed instrument and a related method are given.

In the dependent claims 2 to 6, 8 to 9 and 1 to 12 advantageous developments of the method for determining the frequency of the vibrating string, the related device and the device for automatic tuning of a stringed instrument are specified.

The special feature of the method according to the invention is that an induced due to the change in the magnetic flux in the string, which results from their oscillations in the magnetic field induced induction voltage or caused by this induction voltage induction current and their or its time course with respect Frequency evaluated and this frequency is evaluated as the frequency of the vibrating string in the magnetic field. If the string is at rest in a constant magnetic field, no induction voltage occurs; no induction current flows. If the string is now struck and excited to a vibration, it can occur in a non-homogeneous magnetic field, on the one hand, a change in field strength depending on the location where the string is currently on the other hand (even in a homogeneous magnetic field) to a Change in the surface penetrated by the magnetic field, resulting in a total change of the magnetic flux φ. This change in the magnetic flux causes an induction voltage U _ind according to the law of induction with U _lnd = - dφ / dt.

In other words, the voltage is proportional to the change in the magnetic flux which, due to the above considerations, occurs periodically, namely with the period, ie frequency, of the oscillating string. This results in the string itself between a different points of the string or between the string and an external mass tapped induction voltage, which in its time course also has the frequency of the vibrating string. This voltage can now be evaluated (or it is caused due to this voltage an induction current, which is evaluated) in terms of frequency, this frequency then represents the frequency at which the string oscillates.

Such determination of the frequency of the vibrating string can be carried out easily, in a confined space and with inexpensive means available. The method is basically feasible with all stringed instruments having electrically conductive strings, e.g. on pianos or guitars, especially electric guitars (electric guitars). The magnetic field, which is preferably static and need not necessarily be homogeneous or inhomogeneous for the application, may be e.g. be the earth's magnetic field. It is also possible that a magnetic field caused by a current flow through an adjacent string to the oscillating string whose frequency is to be determined is used as the magnetic field. If the stringed instrument, e.g. an electric guitar, an elecctromagnetic pickup, the magnetic field with particular advantage may also be that which originates from one or more contained in the electromagnetic Tonaufnehmer permanent magnet.

Since the induction voltage produced in the oscillating string or the induced current derived therefrom will generally have comparatively small values, it is advantageous to amplify this signal with regard to the frequency before an evaluation. For this purpose, known amplifier elements, for example Operational amplifier with low input resistance (eg in the range of 10 ohms) are used.

In addition to a computer and evaluation unit for determining the frequency, a device according to the invention has at least one voltage or current sensor connected thereto, as described above, for detecting the induced voltage in the string or an induced current derived therefrom. In principle, the sensor for receiving the induction voltage or an induction current derived therefrom along the length of the string can be contacted with the string at two offset points in order to determine the voltage arising therebetween or to detect an induced current derived therefrom.

In particular, if more than one string is connected to a corresponding sensor in order to be able to determine the frequency of their respective vibration for the different strings, however, a particularly compact design results if each of the sensors only contacts the associated string at one point and a second electrical contact or pole is formed on a ground opposite to which both or in the case of more than two sensors all sensors determine the voltage or the current.

In particular, the sensors can each mutually evaluate the potential of that string whose frequency is not measured as a mass. In the case where a plurality of strings are connected to corresponding sensors, an average of the potentials of the remaining strings can be assumed for the determination of the ground potential in the measurement of a vibrating string.

The invention also discloses a novel device for automatic tuning of a stringed or consisting of an electrically conductive material string of a stringed instrument. This contains as well as known devices for automatic tuning, eg those in the EP 1 596 359 A1 also described a control, a device connected to this device for determining the frequency of the string and an attacking on the string of The control can be specified motor-driven voltage adjustment. This automatic tuning device (tuning device) is characterized in that the device for determining the frequency of the string is one as described above. In this way, the above-described advantages of the novel device for determining the frequency of the vibrating string can be integrated into a tuning device.

In particular, it is advantageous that the device for determining the frequency of the string, as described above, can be made small and compact, that it is particularly suitable to be arranged at a common end of all the strings of the stringed instrument, in particular with the other components of the tuning device. In this way it is no longer necessary, as for example in the case of the EP 1 596 359 A1 known device to transfer signals for the transmission of the mood or the power supply from one end of the strings to the opposite end of the strings and to provide appropriate measures. Rather, it is sufficient to arrange the entire tuning device including the device for determining the frequency of the vibrating strings at one end of the latter, where then the entire process can take place in a confined space and with low-cost components and elements.

This tuning device is particularly suitable for arranging stringed instruments with a body, a neck and a head, in particular plucking instruments such as guitars, banjo, mandolin, e-bass or the like, or stringed instruments such as violins, violas, cello, double bass or the like.

Fig. 1

schematisch eine Verschaltung zur Aufnahme der in einer in einem Magnetfeld schwingenden Seite induzierten Spannung und Verstärkung derselben zur Ausgabe in eine Frequenzanalyseeinrichtung;

Fig. 2

schematisch die Darstellung einer E-Gitarre, in welcher das erfindungs-gemäße Prinzip zur Bestimmung der Frequenz einer schwingenden Saite Anwendung finden kann.

Further advantages and features of the invention will become apparent from the following description of an embodiment with reference to the accompanying figures. Showing:

Fig. 1

schematically an interconnection for receiving the voltage induced in a magnetic field oscillating side and amplifying the same for output in a frequency analysis device;

Fig. 2

schematically the representation of an electric guitar, in which the inventive principle for determining the frequency of a vibrating string can apply.

In Fig. 1 is shown in a schematic diagram of the principle for detecting the voltage induced in or consisting of an electrically conductive material containing a string when it moves periodically oscillating in a magnetic field. Shown here is a portion of a string 1, shown here in a rippled representation with undulating rashes to illustrate the periodically oscillating motion. Shown further is illustrated by arrows, the magnetic field B, in which the string 1 and the section of the string is located.

At two contact points 2, 3, the string 1 is electrically contacted. Via electrical lines 4, 5, the contact points 2, 3 are connected to the inputs of an operational amplifier 6. The amplified signal is fed from the operational amplifier 6 to an output line 7.

In operation, when the string 1 vibrates, the magnetic flux φ changes between the contact points 2, 3 due to the string 1 formed as an electrical conductor, so that there an induction voltage U _{ind is produced} according to the law of induction U _ind = - dφ / dt. This induction voltage U _ind is applied via the electrical lines 4, 5 to the inputs of the operational amplifier 6, an amplified signal (current signal or voltage signal) is applied to the output line 7.

The output line 7 is connected to a computer and evaluation not shown here. There, the output signal on the output line 7 is analyzed for a frequency of its periodic variations.

Now, if the string 1 vibrates or oscillates with a specific natural frequency given by its mood, the magnetic flux φ flowing through the string 1 in the constant magnetic field B also varies at the same frequency, so that, due to the law of induction, a with just the frequency with which the string oscillates, periodically varying induction voltage U _ind results. The frequency is not changed by the amplification process in the operational amplifier, so it is also the signal applied to the output line 7 own. The frequency can now be determined in the computer and evaluation device by means of known frequency analysis methods, such as Fourier transformation, fast Fourier transformation (FFT) or the like. The result of this frequency determination can now in turn be supplied as the actual value of a device for automatic tuning of the musical instrument by comparing this actual value with a desired value and changing the voltage of the vibrating string 1 to the actual value ultimately to the Adjust target value.

In Fig. 2 schematically shows a guitar 10 as an example of a stringed instrument, in which the inventive method for determining the frequency of the vibrating string and also the device according to the invention, optionally in combination with an automatic tuning device, can be used. The guitar 10 is divided in a known manner in a body 11, a neck or web 12 and a head 13. Between a bridge 14 on the body 11 of the guitar 10 and arranged on the head 13 vertebra 15 extends in the longitudinal direction of the neck 12, the string 1. In this illustration, only one string 1 is drawn, but the guitar 10 typically has more strings, in this embodiment, six parallel strings, each and with a lateral distance from the bridge 14 to a vortex 15 on the head 13th the guitar 10 extend.

The guitar string 1 is made of metal or is coated with metal, so that it is electrically conductive.

On the body 11 of the guitar 10 are below the string 1 two electromagnetic pickups (pickups) 16 and 17 are arranged. These electromagnetic pickups 16, 17, which are shown here only very schematically, contain permanent magnets, which are arranged with one of their poles close below the respective associated string 1, but without touching them. Thus, the string 1 in the field of electromagnetic pickups 16, 17 permanently from a flows through magnetic flux φ. This changes, as stated above, when the string is excited to vibrate. Due to this change, an induction voltage U _{ind is} caused in the metallic conductive string, which can be tapped as described above. When the guitar, as in Fig. 2 is shown, this is preferably done by only one contact point on the string is tapped, which may be connected to the metallic conductive vortex 15, for example. To determine the voltage, a ground potential is provided to the amplifier as the opposite pole, which can either be a system ground of a downstream electrical or electronic circuit, or an averaged potential of the other five, not shown here and at the moment of the measurement recording in terms of their vibration frequency to be determined strings.

LIST OF REFERENCE NUMBERS

1

string

2

contact point

3

contact point

4

electrical line

5

electrical line

6

operational amplifiers

7

output line

10

guitar

11

corpus

12

Neck, bridge

13

head

14

bridge

15

whirl

16

electromagnetic pickup

17

electromagnetic pickup

B

magnetic field

_Und

induction voltage

Claims (13)

A method for determining the frequency of a string of a stringed instrument that oscillates in a magnetic field or consists of an electrically conductive material, whereby the induction voltage caused by the change in the magnetic flux in the string or an induced current caused by the same is detected and its or their evaluated time course with respect to the frequency and this frequency is evaluated as the frequency of the vibrating string in the magnetic field. A method according to claim 1, characterized in that the magnetic field generated by one or more electromagnetic pickups is used as the magnetic field. A method according to claim 1, characterized in that a magnetic field generated by a to the oscillating string whose frequency is to be determined, adjacent from an electrically conductive material or containing a string, which is traversed by an electric current, magnetic field is used , A method according to claim 1, characterized in that the magnetic field of the earth is used. Method according to one of the preceding claims, characterized in that the magnetic field is a constant magnetic field. Method according to one of claims 1 or 2, characterized in that the induction voltage or the induction current is amplified before an evaluation of its or its time course. Device for determining the frequency of a string (1) of a string instrument comprising several such strings (1) oscillating in a magnetic field (B) and comprising at least one string (11) whose frequency is oscillating to be connected, connected voltage or current sensor for determining an induction voltage (U _lnd ) built up in the string (1) or with an induced current induced thereby and with a computer and evaluation unit connected to the voltage or current sensor for determining a frequency with which the induction voltage (U _ind ) resp. the induction current changes periodically over time. Device according to claim 7, characterized in that there are at least two voltage or current sensors connected to one associated string (1), the voltage sensors having only one electrical connection to each of the strings (1) and the computer and evaluation unit or the sensors are set up in such a way that they accept the connection to the string (1) whose frequency is not currently determined as the mass against which the induction voltage (U _ind ) or the induction current is measured. Apparatus according to claim 7, characterized in that all strings (1) have an associated voltage or current sensor and that all voltage or current sensors are connected with only one electrical line to the associated string (1), wherein the computer and evaluation unit or the sensors are set up in such a way that they assume an average of the potential of all the connections to the strings (1) whose frequency is not currently determined, as mass against which the induction voltage (U _ind ) or the induction current is measured. Device for automatically tuning a string (1) of a stringed instrument (10) consisting of or containing an electrically conductive material, comprising a controller, a device connected to it for determining the frequency of the string (1) and one on the string (1) engaging, controllable by the control motor-driven Spannungsverstelleinrichtung, characterized in that the device for determining the frequency of the string (1) is such according to one of claims 7 to 9. Apparatus according to claim 10, characterized in that all its components are arranged in an area in which all the strings (1) are fixed with one of their longitudinal ends. Apparatus according to claim 11, characterized in that the stringed instrument (10) comprises a guitar, a banjo, a mandolin or a comparable plucking instrument or a violin, a viola, a cello, a double bass or a similar comprising a body, a neck and a head a string, a neck and a head having bowed instrument and that all components of the device for tuning the string (1) on the head (13) of the stringed instrument (10) are arranged. A method of automatically tuning a stringed string string comprising or containing an electrically conductive material comprising the steps of determining the current frequency of the vibrating string, comparing that current frequency with a desired frequency, and automatically obtaining the desired frequency adapted adjustment of the tension of the string to be tuned, characterized in that the frequency of the vibrating string is determined by a method according to one of claims 1 to 6.

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