JPH0480397B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stringed musical instrument device. More specifically, the present invention separately detects the vibrational motion of the strings of a stringed musical instrument device in two mutually perpendicular planes;
and a new and improved transducer for obtaining separate electrical signals relating to the vibratory motion of a string in each of two mutually perpendicular planes.

BACKGROUND OF THE INVENTION Transducers, or commonly referred to as pick-ups, are widely used in various types of electronic guitars and other string instrument devices to obtain electrical signals corresponding to the vibrating motion of strings. ing.
This electrical signal is amplified and fed into a speaker, producing a sound that is louder than the sound produced by the vibrations of the strings themselves. Most people who vibrate guitars or similar stringed instruments use transducer-based devices.

Typical prior art transducers use iron core pole pieces of magnetic material. This core allows magnetic field lines to pass through and radiates magnetic field lines. The core is placed in close proximity to the string, and as the string vibrates toward and away from the core, the reluctance across the air gap in the immediate vicinity of the core changes. A change in reluctance causes an associated change in the magnetic flux within the core, and this flux change induces an electrical signal. Conventional transducer assemblies typically detected the vibratory motion of the strings in a plane perpendicular to the plane collectively defined by all the strings of the device.

It has been found that when a string is plucked, the string typically vibrates in a complex pattern. When you pluck a string, the center point of the string vibrates in a linear, circular, elliptical, figure-eight, or other complex pattern. However, prior art transducers only detected string motion in a single plane. However, the actual audio effect produced by the vibrating string itself includes many frequencies and effects that are distinguishable from the vibrating motion of the string in a single plane. Therefore, the electrical signals obtained by prior art single sensing planar transducers do not accurately reflect the acoustic effects produced by the vibrating string.

Some prior art transducers have even attempted to eliminate the effects of string vibrations in planes other than the single sensing plane. U.S. Pat. No. 3,453,920 describes a piezoelectric bridge pick up for a guitar. Two piezoelectric crystals are placed in mechanical contact with the strings in a bridge shape to detect the vibrations of the strings. The piezoelectric crystal is oriented in a fixed direction and detects the horizontal and vertical vibrations of the string. However, this crystal also dampens string motion. The piezoelectric crystal is electrically connected to electrically cancel the signals resulting from horizontal vibrations of the string.

Prior art relating to obtaining signals representative of string vibrations in two mutually perpendicular planes is disclosed in U.S. Pat.
Described in No. 4143575. US Patent No. 4143575
The apparatus described in the No. 2003-11-11 is comprised of a pair of radio-frequency coils with axes that do not intersect each string, a signal generator for transmitting a radio-frequency signal through each string of a string instrument, and a radio-frequency coil. A signal processing circuit equipped with an AM detector for detecting modulation in the detected time-series radio frequency signal, and an amplifier and a speaker for amplifying the audio signal obtained from the AM detector are used.
Conventionally, radio frequency signal processing equipment and radio frequency coils are arranged in mutually perpendicular planes with sufficient signal separation to obtain two distinguishable audio signals from string vibrations in two mutually perpendicular planes. It was thought necessary to detect the vibrations of the string in each of the two planes.

It shows the lack and lag in development in this field.
However, the overall significance of the present invention will be better understood if one is fully aware of the state of prior development in this field.

OBJECTS, SUMMARY AND EFFECTS OF THE INVENTION The general object of the present invention is to provide a new and improved variable reluctance and variable flux transducer for sensing the vibrational motion of a string in two mutually perpendicular planes. It is to obtain. This transducer has the important advantage and feature of more completely reproducing the complex motion of a vibrating string. This feature allows a skilled player to obtain two distinct sound effects from one vibrating string, and increases the salience of the player's playing style. The transducer can be used with conventional audio amplification equipment without the need for expensive and complex signal processing equipment. This transducer can also be used with various signal processing devices to obtain unique musical effects. Another object of the present invention is to easily increase the number and salience of tones available from a string instrument using an electrical transducer for detecting string vibrations.

The transducer of the present invention comprises at least one pair of core pole pieces, a device for generating mutually equal magnetic flux passing through each of the cores, and a device for detecting changes in the magnetic flux; It can be summarized as a whole. A magnetic pole face of a predetermined shape is created on each core. This predetermined shape of the pole face radiates a predetermined pattern of magnetic flux lines from the iron core into the air gap near the string. When the string vibrates in one plane parallel to the magnetic flux line pattern radiated from the magnetic pole face of the first iron core,
The magnetic flux changes within the second core are minimal and negligible. The reverse is also true. That is, when the string vibrates parallel to the magnetic flux line pattern emerging from the magnetic pole face of the second iron core, the change in the magnetic flux within the first iron core is negligible. Thus, the vibrational motion of the string in one plane is
It is detected independently of the vibratory motion of the string in other mutually perpendicular planes and with minimal influence on the others. Further, the pair of iron cores are arranged on opposite sides in a direction transverse to the length direction of the string. This causes the same amount of magnetic flux from both cores to intersect each string at the same point. With such a configuration, it is possible to generate two signals that are clearly and sufficiently separated from each other from string vibrations in two vibration planes.

[Embodiments and Effects] The present invention relates to a device used by being attached to a stringed musical instrument device such as a guitar having a plurality of strings 12 shown in FIG. The present invention is the second
1. One or more transducers 14 are shown in FIGS. 3 and 4. The transducer of the present invention detects the vibratory motion of the string 12 in two substantially mutually perpendicular planes, and provides separate signals representative of the vibratory motion of the string in each of the two mutually perpendicular planes. will occur. Prior art transducers or pick-ups are typically used to detect the vibrational motion of a string in virtually only one plane.

When the string 12 is plucked, the string typically vibrates in a very complex pattern and does not vibrate in just one plane. Complex vibration patterns occur because the strings are not plucked uniformly, or because the angles at which the plucked nails strike the strings vary. In any case of a complex vibration pattern, the components of vibration or motion in two mutually perpendicular planes parallel to the non-vibrating string, shown in the x and y planes of Figure 2. will have. In fact, if a string moves, it will have components of motion in two planes, except in one plane parallel to either the x-plane or the y-plane. The transducer 14 of the present invention separately detects the vibration motion components of the string in two mutually perpendicular planes, the x-plane and the y-plane,
Separate electrical signals are then generated representing the vibratory motion of the string in each plane.

Transducer 14 is typically incorporated into a transducer assembly 16 and attached to a guitar or string instrument, as shown in FIGS. 1 and 6. The transducer assembly 16 is preferably positioned below the plane defined by the plurality of strings 12 and attached to the body 18 of the guitar 10. String 1
2 is stretched between two bridges 20 and 22 of the guitar, and the transducer assembly 16 is positioned between the two bridges. Bridges 22 and 23 define the maximum length in the longitudinal direction over which string 12 can vibrate, since the bridges dampen the vibrations of the string relative to the guitar body. A transducer 16 is placed somewhere on the suspended portion of the string that undergoes a vibratory motion, such as when the string is plucked or struck.

Electrical signals representative of the motion or vibration of the string in each of two mutually perpendicular planes are separately fed directly to audio amplifiers 24 and 25, as shown in FIG. drives speakers 26 and 27. The signal supplied to amplifier 24 represents the vibrational motion of the string in one of the two mutually perpendicular planes, and the signal supplied to amplifier 25 represents the vibrational motion of the string in one of the two mutually perpendicular planes. represents the vibrational motion in the plane of Terminals 28 and 30 attached to the guitar are connected to transducer assembly 1.
6 to the amplifiers 24 and 25. As shown in Figure 2,
Separate terminal pairs 28a and 30a are provided for each transducer 14 of assembly 16, thereby providing a separate pair of signals from each string. Or, as shown in FIG. 7, the various electrical signals can be summed at one terminal 28 and 30.

The principle of operation of transducer 14 is illustrated schematically in FIG. Each transducer has a first core pole piece 32 and a second core pole piece 34. Because each core is made of magnetic material and placed in close proximity, each core has a certain magnetic reluctance. Iron cores 32 and 34
Apparatus is also provided for producing magnetic flux entering and exiting. In the transducer 14 shown in FIG. 2, cores 32 and 34 are permanent magnets whose magnetic material produces magnetic flux. Each of the cores 32 and 34 has a predetermined shaped pole face 36 and 38, respectively, to radiate a predetermined pattern of magnetic flux out of the core.
The magnetic flux radiated from the pole faces 36 and 38 into the spatial region or gap region near the string 12 has a predetermined pattern aligned substantially parallel to the two planes x and y, respectively. ing.

One predetermined shape for the pole faces 36 and 38 is a planar pole face, which allows the magnetic flux patterns to be arranged perpendicularly to each other in the vicinity of the strings. When magnetic flux exits the iron core, it tends to exit virtually perpendicular to the magnetic pole face. When magnetic flux leaves the magnetic pole face and travels through space, the lines of magnetic flux tend to bend due to other influences. By using other shapes of pole faces that are not flat, it is possible to arrange the magnetic flux lines to cross each other perpendicularly in the region near the non-vibrating strings.

Iron cores 32 and 34 and their respective pole faces 36 and 38 are positioned and held in a predetermined positional relationship with respect to string 12. As a result of these being maintained in a predetermined positional relationship, the magnetic flux radiated from the iron core 32 through its magnetic pole face 36 intersects the string 12 in a state parallel to the x-plane as a whole. Magnetic flux radiated from core 34 through its pole face 38 intersects chord 12 generally parallel to the y-plane and substantially perpendicular to the x-plane.

The strings 12 of a typical musical instrument are generally made of a magnetizable material such as steel. However, in the case of a string made of a non-magnetizable material, it is possible to make it magnetizable by placing a small foil made of a magnetizable material around the string near where the magnetic flux from the iron core intersects the string. I can do it. Since the string 12 is located at a predetermined distance from the pole faces 36 and 38 and is within the magnetic flux pattern radiated from the iron core, the oscillatory motion of the string in the x and y planes causes the magnetic flux to The magnetic reluctance of the tract is affected. When the string 12 vibrates toward and away from the magnetic pole face 36, the reluctance of the magnetic path passing through the iron core 32 changes depending on the distance from the magnetic pole face 36 to the string 12. Since the distance from the magnetic pole face 36 to the string changes the same as the frequency of the string in the x-plane,
Changes in reluctance directly represent the string's frequency.
A similar effect changes the reluctance of the magnetic path through the iron core 34 when the string makes an oscillating motion toward and away from the pole face 38 in the y-plane.

When the reluctance of each magnetic path changes,
The magnitude of the magnetic flux passing through the iron core in the magnetic path changes accordingly. Coils 40 and 42 are wound around cores 32 and 34, respectively, to convert changes in magnetic flux within each core into electrical signals. These electric coils 40 and 4
2 is defined as a series connection of a plurality of individual loops of conductors 44 and 46, respectively, or a coil of these conductors. As the magnetic flux through the core changes, voltage signals are induced in sensing coils 40 and 42, and these signals are applied to conductors 44 and 4.
6 to a pair of terminals 28a and 30a connected to conductors 44 and 46, respectively.

The iron core and the magnetic pole faces each intersect the string 12 while maintaining the relationship that the lines of magnetic force coming out from each magnetic pole face 36 and 38 are perpendicular to each other, so when the string moves in one plane, the lines of force in the other plane intersect with each other. The magnetic flux of the iron core, which radiates magnetic field lines parallel to , does not change. For example, if the string moves in the x-plane, no change in the magnetic flux within the core 34 occurs. This is because string 12 is virtually always equidistant from pole face 38. The same is true for other cores when the string moves in the y-plane. Although a slight bending and some interaction of the magnetic field lines radiated from the pole faces 36 and 38 may occur in the vicinity of the string 12, a disturbance in the proper vertical orientation in the vicinity of the string may occur. It is not large enough to prevent separation of changes in magnetic flux within cores 32 and 34 due to changes in reluctance caused by the respective vibratory motions of the strings in the x and y planes.

The shape of the core, the pole faces, and the predetermined magnetic flux line pattern in the vicinity of the string, according to the present invention, have the greatest influence on the magnetic flux in one core when the string vibrates in one plane. but are selected to have minimal or no effect on the magnetic flux in other cores, so that two mutually perpendicular
Separate electrical signals are obtained from each movement of the string in two planes. The predetermined distance from the magnetic pole face to the string, the amount of magnetic flux passing through and generated within each core, and the number of turns of each detection coil are all related in a predetermined manner. The voltage output signals available at 28a and 30a are transmitted to the audio amplifier 24 or 26 (the first
(Figure) can be used to drive directly.

Skilled musicians can use the transducer of the present invention to create unique musical styles and musical effects that were previously unrecognizable. Significant acoustic differences result from the respective vibrations of the string in two mutually perpendicular planes. The overall sound produced by the transducer of the present invention is subjectively larger in scale and richer than the sound produced by conventional transducers. Since a different signal is obtained for each detection coil, a stereo image can be obtained. This stereo image changes depending on how the instrument is played. If a string is plucked laterally between two iron cores, the initial lateral linear vibrations of the string will induce alternating primary signals in the iron cores. By plucking the strings back and forth, two separate speakers 26 and 27 (first
The image of the sound will move back and forth across the stereo space defined by the interval between the two. By appropriately plucking the string, the musician can also bend or displace the string toward one pole face and away from another pole face. As the string bends closer to one pole face, the amplitude of the signal in one sensing coil increases and the amplitude of the signal in the other sensing coil decreases, so that the amplitude of the audio image is equal to that of the two loudspeakers. The stereo will move to one side between the two. It is also possible for experienced performers to obtain sophisticated flanging or fading effects. This fading or flanging effect is controlled by plucking the string at successive intervals along the length of the string, thereby causing the vibrations to change one after the other and creating multiple patterns in the vibrating string. Retained. The speed at which fading occurs is determined by the speed at which the plucking motion moves along the length of the string. These unique effects and other unique effects are simultaneously but independently controlled by the performer.

The unique musical effects provided by the transducer of the present invention are a direct result of its vibration detection capabilities. Other than using conventional audio amplifiers 24 and 25 and conventional speakers 26 and 27, there is no need for cumbersome additional electronic equipment such as signal processing equipment. The transducer of the present invention can be installed directly into a conventional guitar or other stringed instrument device, or can be used in place of a conventional pick-up without major modifications to a musician's equipment or audio amplification equipment. It can be used instead.

A preferred construction of one practical embodiment of a transducer is shown in FIG. Preferably, cores 32 and 34 are made of long rods of magnetic material. The coil frame 48 is generally reel or bobbin shaped and has a central opening 50 through which the core passes. Coil frame 48 between end flanges 52 and 54 of each coil frame
Detection coils 40 and 42 are created by winding a predetermined number of turns of conductive wire around the middle portion of the coils. A permanent magnet 56 contacts ends 58 and 60 of cores 32 and 34, respectively. Permanent magnets 56 create a magnetic flux that passes through cores 32 and 34. Metal magnetic shield 62 (Fig. 5)
is located between end flanges 52 and 54 and completely surrounds each of sensing coils 40 and 42. The shield 62 is made of a single plate of metal material in the shape of a figure 8, as shown in FIG. 5, and can slide over both the detection coil and the coil frame simultaneously. . Staggered ends 64 overlap the central portion of the metal shield to complete the magnetic shielding around each sensing coil. Shield 6
2 serves to shield the detection coils 40 and 42 from the influence of external spurious magnetic flux lines and reduce the induction of spurious electrical signals in the detection coils. The transducer 14a is assembled and the guitar body 18
and the core and pole faces are positioned relative to the string 12 by a retainer or container 66. The holding device or container has an upper wall 68 and a lower wall 70. There is an opening 71 in the upper wall 68 through which the ends of the cores 32 and 34 project and are held near and transversely to the string.

Embodiment 1 of the transducer shown in FIG.
4a, pole faces 36 and 38 are created by cutting planes on cores 32 and 34, respectively, at an angle of approximately 45° to the length of the core. The magnetic pole faces 36 and 38 are both string 1
2, and when the string is in a non-vibrating state, the distance from the string 12 to each pole face is approximately the same. Imaginary lines 72 extending perpendicularly from planar pole faces 36 and 38, respectively, represent chords 12
Intersect at. The magnetic field lines emanating from the pole faces 36 and 38 generally intersect the string 12 in a mutually substantially perpendicular relationship due to said geometry. Of course, the planes defined by pole faces 36 and 38 are also perpendicular to each other.

Embodiment 1 of the transducer shown in FIG.
4b, the ends 74 and 76 of the core 32 are connected to the container 6.
6 protrudes above the upper surface 68 of the string 12 and curves towards convergence towards the string 12. The shape of the pole faces 36 and 38 is planar. Pole faces 36 and 38 are laterally flared and generally extend toward end 7.
4 and 76. Pole face 36 in embodiment 14b shown in FIG.
The directions 38 and 38 have substantially the same pole face arrangement as described above, and produce substantially the same magnetic field line pattern as described above in the vicinity of the string.

A plurality of individual transducers, such as 14a, are assembled to form a transducer assembly 16, as shown in FIG.
One of the individual transducers in this assembly 16
One is attached to each string 12 of the stringed instrument. Each individual transducer provides a signal representative of the vibratory motion of the string to which it is attached. Transducer assembly 1
6 container 66 to guitar body 18, screws 80 or other conventional fastening devices are used. It is noted that the pole faces 36 and 38 of the assembly 16 are arranged along a line transverse to the length of the string and are located in close proximity to the string whose vibrations are to be detected. Cut it off. Each transducer detects the vibratory motion of the string at approximately corresponding locations along the length of the string involved.

The detection coils of each transducer of a transducer assembly may be electrically connected in a variety of different ways. One of these methods is shown in FIG. The sensing coils 40 of the two cores 32 on the same lateral side of the string 12 are connected to the resistors 82 and 8.
4 and is electrically connected to the terminal 30. This terminal also serves as a summing junction. The resistance values of resistors 82 and 84 are selected so that the magnitude of the individual signal obtained from each of the sensing coils 40 is the required magnitude. In the same way,
The detection coil 42 around the iron core 34 is connected to a resistor 86.
and 88 are electrically connected to the terminal 28 . In the electrical circuit shown in FIG. 7, a first set of electrical signals, i.e., the set of electrical signals resulting from the oscillatory motion of all or more strings in a set of parallel planes, are all summed, and A second set of electrical signals, ie the remaining set of electrical signals resulting from the vibratory motion of the string in a set of mutually perpendicular planes, is added. Although not shown, the signals obtained by each individual detection coil may be fed separately to separate amplifiers, or one of the conventional techniques may be used to obtain destructive interference, such as "humbucking" ( It is also possible to connect by humbucking.

A preferred embodiment of the transducer of the present invention, its principle of operation and significant improvements and advantages over the prior art have been described in detail. However,
It is to be understood that the description herein is illustrative and that changes may be made in structural details without departing from the scope of the invention.

[Brief explanation of the drawing]

FIG. 1 is an overall view of a guitar equipped with a transducer assembly including at least one transducer according to the present invention. Electrical output terminals and various other electrical devices for the transducer assembly are also shown schematically. FIG. 2 is an overall schematic diagram of a transducer according to the invention, illustrating the elements and principles of the transducer, mounted on one string of a guitar or other stringed instrument. FIG. 3 is a side view of one embodiment of the transducer of the present invention in a plane perpendicular to the length of the string of a stringed instrument, with a portion shown in cross-section. FIG. 4 is a diagram similar to FIG. 3 regarding another embodiment of the transducer of the present invention. Fifth
The figure is a sectional view taken along line 5--5 in FIG. 3 or 4. FIG. 6 is a three-dimensional view of one transducer assembly having multiple individual transducers positioned for each string of the guitar shown in FIG. 1; FIG. 7 is an exemplary electrical schematic of one of the two transducers of the transducer assembly. 32...First magnetic material core, 34...Second magnetic material core, 56...Magnetic flux generator, 36...First
Magnetic pole surface, 38...Second magnetic pole surface, 66, 68, 7
0,80...Holding device, 40...First coil, 4
2...First coil.

Claims (1)

[Claims] 1. A transducer for a stringed musical instrument having at least one magnetically permeable string, the transducer comprising an electrical transducer for each vibrational motion of the string in two intersecting planes at an angle. The transducer, which is of the variable reactance type for obtaining a signal, comprises: at least one pair of first and second magnetically permeable pole pieces; and means for generating equal magnetic flux in each of the pole pieces. , first and second pole faces formed on the first and second pole pieces, each radiating an equal magnetic flux from each pole piece; and connecting the first and second pole pieces to the string. a retaining device for retaining and locating on opposite sides transverse to the length; and a first pole piece associated with a change in magnetic flux within the first pole piece.
a device associated with the first pole piece for providing an electrical signal; and a second device associated with changing magnetic flux within the second pole piece.
a device associated with the second pole piece for providing an electrical signal, the holding device positioning the pole face in a predetermined fixed position relative to the string in a non-vibrating state; The retaining device also positions the first pole face at a predetermined distance from the string;
Therein, a magnetic flux change is significantly greater in the first pole piece than any flux change in the second pole piece when the string vibrates in a first plane toward and away from the first pole face. , and the holding device also positions the second pole face at a predetermined distance from the string, where the string is in a second plane in directions toward and away from the second pole face. The retaining device causes a magnetic flux change in the second pole piece that is significantly greater than any magnetic flux change in the first pole piece when in an oscillatory motion, and the retaining device
A transducer characterized in that both said magnetic pole faces are positioned at predetermined positions such that their in-plane vibratory motion substantially intersects the vibratory motion of said string in said second plane. 2. The transducer of claim 1, wherein the retaining device is further configured such that the vibratory motion of the string in the first plane is mutually perpendicular to the vibratory motion of the string in the second plane. A transducer characterized in that both said magnetic pole faces are arranged in a predetermined shape. 3. In the transducer according to claim 1, the lines of magnetic force radiated from the magnetic pole face are predetermined in a predetermined pattern within a predetermined distance from the magnetic pole face. each of the magnetic pole faces has a shape, and the holding device is configured such that the predetermined magnetic field line pattern radiated from the first magnetic pole face is a constant shape with the predetermined magnetic field line pattern radiated from the second magnetic pole face. A transducer characterized in that both said pole faces are arranged relative to said non-vibrating string in a predetermined manner such that they intersect at an angle. 4. In the transducer according to claim 3, the predetermined magnetic field line patterns respectively radiated from the first magnetic pole surface and the second magnetic pole surface interact with each other in the vicinity of the string in a non-vibrating state. A transducer characterized by substantially vertical intersections. 5. The transducer of claim 1, wherein at the predetermined position where each pole piece is held relative to the string, each pole face extends substantially from the pole piece to the string. one said pole face emits lines of magnetic field towards said string and the other said pole face emits lines of magnetic field towards said string. A transducer characterized by a magnetic pole surface that emits radiation at a constant angle with the radiated lines of magnetic force. 6. The transducer according to claim 5, wherein the direction of the lines of magnetic force radiated from one of the magnetic pole faces is substantially perpendicular to the direction of the lines of magnetic force radiated from the other pole face. transducer. 7. In the transducer according to claim 1 or 5, most of the lines of magnetic force radiated from the first magnetic pole surface and the second magnetic pole surface, respectively, are oriented in mutually perpendicular directions and directed toward the string. A transducer characterized by crossing. 8. In the transducer according to claim 1, 3, or 5, when the string vibrates toward and away from one of the pole faces, the magnetic flux within one of the pole pieces increases. A transducer characterized in that the predetermined shape of the pole face is selected such that the change in magnetic flux in other of the pole pieces is significantly greater than the change in magnetic flux in other of the pole pieces. 9. The transducer of claim 1, 3, or 5, wherein the retaining device holds each pole face substantially equidistant from the string when the string is in a non-vibrating state. A transducer characterized in that it is arranged as follows. 10 Claims 1, 3, or 5
3. The transducer of claim 1, wherein each of the pole faces is planar in shape, and the plane of the first pole face is substantially perpendicular to the plane of the second pole face. 11 Claims 1, 3 or 5
In the transducer of paragraph 1, each of said pole pieces is in the form of an elongated rod, said pole face extending across the end of said rod, and said rod extending near the end at which said pole face is formed. A transducer characterized by its curved shape. 12 Claims 1, 3 or 5
In the transducer of paragraph 1, each of the pole pieces is in the form of a long rod, and the pole face crosses the end of the rod at an acute angle to the length of the rod. A transducer characterized in that the transducer extends from the top to the right. 13 Claims 1, 3 or 5
In the transducer of paragraph 1, the first electrical signal and the second electrical signal are substantially exclusively audio frequency signals of predetermined strength applied directly to the input of an audio amplifier, and the first electrical signal and the second electrical signal are Second
Transducer characterized in that the signals are distinguishable from each other according to the different vibrational motions of the strings in each of the two said planes. 14 Claims 1, 3 or 5
In the transducer according to paragraph 1, the string instrument device has a body and a plurality of strings existing in one plane, one first pole piece and one second pole piece.
a pole piece is operatively associated with each of the plurality of strings of the device, the retaining device is operatively connected to the body and the pole face of the pole piece is in a plane defined by the plurality of strings; , and the retaining device also positions each first pole face on a corresponding transverse side to the length of each string and each second pole face to a corresponding transverse side to the length of each string. A transducer characterized by being placed on the lateral side of the vehicle. 15. The transducer of claim 14, wherein the retaining device holds the first pole piece and second pole piece of each group of first pole pieces and second pole pieces in one string associated with each group. adjacent to and 1
A transducer characterized in that one of the strings and the first and second pole pieces of the group are arranged without intervening other pole pieces. 16. The transducer of claim 14, wherein each said pole piece is in the form of an elongated bar, said pole face extending across an end of said bar, said bar having said pole face A transducer characterized by a bend near the end where it is made. 17. The transducer of claim 14, wherein each of said pole pieces is in the form of an elongated bar, and said pole face forms an acute angle with respect to the length of said bar at said end. A transducer characterized in that it extends across the end of the rod.