Noise reduction device

Abstract

A passive noise reduction device may be used with an instrument having at least one electromagnetic pickup. The device may include a device coil wound so as to form at least one free-shaped ring, a first terminal for connection to the pickup coil, and a second terminal for connection to ground. The device coil is responsive to the one or more stimuli so as to produce a noise electrical signal component in the device coil. The pickup coil and the device coil are in substantially the same plane. The noise reduction device coil is wound such that the pickup noise electrical signal component is substantially 180 out of phase with respect to the device noise electrical signal component, and such that the device noise electrical signal component destructively interferes with the pickup noise electrical signal component so as to reduce noise in a resultant electrical signal into the output circuit.

Claims

1. A passive noise reduction device for use with an instrument having one or more strings, the instrument including at least one electromagnetic pickup including at least one coil, the pickup responsive to vibration of at least one string so as to produce a music electrical signal component in the pickup coil and responsive to one or more stimuli in addition to the string vibration so as to produce a noise electrical signal component in the pickup coil, a first terminal of the pickup coil for connection to an output circuit, a second terminal of the pickup coil for connection to the device, the noise reduction device including: a device coil including a conductor, wherein the conductor is wound so as to form at least one free-shaped ring, a first terminal of the device coil for connection to the second terminal of the pickup coil, a second terminal of the device coil for connection to ground, the device coil responsive to the one or more stimuli so as to produce a noise electrical signal component in the device coil, wherein the conductor substantially accords with formula: $\frac{8L}{A}=R,$ where: is resistivity of the conductor, L is length of the conductor, A is cross-sectional area of the conductor, and R is resistance of the pickup coil, wherein the pickup coil and the device coil are in substantially the same plane, and wherein the noise reduction device coil is wound such that the pickup noise electrical signal component is substantially 180 out of phase with respect to the device noise electrical signal component, and such that the device noise electrical signal component destructively interferes with the pickup noise electrical signal component so as to reduce noise in a resultant electrical signal into the output circuit.

2. A passive noise reduction device according to claim 1, wherein the conductor is copper wire.

3. A passive noise reduction device according to claim 1, wherein the conductor is electrically insulated.

4. A passive noise reduction device according to claim 1, wherein A is approximately 8 10.sup.9 m.sup.2, is approximately 1.68 10.sup.8m, and L is approximately 345 m.

5. A passive noise reduction device according to claim 1, wherein the conductor is 34 American Wire Gauge (AWG) to 42 AWG wire.

6. A passive noise reduction device according to claim 1, wherein the conductor is 38 AWG or 39 AWG wire.

7. A passive noise reduction device according to claim 1, wherein the conductor is about 15 meters to about 400 meters long.

8. A passive noise reduction device according to claim 1, wherein the conductor has impedance of about 200 to 1000 .

9. A passive noise reduction device according to claim 1, wherein the conductor is wound onto a substrate.

10. A passive noise reduction device according to claim 9, wherein the substrate is an adhesive film or tape.

11. A passive noise reduction device according to claim 1, wherein the device coil is electrically insulated.

12. A passive noise reduction device according to claim 1, wherein the free-shaped ring has a diameter of approximately 8 cm to approximately 10 cm, when placed in a substantially circular shape.

13. A passive noise reduction device according to claim 1, wherein the free-shaped ring is wound to form a substantially flat cross-sectioned ring.

14. A passive noise reduction device according to claim 1, wherein the free-shaped ring has a cross-sectional width of approximately 1 cm.

15. A passive noise reduction device according to claim 1, wherein the device coil includes two or more free-shaped rings.

16. A passive noise reduction device according to claim 15, wherein the one of the free-shaped rings is formed to be 180 out of phase with respect to at least one other of the free-shaped rings for use with an instrument including two or more electromagnetic pickups, one of the electromagnetic pickups being wound 180 out of phase with respect to at least one other of the electromagnetic pickups, or for use with an instrument including at least one electromagnetic pickup having at least two pickup coils, one of the pickup coils being wound 180 out of phase with respect to at least one other of the pickup coils.

17. A passive noise reduction device according to claim 1, wherein the device coil is connected to the pickup coil by an electrically shielded connecting conductor, and wherein the shield is connected to ground.

18. A passive noise reduction device according to claim 17, wherein the electrically shielded connecting conductor comprises a coaxial conductor.

19. A passive noise reduction device according to claim 1, wherein the device coil does not require shielding from electromagnetic noise.

20. A passive noise reduction device according to claim 1, wherein the noise reduction device does not require further electrical components, such as: a resistor, a capacitor, an amplifier, a differential amplifier, or the like, or multiples and/or combinations of such electrical components.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:

(2) FIG. 1 is a perspective view of a prior art device;

(3) FIG. 2 is a perspective view of a prior art device;

(4) FIG. 3 is a perspective view of a prior art device, along with a diagrammatic representation of an electrical circuit for that device;

(5) FIG. 4 is a perspective view of a prior art device, along with a diagrammatic representation of an electric circuit for that device;

(6) FIG. 5 is a perspective view of an embodiment of the present invention;

(7) FIG. 6 is a cross-sectional view across line A-A from FIG. 5;

(8) FIG. 7 is a perspective view of another embodiment of the present invention;

(9) FIG. 8 is a cross-sectional view across line B-B from FIG. 7;

(10) FIG. 9 is a larger perspective view of the embodiment shown in FIG. 5;

(11) FIG. 10 is a perspective view of yet another embodiment of the present invention;

(12) FIG. 11 is a perspective view of an alternative embodiment of the present invention;

(13) FIG. 12 is a top plan view of a first possible shape in an embodiment of the present invention;

(14) FIG. 13 is a top plan view of a second possible shape in an embodiment of the present invention;

(15) FIG. 14 is a top plan view of a third possible shape in an embodiment of the present invention;

(16) FIG. 15 is a top plan view of a fourth possible shape in an embodiment of the present invention;

(17) FIG. 16 is a top plan view of a fifth possible shape in an embodiment of the present invention;

(18) FIG. 17 is a top plan view of an embodiment of the present invention including four coils;

(19) FIG. 18 is a top plan view of an embodiment of the present invention including three coils;

(20) FIG. 19 is a top plan view of a guitar showing two alternative embodiments of the present invention in situ;

(21) FIG. 20 is a circuit diagram showing an optional embodiment of the present invention, including a potentiometer;

(22) FIG. 21 is a graph showing a projected line of results based on a plurality of measurements for impedance of a single coil pickup at variable ambient temperatures;

(23) FIG. 22 is a representation of an experimental setup for assessing the noise reduction device;

(24) FIG. 23 is a graph showing partial results of an assessment using the setup shown in FIG. 22; and,

(25) FIG. 24 is a graph showing partial results of an assessment using the setup in FIG. 22.

DETAILED DESCRIPTION OF OPTIONAL EMBODIMENTS OF THE INVENTION

(26) To reduce hum and noise from a single coil pickup, it may be desired to introduce a circuit/coil/antenna that can also pickup such hum and noise. It may be desirable for such a system to passively introduce a same or similar amount of noise to a single coil pickup, wherein that noise is carried by a signal which is approximately 180 out of phase with the noise signal emanating from the single coil pickup.

(27) With this in mind, the present invention provides, in embodiments, a device which is designed to be able to remove, or at least reduce the noise from an instrument's single coil pickup or pickups, without substantially altering the tone or other musical qualities of the pickup or pickups. The present noise reduction device is wound differently, and is of a different size and impedance, when compared with other prior art devices.

(28) The inventor has found that configuring the present noise reduction device to have an impedance value, which value varies similarly to the impedance value of a single coil pickup at various ambient temperatures, results in a noise reduction device which produces little or no perceptible audio difference to the sound quality of a single coil pickup.

(29) The inventor has also found that the coil or coils in embodiments of the present noise reduction device produce sufficient noise electrical signal component values, such that noise generating a noise electrical signal component in a pickup coil is effectively countered, when the pickup noise electrical signal component is substantially 180 degrees out of phase with respect to the device noise electrical signal component.

(30) In embodiments, the wire coil of the noise reduction device may be wound with 34 AWG to 42 AWG wire. The length of the wire to be coiled for the noise reduction device is such that the resulting impedance of the coil is between approximately 100 and 1200. To accord with the formula the parameters will depend on the resistance of the pickup coil.

(31) In embodiments, the present invention has a low reactive inductance value, typically, 0.01H to 0.04H. Configuring the noise reduction device with such a reactive inductance value causes little effect to the tone of the single coil pickup.

(32) An embodiment of the present noise reduction device 100 is shown in FIG. 5. The device 100 includes a wire coil 102, which is wound in a particular chiral direction, that is, a left-handed winding or a right-handed winding. Alternatively, this can be called a clockwise winding or an anticlockwise winding. The winding of the coil will be determined based on the winding of the corresponding single coil pick up to which the device 100 is connected. In order to produce a noise electrical signal component in the coil of the device which is substantially 180 out of phase with respect to the noise electrical signal component produced in the single coil pickup, the winding of the device coil would need to be in an opposite direction to the winding of the single coil pickup coil, that is, if the single coil pickup coil is wound in a clockwise direction, the device coil will be wound in an anti-clockwise direction.

(33) The coil 102 of the device 100 has an insulating cover 104. The insulating cover may be formed from plastic or other insulating material or materials. The cover can be a preformed plastic substrate which accepts the coil wire when it is wound to form the coil, and can then be folded over the coil when wound. The cover must allow for emergence of terminals 106 and 108 for connection respectively, to the single coil pickup and to ground.

(34) In some embodiments, the section of wire leading from the terminal 106 to the corresponding terminal of the single coil pickup may electrically shielded, for example, by a foil tube. The shield is connected to earth. This shielding can eliminate or substantially ameliorate electrical noise signals form the section of wire, but without substantially negatively affecting the tone qualities due to the device coil remaining unshielded. Similar shielding may be used for the section of wire leading from the terminal 108 to earth.

(35) In an alternative embodiment, the cover 104 can be formed from plastic insulating tape. In such an embodiment, the coil wire can be wound, with or without a substrate, and when the coil has been wound, the tape can be wrapped helically around the wound coil. Again, the tape must allow for terminals 106 and 108 to protrude through the cover for connection.

(36) It should also be understood that the wire coil 102 of the device 100 does not need to be covered. It is possible to form the coil 102 with, for example, copper wire, and to not use a cover. Further, it is possible to form the coil 102 using self-bond wire.

(37) FIG. 6 shows a cross-sectional view across line A-A from FIG. 5. It can be more-clearly seen in FIG. 6 that the coil 102 of the device 100 is composed, in this embodiment, of approximately thirty loops of coil wire 110. It will be appreciated that the number of coils can be greater or lesser, depending on the desired impedance and/or inductance for the device 100, and depending on the gauge and properties of the wire used.

(38) In FIG. 6, it can be seen that the configuration of the windings 110 of the coil 102 is relatively flat, such that the wire coil forms a free-shaped ring, which is somewhat ribbon-like. Such a cross-sectional profile for the coil 102 can be useful, if it is desired to fit the coil within a narrower cavity space in a musical instrument.

(39) FIG. 7 shows an alternative embodiment of the device 100, having a coil 102, which is wound so as to have a more circular cross-sectional profile. This can be seen more clearly in FIG. 8, which is a cross-sectional view across line B-B from FIG. 7.

(40) This bunch wound configuration, as shown in FIGS. 7 and 8, may be more useful in an application where it is desired to insert the coil in a cavity space which is lower and wider, within a musical instrument.

(41) FIG. 9 shows a more-magnified view of the embodiment already shown in FIG. 5.

(42) In FIG. 10 there is shown an embodiment wherein there are two coils 102, 102 in the device 100. One coil 102 is reverse wound with respect to the other coil 102. In other words, one coil 102 may have a clockwise winding, whereas the other coil 102 has an anticlockwise winding. It will be appreciated that, in other embodiments, there may be 3, 4, 5, 6 or more coils in a single pickup.

(43) Each coil has its respective terminals, with coil 102 having terminal 106 to a first single coil pickup, and terminal 108 to ground. Coil 102 has terminal 112 to a second single coil pickup and terminal 114 to ground. It will be appreciated that, in other embodiments, the instrument may include more than two pickups. Further, the instrument may have a mixture of single coil pickups and other types of pickups, whether or not such other types of pickups can employ the present invention.

(44) It will be appreciated that the embodiment of the device 100, as shown in FIG. 10, would be suitable for use with an instrument having two single coil pickups, wherein a first of the two pickups includes a coil wound in one direction, whereas the second pickup includes a coil wound in an opposite direction from the coil of the first pickup.

(45) FIG. 11 also shows a device 100 with two separate coils 102, 102. In this embodiment, one coil 102 is wound anticlockwise, whereas the other coil 102 is wound clockwise. Terminals of the coils emanate from opposite sides of the device 100.

(46) FIGS. 12, 13, 14, 15 and 16, each show a different embodiment of the device 100 having a single coil 102. The coil forms a free-shaped ring, which can be manipulated to form a range of shapes, which are suitable for allowing the coil to be placed within a complementary-shaped cavity within a musical instrument. It will be understood that other embodiments of the device can be formed with a fixed shape, which is pre-designed for insertion into a known shaped cavity of a particular electrical stringed instrument.

(47) FIG. 12 shows a clover shaped configuration for the free-shaped ring. This configuration may be suitable for inserting the device 100 into a cavity surrounding the electrical circuitry and control knobs (pots) of a particular electric guitar brand.

(48) FIG. 13 shows a coil 102 of the device 100, which has a rectangular shape 118, which will be suitable for use in a corresponding rectangular shaped cavity in a musical instrument.

(49) FIG. 14 shows a configuration of the coil 102 having a shape 120 resembling a series of chevrons 122. Such a configuration may be suitable for insertion into a cavity surrounding single coil pickups in certain guitar designs.

(50) FIG. 15 shows a shoe-shape 124 for the coil 102 of the device 100, which may be suitable for placing in a cavity containing electrical circuitry and control devices in a particular electrical guitar design.

(51) FIG. 16 shows yet another embodiment of a single coil 102 for the device 100, which is a hammer shape 126.

(52) FIGS. 17 and 18 show various embodiments of shapes and number of coils for multi-coil designs for the device 100.

(53) FIG. 17 shows a device 100 having a series of coils 102 with one major coil 130 and three minor coils 132. The configuration of the coils into this particular shape 128 can be useful for inserting such coils in different cavities in the body of a stringed musical instrument.

(54) FIG. 18 is also a series of coils 102 including three chevron-shaped coils 136, which form a configuration 134 suitable for placement within cavities of a musical instrument.

(55) FIG. 19 shows an example application of the noise reduction device 100 within an electric guitar 138. The guitar includes three single coil pickups, including a front pickup 140, a middle pickup 142 and a back pickup 144. The guitar also includes electrical circuitry and control knobs (pots) 146.

(56) In this particular guitar 138, the pickups 140, 142 and 144, along with the circuitry and control knobs 146, are all located within the one cavity space 148.

(57) FIG. 19 shows that it is possible to fit two differently shaped configurations of the device 100 within the cavity space 148. A first configuration, similar to the configuration shown in FIG. 14, can be placed around the pickups. Another configuration of the device, similar to that shown in FIG. 15, can be placed within the cavity space 148 surrounding the control circuitry and knobs 146.

(58) In some applications, it is conceivable that both configurations 120 and 124 of the device 100 may be desired for use within the one electric guitar 138.

(59) FIG. 20 is a circuit diagram 160 showing the device 100 connected in series, via terminal 106, to a single coil pickup 162. The single coil pickup is then connected in series to a signal output 168. The device coil 102 is connected in series via terminal 108 to around 170.

(60) The circuit diagram 160 shows that the device 100 may be provided with an optional balance pot or potentiometer 166. The potentiometer is not required for effective noise reduction produced by the device 100, but can be used to provide favourable tonal qualities to the music signal.

(61) FIG. 21 shows a graph 172 having a Y-axis indicating temperature variance from 0 C. to 40 C., along with an X-axis showing impedance in k in a range from 6.5 k to 9.0 k. The graph 172 is an indication of variance in impedance in the coil of a single coil pickup at various ambient temperatures.

(62) The projected results line 178 in the graph 172 was produced using actual measurements of impedance of a single coil pickup at 0 C., 18 C. and 32 C. As can be seen from the projected line 178, there appears to be a linear relationship between ambient temperature and the expected impedance of a single coil pickup.

(63) It has been discovered that the coil 102 in the device 100 can be configured so as to produce an impedance which varies with temperature similarly to how the impedance in a given single coil pickup will vary with the same temperature. It should be emphasized that the quantum of impedance in the single coil pickup and the coil of the noise reduction device is not necessarily the same, but the change in impedance at given temperatures is sufficiently similar.

(64) FIG. 22 shows a diagrammatic representation of a setup 200 for assessing the noise reduction device 100 when used with a single coil pickup 206. The pickup used for this example assessment is a Fender 62 re-issue single coil pickup with an impedance of 5.6 k.

(65) The noise reduction device 100 and the single coil pickup 206 are shown lying in a single plane, as would be the case with many embodiments of the invention, where the noise reduction device is situated in, for example, a guitar. For this example setup, the noise reduction device coil is formed from #38AWG wire in a coil of the wire at 680 impedance.

(66) A noise source 202 is placed at a distance of one meter away from the centre point between the noise reduction device and the single coil pickup. It will be understood that the noise source 202 is situated perpendicular to the plane of the noise reduction device and the single pickup coil, with the signal noise from the source transmitting along line 212, and propagating symmetrically outward from line 212 towards the noise reduction device and the single pickup coil.

(67) Axes 208 show the direction of propagation of electromagnetic waves from the noise source 202, along the zero degree axis. Similarly, axes 210 show the direction of propagation of electromagnetic waves towards the single pickup coil 206, along the 0 axis.

(68) In this setup 200, the noise signals introduced into the single coil pickup 206 and into the noise reduction device 100 are separately measured as peak-to-peak voltage (Vpp). The Vpp is measured in graduated degrees of offset from the 0 axis, wherein the offset is measured in 10 incremental steps.

(69) FIGS. 23 and 24, respectively, show the results from an assessment using the setup 200 shown in FIG. 22 for the single coil pickup 206 and the noise reduction device 100.

(70) FIG. 23 shows the graph 300 for Vpp/degrees of offset in the single coil pickup 206. The plotted line 302 traces through the Vpp at each 10 increment, from 80 offset to 90 offset about the 0 axis in axes 210.

(71) FIG. 24 shows graph 400 of Vpp/degrees of offset for the noise reduction device 100, with line 402 being plotted through the result point of Vpp at each 10 increment from 80 to 90 about the 0 axis on axes 208.

(72) The noise source 202 in FIG. 22 is generating a 50 Hz noise signal. The noise signal is amplified by a factor of 20 by an amplifier (not shown).

(73) The assessment using the setup 200 shows that noise introduced into the single coil pickup 206 and the noise reduction device 100 are very similar. The profiles of the plotted lines 302 and 402 demonstrate this quite clearly. Accordingly, the noise reduction device will result in noise reduction where that device 100 is placed in series with the single coil pickup 206 and 180 out of phase (50 Hz signal).

(74) It will be understood that an assessment could be made with different sorts of setup, which are variations of the setup 200 shown in FIG. 22. For example, the noise source 202 could be at a different distance from the noise reduction device 100 and single coil pickup 206. the frequency of the signal could be different from that producing the results shown in FIGS. 23 and 24. Many other variations are also possible.

(75) In one example embodiment, is approximately 1.6810.sup.8 .Math.m (for copper wire); L is approximately 345 meters; A is approximately 810.sup.9 m2; leading to R being approximately 5.81 k.

(76) It has been found that when using a single coil pickup having approximately 5.8 k resistance and a coil wound with copper wire of 44 AWG, the best tones qualities of the device occur when the cross-sectional area, A, of the conductor in the device coil is chosen to be consistent with 38 AWG or 39 AWG. The tone drops in quality when larger or smaller diameter wire is used in the device coil.

(77) Passive, noise reduction is desirable where background noise is an issue for electromagnetic pickup device within stringed musical instruments. Further it is desirable to reduce noise without changing the original timbre or tone of a single coil pickup.

(78) The noise reduction device may also be used in other applications where background noise may be an issue. Such further applications include, for example, imaging, scanning or scientific research machinery and/or instruments, where such machinery and/or instruments require passive noise reduction.

(79) The present invention may be implemented according to any one or more of the above-mentioned embodiments. It will also be recognised by a person skilled in the art that other embodiments are possible, and should be considered to fall within the scope of the claimed invention.

(80) Throughout this specification and the claims which follow, unless the context requires otherwise, the word comprise, and variations such as comprises and comprising, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

(81) The reference to any prior art in this specification is not and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.