Patent Publication Number: US-11388521-B2

Title: Transducer arrangement

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. application Ser. No. 16/609,328, filed Oct. 29, 2019, which is a national phase application of international application no. PCT/FI2018/050740, filed Oct. 15, 2018, which claims priority from Finnish Application No. 20185251, filed Mar. 16, 2018 and Finnish Application No. 20175942, filed Oct. 25, 2017, which are incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     Field 
     The invention relates to transducers, such as loudspeakers, for converting electrical energy into vibration. 
     Description of the Related Art 
     Transducers may convert energy from one form to another and are applied in devices like the loudspeakers. Loudspeakers are widely used in many different places to produce a sound. An application WO 2016/079385 discloses a loudspeaker apparatus. The loudspeaker apparatus comprises a first magnet coupled with a surface and a second magnet coupled with a base. The loudspeaker apparatus further comprises at least one supporting member. The first magnet, the second magnet and the supporting member keep the surface in an equilibrium state. The first and the second magnets are arranged to face each other and a coil is arranged between the magnets to generate a force when an electrical signal is fed into the coil. The force breaks the equilibrium state of the surface. It may be beneficial to provide further solutions that may, for example, be applicable to the described arrangement. For example, further solutions for enabling equilibrium state may be beneficial. 
     SUMMARY 
     According to an aspect of there is provided the subject matter of the independent claims. 
     Some embodiments are described in the dependent claims. 
     According to an aspect there is provided an arrangement for generating vibration according to an electrical input signal, the arrangement comprising: a first permanent magnet configured to be coupled with a surface of an apparatus; a second permanent magnet configured to be coupled with a base of the apparatus, the first and second permanent magnets configured to be arranged to face each other and to cause a first force to the surface; and a coil coupled with an input for receiving an electrical input signal, the coil configured to generate a magnetic field according to the electrical input signal in order to displace the surface to generate vibration, wherein the arrangement further comprises: a first magnetic object configured to be coupled with the surface and to at least partially encircle the first permanent magnet; and a second magnetic object configured to be coupled with the base and to at least partially encircle the second permanent magnet, wherein at least one of the first and second magnetic objects comprises a permanent magnet, the first and second magnetic objects configured to be arranged to face each other and to cause a second force to the surface having an opposite direction compared with the first force. 
     In an embodiment, the coil is configured to be arranged between the first and second permanent magnets. 
     In an embodiment, the coil is configured to be arranged around one of the first permanent magnet and second permanent magnet. 
     In an embodiment, the arrangement is for generating an audio output according to the electrical input signal. 
     In an embodiment, the second magnetic object comprises a permanent magnet. 
     In an embodiment, the first magnetic object comprises a permanent magnet. 
     In an embodiment, a first pole of the first permanent magnet faces the second permanent magnet, and wherein a second pole of the first permanent magnet is fixed to the first magnetic object to magnetize the first magnetic object facing the second magnetic object. 
     In an embodiment, the first magnetic object encircles the first permanent magnet and the second magnetic object encircles the second permanent magnet, and wherein at least one of the first magnetic object, the second magnetic object comprises an axially magnetized permanent ring magnet. 
     In an embodiment, said coil is a first coil configured to generate a first magnetic field according to the electrical input signal, the arrangement further comprising: a second coil arranged between the first and second magnetic objects and configured to generate a second magnetic field according to an electrical input signal. 
     In an embodiment, the arrangement further comprises: means for shifting phase of the electrical input signal such that a phase of the electrical input signal inputted into the first coil is substantially 180 degrees different compared with a phase of the electrical input signal inputted into the second coil. 
     In an embodiment, a winding of the first coil is opposite to a winding of the second coil. 
     In an embodiment, the arrangement further comprises: at least one further element comprising magnetic material and arranged between the first permanent magnet and a permanent magnet of the first magnetic object and/or between the second permanent magnet and a permanent magnet of the second magnetic object. 
     In an embodiment, the at least one further element comprises a core of an axially magnetized permanent ring magnet comprised in the first magnetic object and/or the second magnetic object. 
     In an embodiment, the at least one further element comprises a cavity for the first permanent magnet and/or the second permanent magnet. 
     In an embodiment, the first and second forces are of substantially equal magnitude. 
     According to an aspect there is provided an apparatus comprising: a surface; a base; and at least one of said arrangement for generating vibration according to an electrical input signal. 
     According to an aspect there is provided a method of manufacturing an arrangement generating vibration according to an electrical input signal, the method comprising: coupling a first permanent magnet with a surface of an apparatus; coupling a second permanent magnet with a base of the apparatus, the first and second permanent magnets arranged to face each other and to cause a first force to the surface; arranging a coil between the first and second permanent magnets, the coil coupled with an input for receiving an electrical input signal, the coil configured to generate a magnetic field according to the electrical input signal in order to displace the surface to generate vibration; the method further comprising: coupling a first magnetic object with the surface such that the first magnetic object at least partially encircles the first permanent magnet; coupling a second magnetic object with the base such that the second magnetic object at least partially encircles the second permanent magnet, wherein at least one of the first and second magnetic objects comprises a permanent magnet, the first and second magnetic objects arranged to face each other and to cause a second force to the surface having an opposite direction compared with the first force. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which 
         FIG. 1  illustrates a cross sectional view of an arrangement to which embodiments of the invention may be applied; 
         FIG. 2  illustrates a cross sectional view of an embodiment; 
         FIG. 3  illustrates a cross sectional view of an embodiment; 
         FIGS. 4A and 4B  illustrate some embodiments; 
         FIGS. 5A and 5B  illustrate a cross sectional view of some embodiments; 
         FIGS. 6A and 6B  illustrate a top view of an arrangement according some embodiments; 
         FIGS. 7A, 7B and 7C  illustrate some embodiments; 
         FIG. 8  illustrates an embodiment; 
         FIG. 9  illustrates a flow diagram according to an embodiment; 
         FIG. 10  illustrates an arrangement according to an embodiment; and 
         FIGS. 11, 12, 13, 14, 15 and 16  illustrate some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The following embodiments are exemplifying. Although the specification may refer to “an”, “one”, or “some” embodiment(s) in several locations of the text, this does not necessarily mean that each reference is made to the same embodiment(s), or that a particular feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. 
     WO2016079385 is incorporated herein as a reference in its entirety. 
       FIG. 1  shows an arrangement  10  for generating vibration, such as haptic output (e.g. haptic feedback) or audio output (e.g. audio feedback). Referring to  FIG. 1 , the arrangement  10  comprises: a surface  102  arranged to be mechanically displaced, a first magnet  110  coupled with the surface  102 , at least one supporting member  108  for supporting the surface  102 , a base  104 , a second magnet  120  coupled with the base  104 , wherein the second magnet  120  is arranged to face the first magnet  110  as shown in  FIG. 1 . The arrangement  10  may further comprise a coil  122  arranged between the first and second magnets  110 ,  120 , and an input  130  (e.g. signal port) electrically coupled with the coil  122 , wherein an electrical signal is configured to travel between the signal port  130  and the coil  122 . A magnetic field between the first magnet  110  and the second magnet  120  causes a force to the surface  102 , wherein an entity, comprising the surface  102  and the at least one supporting member  108 , comprises at least one elastic element providing a supporting counterforce acting as a counterforce to the force caused by the magnetic field, causing the surface  102  to be in a force equilibrium state, and wherein the electrical signal in the coil  122  is proportional to mechanic displacement of the surface  102  when the force equilibrium state is broken either by the electrical signal in the coil  122  or the mechanic displacement of the surface  102  from a position of the force equilibrium state. That is, when an electrical signal is fed via the input  130  to the coil  122 , the force equilibrium may be broken. Hence, the surface  102  may be caused to vibrate (indicated with arrow  103 ) according to the electrical input signal. It is further noted that the surface  102  may be supported by the at least one supporting member  108 , e.g. the surface  102  may be coupled with the at least one supporting member from area(s)  101 . For example, the surface  102  may thus be supported with respect to the base  104  (e.g. the member(s)  108  may be comprised in the base  104 ). For example, the arrangement  10  may be for generating an audio output according to the electrical input signal. Audio output may mean and/or comprise sound that is detectable by human ear, i.e. sound that may be heard by a human. In some examples, it may refer to sound that is detectable by animal(s) and/or audio sensors (e.g. microphone). For example, the audio output may comprise music, speech, sound effects and the like. It is also pointed out that the surface  102  and the base  104  may be parts of an apparatus, such as a mobile phone, television, computer, music player, or some other type of user device. For example, the base  104  may form at least a part of a frame of the apparatus. For example, the surface  102  may be or be comprised in a screen of the apparatus (e.g. electronic apparatus). For example, the provide solution may be applicable to automotive industry (e.g. cars). For example, the surface  102  may comprise car panels such as car interior panel (e.g. door panel, ceiling or roof panel, wall panel, frame panel, or some other part of the car interior. For example, the surface  102  may comprise car display. For example, the surface  102  may be comprised in a wearable device, such as wearable electronic device. For example, the surface  102  may be comprised a portable electronic device, such as a watch or wrist device (e.g. surface  102  may be comprised in a display of such device). 
     There is provided a further solution which may be applicable for the arrangement  10  of  FIG. 1 . Said further solution is discussed now in more detail.  FIG. 2  illustrates an embodiment. Referring to  FIG. 2 , an arrangement  100  for generating vibration according to an electrical input signal is shown. The arrangement  100  comprises: the first permanent magnet  110  configured to be coupled with the surface  102  of an apparatus; the second permanent magnet  120  configured to be coupled with the base  104  of the apparatus, the first and second permanent magnets  110 ,  120  configured to be arranged to face each other and to cause a first force to the surface  102 ; and the coil  122  arranged between the first and second permanent magnets  110 ,  120  and coupled with the input  130  for receiving an electrical input signal, the coil  122  configured to generate a magnetic field according to the electrical input signal in order to displace the surface  102  to generate vibration (e.g. shown in  FIG. 1  with arrows  103 ). The arrangement  100  further comprises a first magnetic object  210  configured to be coupled with the surface  102 , and a second magnetic object  220  configured to be coupled with the base  104 . The first and second magnetic objects  210 ,  220  are configured to be arranged to face each other and to cause a second force to the surface  102  having an opposite direction compared with the first force (i.e. force caused by the first and second permanent magnets  110 ,  120  to the surface  102 ). Hence, the second force may further be used to acquire the force equilibrium state discussed with respect to  FIG. 1 . This may provide additional benefits. For example, the strain on the surface  102  may be reduce as the opposing force may be inflicted to the surface in a more even manner compared with a solution where the counterforce is inflicted from edge areas of the surface  102 . Such counterforce may cause bending of the surface  102  which may be reduced by using the objects  210 ,  220  as described. Another benefit may be that stronger permanent magnets  110 ,  120  may be used as there is possibility to provide a counterforce to the stronger permanent magnets. It is also pointed out that the bending of the surface  102  may also produce counterforce, and can be used to provide at least some of the counterforce in some embodiments. Similar or same effect can be achieved utilizing the solution described, for example, with reference to  FIGS. 11, 12, 13, 14, 15 , and/or  16 . 
     In an alternative embodiment, the coil  122  is placed between the magnetic objects  210 ,  220  instead of placement between the permanent magnets  110 ,  120 . 
     As shown in  FIGS. 1 and 2 , the permanent magnets  110 ,  120  may be arranged to be at a distance from each other. Similarly, the objects  210 ,  220  may be arranged to be at a distance from each other. This may enable the surface  102  to vibrate according to the signal in the coil  122 . It is also pointed out that the surface  102  may be at a distance from the base  104  from at least some areas. I.e. the surface  102  is hangably arranged, pre-tensioned and/or otherwise arranged such that it may vibrate. 
     To further enhance the solution, the placement of the first and second magnetic objects  210 ,  220  may be such that the first magnetic object  210  at least partially encircles and/or surrounds the first permanent magnet  110 , and the second magnetic object  220  at least partially encircles and/or surrounds the second permanent magnet  120 . The encircling may be such that the object  210 ,  220  fully encircles the corresponding magnet or at least extends to opposite sides of the respective magnet (i.e. permanent magnet  110 ,  120  is placed between at least two portions of the respective magnetic object  210 ,  220 ). It is also possible that the magnetic object  210 ,  220  is made of pieces which at least partially encircle the respective permanent magnet  110 ,  120 , meaning that not all parts of the magnetic objects  210 ,  220  are necessarily magnetic. 
     There are different possibilities to achieve the second force (also referred to as counterforce) cause by the magnetic interaction between the first and second magnetic objects  210 ,  220 . In one example at least one of the first and second magnetic objects  210 ,  220  is a permanent magnet (e.g. one is permanent magnet and other comprises magnetic material or both are permanent magnets). 
     It is noted that the first magnetic object  210  may be placed at a distance from the first permanent magnet  110  as shown in  FIG. 2 . Similarly, there may be a certain gap between second magnetic object  220  and the second permanent magnet  120 . Using the gap therebetween may reduce the interaction of magnetic forces between the second permanent magnet  120  and the first magnetic object  210 , for example. Similarly, the gap may reduce the interaction of magnetic forces between the first permanent magnet  110  and the second magnetic object  220 . Therefore, using the gap may further improve the provided solution. The distance or gap between the first magnetic object  210  and the first permanent magnet  110  and/or between the second magnetic object  220  and the second permanent magnet  120  may be, for example, at least 1 millimetre (mm), 5 mm, 1 centimetre (cm), 2 cm, 3 cm, 4 cm, 5 cm, 10 cm or more. The gap may refer to air gap or some other gas, or may comprise some substantially non-magnetic material. As discussed later, magnetic material may also be used between the magnets and magnetic objects. 
     It is noted that the coupling of a magnet or magnetic object with the surface  102  or the base  104  may refer to fixing or attaching said magnet or magnetic object to the surface  102  or the base  104 . Such fixing may be achieved using, for example, glue and/or screws. In some examples, the different magnet(s) and/or magnetic object(s) may be printed on the surface  102  and/or the base  104 . Hence, the coupling may also comprise printing (e.g. electronics printing). Further, the arrangement of the coil  122  between the permanent magnets  110 ,  120  may comprise coupling (e.g. fixing or attaching) the coil  122  with the second permanent magnet  120  or with the first permanent magnet  110 . However, it may also be possible to use separate elements to arrange the coil  122  between the permanent magnets  110 ,  120  such that it does not physically touch neither of said permanent magnets  110 ,  120 . For example, said element(s) may be attached to the base  104  or some other part of the arrangement, and reach to the area between the permanent magnets  110 ,  120 . Similar, attachment with respect to possibly used further coil (e.g. coil  722 ) may be used. 
     Also, the surface  102  may be supported with respect to the base  104  using a plurality of different solutions. For example, one or more elastic and/or flexible elements may be used to support the surface  102 . In one example, the one or more elastic and/or flexible elements comprise spring(s) disposed between the surface  102  and the base  104 . However, these may not necessarily be needed as the counterforce may be partially or entirely achieved using the magnetic objects  210 ,  220 . Hence, these one or more elastic and/or flexible elements are not discussed in further detail. It may suffice that the surface  102  may be supported from at least one area  101  with respect to the base  104  (e.g. edge area  101  of the surface  102 , such as a screen). The supporting on the area(s)  101  may be at least partially elastic and/or comprise clearance such that the surface  102  may move also from the edge areas with respect to the base  104  according to the electronic signal inputted via the input  130  to the coil  122 . 
     According to an embodiment, the provided arrangement comprises one or more elastic elements (e.g. springs) disposed between the elements  310  and  320  (e.g. fixed to both elements to provide the counterforce). Similarly, in cases where only two magnets are used (e.g. magnets  110 ,  120 ) the springs may be arranged between bases coupled (e.g. fixed) with the magnets. So, for example, magnet  110  may comprise or be coupled with a base. So, for example, magnet  120  may comprise or be coupled with a base. Hence, the springs or similar elements may be connected to said bases. So, as described, the arrangements does not initially necessarily require the surface  102  and the base  104 , but may be arranged in such system or apparatus comprising the surface  102  and the base  104  with minimum effort as the arrangement may already be configured to be in equilibrium state. 
     It is also pointed out that the surface  102  may be rigid (i.e. bends very little or not at all, e.g. inflexible). The surface  102  may comprise, for example, a plane. The surface  102  may comprise, for example, metal, wood, glass, and/or plastics. In an embodiment, the thickness of the surface  102  is at least 1 mm, 2 mm, 3 mm, or 5 mm. In an embodiment, the thickness of the surface  102  is at least 1 cm. In an embodiment, the thickness of the surface  102  is at least 2 cm. In an embodiment, the thickness of the surface  102  is at least 5 cm. 
       FIG. 3  shows the arrangement  100  according to an embodiment. Referring to  FIG. 3 , the first and second magnetic objects  210 ,  220  each comprise a permanent magnet  211 ,  221 . The number of permanent magnets is not necessarily limited to two, but two may suffice at least in some examples (e.g. ring magnets). In the example of  FIG. 3 , the first and second permanent magnets  110 ,  120  cause a force that pushes the magnets  110 ,  120  away from each other). However, the first and second magnetic objects  210 ,  220  (or more precisely their permanent magnets  211 ,  221 ) are placed such that they pull each other. Hence, the overall force to the surface  102  may be sum of said two pushing and pulling forces. Naturally, the forces may be arranged other way around (i.e. permanent magnets  110 ,  120  pull each other and permanent magnets  211 ,  221  push each other). 
     Previously, it was discussed that there may be a gap between the magnetic object  210  and the permanent magnet  110 , and similarly, between the magnetic object  220  and the permanent magnet  120 . In an embodiment, the arrangement  100  further comprises at least one further element  310 ,  320  comprising magnetic material. For example, a first further element  310  may be arranged between the first permanent magnet  110  and between the permanent magnet  211  of the first magnetic object  210 . For example, a second further element  320  may be arranged between the second permanent magnet  120  and the permanent magnet  221  of the second magnetic object  220 . The at least one further element  310 ,  320  may act as a buffer between the magnets  211 ,  110 , and between the magnets  221 ,  120 . Buffer here may mean that the magnetic interaction reduced using the gap described earlier may be further reduced using the at least one further element  310 ,  320  between the permanent magnets. Hence, there may be no need for the gap(s), and thus smaller devices may be achieved. However, in addition to the at least one further element  310 ,  320 , the gap or gaps between the magnets may be used. For example, the at least one further element  310 ,  320  comprises and/or is made of ferromagnetic and/or ferrimagnetic material(s), such as iron. 
     In an embodiment, the first magnetic object  210  is coupled (e.g. attached or fixed) to the first element  310 . 
     In an embodiment, the second magnetic object  220  is coupled (e.g. attached or fixed) to the second element  320 . 
     In an embodiment, the first permanent magnet  110  is coupled (e.g. attached or fixed) to the first element  310 . 
     In an embodiment, the second permanent magnet  120  is coupled (e.g. attached or fixed) to the second element  320 . 
     In an embodiment, the at least one further element  310 ,  320  comprises a core of an axially magnetized permanent ring magnet comprised in the first magnetic object  210  and/or the second magnetic object  220 . For example, the first element  310  may form the core of an axially magnetized permanent ring magnet  211 . For example, the second element  310  may form the core of an axially magnetized permanent ring magnet  221 . 
     In an embodiment, the at least one further element  310 ,  320  comprises a cavity for the first permanent magnet  110  and/or the second permanent magnet  120 . This may be shown in  FIG. 3  in which the first permanent magnet  110  may be placed in a cavity of the first element  310  forming the core of the ring magnet  211 . Similarly, the second permanent magnet  120  may be placed in a cavity of the second element  320  forming the core of the ring magnet  221 . The coil  122  may reach to the area of the at least one further element  310 ,  320  (e.g. between elements  310 ,  320 ). However, this may not be necessary. 
       FIGS. 4A and 4B  show some examples of different arrangements of the permanent magnets and/or magnetic objects. For example, with reference to  FIG. 4A , if the north poles of permanent magnets  110 ,  120  are placed to face each other, the magnetic objects  210 ,  220  may be arranged such that other provides a south pole and the other provides a north pole that are facing each other. Hence, the first force and the second force may be to opposite directions. With reference to  FIG. 4B , the second permanent magnet  120  is flipped and thus there is a pulling force between the magnets  110 ,  120 . Hence, it may be necessary to arrange at least one of the magnetic objects  210 ,  220  to achieve the opposing force therebetween. 
     Use of permanent magnets  211 ,  221  may not be necessary in all cases. Examples of such configurations may be shown in  FIGS. 5A and 5B  illustrating some embodiments. Referring to  FIGS. 5A and 5B , the first magnetic object  210  or the second magnetic object  220  may comprise an element  510  or  520 . Said element(s)  510 ,  520  may be made of and/or magnetic material, such as ferromagnetic and/or ferrimagnetic material. Hence, if the other one of the first and second magnetic objects  210 ,  220  comprises a permanent magnet, the element  510 ,  520  may be used to provide the counterforce similarly as in the situation where both magnetic objects  210 ,  220  comprise permanent magnets. 
     According to an embodiment (referring to  FIG. 5A ), a first pole of the first permanent magnet  110  faces the second permanent magnet  120 , wherein a second pole of the first permanent magnet  110  is fixed to the first magnetic object  210  to magnetize the first magnetic object  210  (or more particularly the element  510 ) facing the second magnetic object  220 . In such case the second magnetic object  220  may comprise a permanent magnet (e.g. permanent magnet  221  as shown in  FIG. 5A , for example. 
     According to an embodiment (referring to Figure SB), a first pole of the second permanent magnet  120  is arranged to face the first permanent magnet  110 , wherein a second pole of the second permanent magnet  120  is fixed to the second magnetic object  220  to magnetize the second magnetic object  220  (or more particularly the element  520 ) facing the first magnetic object  210 . In such case the first magnetic object  210  may comprise a permanent magnet (e.g. permanent magnet  211  as shown in  FIG. 5B ), for example. For example, first pole may be north and second pole may be south. Other way around, first pole may be south and second pole may be north. In the Figures (e.g.  FIGS. 5A and 5B ) one magnetic pole (e.g. first pole) may be indicated with a pattern fill comprising backslashes and the other magnetic pole (e.g. second pole) is indicated with a pattern fill comprising slashes or solidus. 
     As shown in  FIGS. 5A and 5B , if the magnetic object  210 ,  220  is magnetized using the permanent magnet  110 ,  120 , said magnetic object  210 ,  220  may be referred to as a magnetized element  510 ,  520  (i.e. magnetic object  210  is element  510  and magnetic object  220  is element  520 ). Accordingly, areas  512 ,  522  may be magnetized such that they enable to provide the counterforce. For example with reference to  FIG. 5A , if same poles of first and second permanent magnets  110 ,  120  are facing each other, the magnetized element  510  is drawn to the magnet  221  from the area  512  as the area  512  may be magnetized with the opposing pole (i.e. opposing to the pole facing the second permanent magnet  120 ) of the first permanent magnet  110 . Similarly, the area(s)  522  of  FIG. 5B  may be magnetized according to the same principles. So, for example, in Figure SA, areas  512  may be magnetized such that they represent second pole (i.e. backslash filled portions). 
     It is further noted that the element  510 ,  520  may comprise a cavity for the permanent magnet  110 ,  120 . It is further noted that said cavity may be such that the elongating area or areas  512 ,  522  are not in direct contact with the permanent magnet  110 ,  120  (as shown in Figure SB). Hence, the element  510 ,  520  and the permanent magnet  110 ,  120  may be arranged such that only one pole of said permanent magnet  110 ,  120  is in direct contact with the element  510 ,  520 , and thus the element  510 ,  520  may be magnetized with the needed pole (i.e. the same pole which is in contact with the permanent magnet  110 ,  120 ). 
       FIGS. 6A and 6B  illustrate birds-eye view of the arrangement  100  according to some embodiments. Referring to  FIG. 6A , a magnetic object  610  encircles a permanent magnet  630 . The magnetic object  610  may refer to one or both the first magnetic object  210  and the second magnetic object  220 . Correspondingly, the permanent magnet  630  may refer to one or both the first permanent magnet  110  and the second permanent magnet  120 . It needs to be noted that the encircling magnetic object  610  may be fully or partially magnetic as discussed above. 
     In an embodiment, the magnetic object  610  comprises an axially magnetized permanent ring magnet. That is, the ring magnet may encircle the permanent magnet  630 . 
     In an embodiment, with reference to  FIG. 6A , a further magnetic element  620  may be placed between the object  610  and the permanent magnet  630 . Said further element  620  may refer to one or both the element  310  and the element  320  of  FIG. 3 . According to one embodiment, the element  620  forms a core of the axially magnetized permanent ring magnet (i.e. comprised or forming element  610 ). The element  620  may further comprise a cavity or a slot for the permanent magnet  630 . Thus, the permanent magnet  630  may be embedded into the element  620 , and the element  620  may be embedded into the ring magnet (i.e. comprised or forming element  610 ). 
     Referring to  FIG. 6B , situation illustrated and discussed with respect to  FIGS. 5A and 5B  may be shown. That is, the permanent magnet  630  may be encircled by an element  640  (e.g. comprise ferromagnetic material) which may be magnetized by said permanent magnet  630 . As described, there may be a gap  650  between the permanent magnet  630  and the element  640 , the gap  650  enabling the permanent magnet  630  to be in contact with the element  640  via only one pole of the permanent magnet  630 . Said element  640  may refer to one or both the element  510  and element  520  of  FIGS. 5A and 5B . 
     In an embodiment, the permanent magnet  630  is a disc magnet, i.e. axially magnetized permanent disc magnet  630 . 
     For example, the element  620  may be a cylinder with a cylindrical cavity, wherein the disc magnet  630  may be placed in said cylindrical cavity. Said cavity may as well be rectangular, wherein the magnet  630  may thus be rectangular. The object  610  may surround the element  620 . In an embodiment, the object  610  is a cylinder (or of some other form) with a cylindrical cavity (or of some other form), wherein the element  620  may be placed in a cavity formed by said object  610 . 
       FIGS. 7A to 7C  illustrate some embodiments. According to an embodiment, the arrangement  100  further comprises a second coil  722  arranged between the first and second magnetic objects  210 ,  220  and configured to generate a second magnetic field according to an electrical input signal. The coil  122  (now referred to as a first coil  122 ) and the second coil  722  may be coupled with the same input  130  or with different inputs. Hence, the arrangement  100  may be used in a plurality of different ways to generate different magnetic fields in order to displace the surface  102  to generate vibration. If there is no input via the input  130  and/or some other input, the surface  102  may be in a force equilibrium state. However, when input is provided to the coil(s)  122 ,  722 , the equilibrium state may be broken. The second coil  722  may be coupled with the second magnetic object  220 . However, it may be coupled to the first magnetic object  210  or otherwise arranged between said objects  210 ,  220 . 
     Now, according to an embodiment, the coils  122 ,  722  are connected to the same input  130  (e.g.  FIG. 7A ). That is, same, identical or similar electrical input signal may be simultaneously inputted to both coils  122 ,  722 . According to an alternative embodiment, a different electrical signals may be inputted to both coils  122 ,  722  and/or the input signal(s) may be inputted at different time periods. 
     According to an embodiment, arrangement  100 , the coils  122 ,  722  and/or the input  130  is arranged such that when the magnetic fields generated by the coils  122 ,  722  both cause a force to the surface  102  that is substantially to the same direction (e.g. towards the base  104  or outwards from the base  104 ). There may be plurality of different ways to achieve this. However, there may be at least two solutions which may be used. 
     Referring to  FIG. 7B , the arrangement  100  further comprises a phase shifter  720  for shifting a phase of an electrical input signal such that a phase of the electrical input signal inputted into the first coil  122  is substantially 180 degrees different compared with a phase of an electrical input signal inputted into the second coil  722 . That is, if same or similar signal is used as an input, before the signal is inputted in the coils  122 ,  722 , the signal may be processed or altered (e.g. analogic and/or digital processing) such that the inputted signals to the coils are in antiphase with respect to each other. One example of such processing may be delaying the phase of the input signal to the second coil  722 . 
     Referring to  FIG. 7C , a winding of the first coil  122  may be opposite to a winding of the second coil  722 . E.g. if the winding of the first coil  122  is to direction  750 , the winding of the second coil  722  may be to opposite direction  760 . Hence, if an input signal having the same phase is inputted in to both coils  122 ,  722 , the coils may provide magnetic fields which are (at least) to substantially different directions, i.e. same or identical input signal is configured to be inputted to both coils  122 ,  722 . It is noted that the throughout the description, phrases like input signal or electrical input signal is used. Such may refer to an electrical input signal which has an alternating current (AC) component. Said signal may or may not have a direct current (DC) component. However, as generally known, the alternating current in a coil may cause the magnetic field. This is generally referred to as electromagnet functionality. 
     The coil(s)  122 ,  722  may be placed between the magnets  110 ,  120  and the magnetic objects  210 ,  220  such that the main force component caused, by the input signal(s), to the surface is substantially orthogonally towards or away from the base. E.g. the winding may be placed on the magnet  120  or object  220  as shown in  FIG. 7C  illustrating top view of the coils  122 ,  722 . 
     In an embodiment, the coil(s)  122 ,  722  have a core, such as an iron core. Said core may be orthogonal to the magnet  120  or the object  220  when the coil  122  or the second coil  722  is placed on said magnet  120  or on said object  220 . 
     In an embodiment, the first and second forces are of substantially equal magnitude. That is, the magnetic objects  210 ,  220  and the permanent magnets  110 ,  120  may be arranged, dimensioned and configured such that the forces are substantially equal. Hence, the strain to the surface  102  may further be reduced when the surface  102  is in the force equilibrium state. If the forces are unequal magnitude, the equilibrium state may be achieved using elastic elements (e.g.  108 ) and/or relying on the spring force caused by the bending surface  102 . 
     In an embodiment, the coil  722  is attached to a permanent magnet of the second magnetic object  220  or a permanent magnet of the first magnetic object  210 . For example, the coil  722  may be used in embodiments utilizing permanent magnet at both the first and second magnetic objects  210 ,  220  (e.g.  FIG. 3 ) and embodiments utilizing one permanent magnet and one magnetized element (e.g.  FIGS. 5A and 5B ). 
     It is further noted that although not shown in  FIG. 7C , the coils  122 ,  722  may be connected from other ends to ground potential such that a closed electrical circuit or circuits may be formed. This is believed to be well within capability of a skilled person and thus not explained in further detail. 
       FIG. 8  illustrates an embodiment. Referring to Figure, an apparatus  800  is shown. The apparatus  800  may comprise the surface  102  (e.g. a display of the apparatus  800 ) and the base  104  (not shown in  FIG. 8 ). Furthermore, the apparatus  800  may comprise at least one arrangement  100  as described above and/or below. The arrangement  100  is illustrated as arrangement  810 A and  810 B in  FIG. 8 . Using the arrangement(s)  100  in the apparatus  800  may remove the need to use an additional vibration element and/or speaker. Hence, there may be more room in the device for display, for example. Such may be a beneficial feature, for example, for mobile phones, televisions and the like. 
       FIG. 9  illustrates a flow diagram of a method of manufacturing an arrangement  100  generating vibration according to an electrical input signal, the method comprising: coupling a first permanent magnet with a surface of an apparatus (block  902 ); coupling a second permanent magnet with a base of the apparatus, the first and second permanent magnets arranged to face each other and to cause a first force to the surface (block  904 ); arranging a coil between the first and second permanent magnets, the coil coupled with an input for receiving an electrical input signal, the coil configured to generate a magnetic field according to the electrical input signal in order to displace the surface to generate vibration (block  906 ); coupling a first magnetic object with the surface such that the first magnetic object at least partially encircles the first permanent magnet (block  908 ); coupling a second magnetic object with the base such that the second magnetic object at least partially encircles the second permanent magnet (block  910 ), wherein at least one of the first and second magnetic objects comprises a permanent magnet, the first and second magnetic objects arranged to face each other and to cause a second force to the surface having an opposite direction compared with the first force. 
       FIG. 10  illustrates the arrangement  100  according to an embodiment. As shown in the Figure, the arrangement  100  does not necessarily comprise the surface  102  and the base  104 . However, the arrangement  100  may be arranged such that the arrangement  100  is attachable to the surface  102  and to the base  104 . Although in  FIG. 10  four permanent magnets are shown (i.e.  110 ,  120 ,  211 ,  221 ), the solution may be similarly applicable to solutions utilizing less permanent magnets (e.g.  FIGS. 5A and 5B ). For example, the magnets  120  and  221  may be attached to each other via the element  320 , and the coil  122  may attached to the formed first entity. A second entity may be formed by attaching the magnets  211  and  110  to each other via the element  310 . The second entity may then be attached to the surface  102  and the first entity to the base  104 , for example. In some cases, the attachment may be other way around (i.e. first entity may be attached to the surface  102 . It is also possible that the coil  722  is used in the embodiment of  FIG. 10  (i.e. examples of  FIGS. 7A to 7C ). Also, the springs or some other elastic elements (if used at all) may be arranged directly between the first and second entities (e.g. attached between said entities). Hence, the assembly comprising the first and second entities may be easily attached to a surface and a base of an apparatus to obtain a vibrating (e.g. sound generating apparatus). 
     As used in this application, ferromagnetic materials may comprise at least one of cobalt, iron, nickel, gadolinium, dysprosium, permalloy, awaruite, wairakite, and magnetite. In some embodiments, the ferromagnetic materials comprise two or more of said materials. For example, the permanent magnets described above may be made of and/or comprise the described materials. 
     In an embodiment, the first magnet  110  and/or the second magnet  120  are made and/or comprise neodymium and/or ferrite. In such case, the kJ/m 3  value of the first and/or second magnets  110 ,  120  may be between 250-400 kJ/m 3 , for example. Similarly, the other permanent magnets described above may comprise said material(s). 
     According to an aspect, there is provided an arrangement  100  for generating vibration according to an electrical input signal, the arrangement comprising: a first permanent magnet arrangement comprising a first permanent magnet  110 ; a frame  1110  comprising magnetic material; a second permanent magnet  120  configured to be arranged between the first permanent magnet  110  and the frame  1110  and to be coupled with the frame  1110 , one or more portion of the frame  1110  extending at least in one direction over an edge area of the second permanent magnet  120 , the second permanent magnet  120  further configured to face, at a distance, the first permanent magnet  110  such that a magnetic interaction between the first permanent magnet  110  and the second permanent magnet  120  causes a first force to a surface  102  of an apparatus, wherein the frame  1110  is configured to be magnetized by the second permanent magnet  120  in order to cause magnetic interaction between said one or more portion of the frame  1110  and the first permanent magnet arrangement in order to cause a second force to the surface  1110  having an opposite direction compared with the first force; and a coil  122  coupled with an input for receiving an electrical input signal, the coil configured to generate a magnetic field according to the electrical input signal in order to displace the surface to generate vibration. 
     As described, the one or more portions of the frame  1110  may extend at least in one direction over an edge area of the second permanent magnet  120 . So, for example, if the second permanent magnet  120  is situated on the frame  1110 , the surface area of the surface of the frame  1110  that is placed against the second permanent magnet  120  may be greater than the surface area of the surface of the second permanent magnet  120  that is placed against the frame  1110 , i.e. extend over the edge of the permanent magnet  120  at least in one direction. Hence, for example, the one or more parts of the frame  1110  may be visible in the top view of  FIG. 15 . The frame  1110  may also be, for example, circular or of some other shape. 
       FIGS. 11, 12, 13, 14, 15, and 16  illustrate some embodiments. The frame  1110  may be or be comprised in magnetic object  210  or  220 , or elements  310 ,  320 , for example. Hence, the frame may be similar as the magnetized elements  310 ,  320 , for example. However, according to an embodiment, the frame  1110  (and also the second frame  1120  if such is used, i.e.  1120  may not be necessary, but may be useful) is not a magnet or permanent magnet, but an element that comprises magnetic material that may be magnetized by using a permanent magnet (e.g. magnet  120 ), for example. For example, the second permanent magnet  120  may be physically coupled with the frame  1110  to magnetize the frame  1110 . 
       FIGS. 11, 12, and 13  show some embodiments in which the coil  122  is configured to be arranged to encircle the second permanent magnet  120 . I.e. the coil  122  is not necessarily between the permanent magnets  110 ,  120 . However, such solution may also be utilized. By encircling the permanent magnet  120  with the coil  122  may provide the benefit of reducing space between the magnets  110 ,  120 , for example. Hence, the first force may be increased, thus possibly providing more efficient solutions. In an embodiment, the coil  122  is configured to be looped around the second permanent magnet. Placing the coil  122  around the permanent magnet  120  or around the first permanent magnet  110  may also be used in other solutions described above. 
     According to an embodiment, the first permanent magnet arrangement is coupled with the surface  102  and the frame  1110  is coupled with the base  104  of the apparatus. However, this may be other way around. I.e. frame  1110  may be coupled with the surface  102  and the first permanent magnet arrangement with the base  104 . 
     As shown in  FIGS. 11, 12, and 13 , the shape of the frame  1110  may differ. For example, it may simply be a plane or plate as shown in  FIGS. 12 and 13 , or provide a cavity for the second permanent magnet  120  and/or the coil  122  as shown in  FIG. 11 . In both cases, the second force may be caused by magnetic interaction between the first permanent magnet  110  and the frame  1110 . I.e. this may happen on areas which are not covered by the second permanent magnets  120 . For example, the magnetic interaction may happen via the coil  122  even though no input signal is provided into the coil  122 . For example, the parts of the frame  1110  extending over the edge of the second permanent magnet  120  may be magnetized with same polarity as the pole of the second permanent magnet  120  that is attached to the frame  1110 . 
     According to an embodiment, the coil  122  is situated between said one or more portion of the frame  1110  that extends over the edge area of the second permanent magnet  120  at least in one direction and the first permanent magnet arrangement. This can be seen, for example, in  FIGS. 11, 12, and 13 . 
     In an embodiment, same polarities of the first and second permanent magnets  110 ,  120  are arranged to face each other. So, for example, north or south polarities may face each other, thus generating force that pushes the surface  102  away from the base  104 . So, for example, if south poles are arranged to face each other, the second permanent magnet  120  magnetizes the frame  1110  with north polarity. Thus, magnetic interaction between said one or more portions of the frame  1110  and the first permanent magnet arrangement may cause pulling force (i.e. surface is pulled towards the base  104 ). This, as explained, may provide balancing force to the first force. However, the first and second forces are not necessarily of equal magnitude. In an embodiment, the first and second forces are substantially of equal magnitude. 
     Still referring to  FIGS. 11, 12, and 13 , in an embodiment, a surface area of a surface of the first permanent magnet  110  that faces the second permanent magnet  120  is greater than a surface area of a surface of the second permanent magnet  120  that faces the first permanent magnet  110 . Further examples of these may be seen in  FIGS. 15 and 16  in which circular magnets  110 ,  120  are used. However, it is equally possible to use magnets of some other shape. Using this approach, enables the second force to be caused by the interaction between the first permanent magnet  110  and the frame  1110 , as they may be directly facing each other at least on some portions. The coil  122  may be arranged between the first permanent magnet  110  and the frame  1110 , which may further enhance the coil&#39;s  122  ability to cause the surface  102  to vibrate. 
     In an embodiment, the second force is caused at least by magnetic interaction between the first permanent magnet  110  and said one or more portion of the frame  1110 . Examples in  FIGS. 11, 12, and 13 , for example. 
     In an embodiment, the coil  122  is situated directly between said one or more portion of the frame  1110  and the first permanent magnet  110 . Again, examples may be seen in  FIGS. 11, 12, and 13 . 
       FIG. 14  illustrates an embodiment. Referring to  FIG. 14 , the first permanent magnet arrangement further comprises a third permanent magnet  1410  configured to face said one or more portion of the frame  1110  (i.e. the portion(s) that extend over the edge area of the second permanent magnet  120 ) in order to generate the magnetic interaction between said one or more portion of the frame  1110  and the first permanent magnet arrangement. 
     In an embodiment, the third permanent magnet  1410  is configured to encircle the first permanent magnet  110 . For example, thus the third magnet  1410  may be a permanent ring magnet. 
     It is further possible that the third permanent magnet  1410  magnetically interacts directly with the second permanent magnet  120 . Thus, for example, this may generate a further pulling force or increase magnitude of the second force. 
     Hence, for example, the first permanent magnet arrangement may comprise two permanent magnets  110 ,  1410  with opposing magnetic polarizations and an iron cup (e.g. frame  1120 ) all coupled together. The second permanent magnet  120  may generate a repulsing force (i.e. first force) with the first permanent magnet  110 , and attractive force with the third magnet  1410  (i.e. second force). 
     For example, magnets and iron cup (frame  1110  and/or  1120  may also be referred to as iron cups) dimensions and materials are selected in such a way that these repulsing and attracting forces compensate each other at the designed center position in up-down direction when there is no electrical input signal in the coil  122  (e.g. speech coil). Electrical input signal creates additional force on surface. This force can be repulsive or attractive depending on the direction of the current, thus alternating current in the coil  122  makes surface part vibrating in up-down direction according to electrical input signal. 
     In the example embodiment of  FIG. 14 , the first permanent magnet  110  does not necessarily have substantial magnetic interaction with the frame  1110 . Hence, the second force may be cause by interaction between the third and second permanent magnets  1410 ,  120  and possibly between the one or more portion of the frame  1110  and the third permanent magnet  1410 . 
     In an embodiment, the frame comprises a cavity for the coil  122  and the second permanent magnet  130 . Example of this may be seen in  FIG. 11 , for example. 
     In an embodiment, the first permanent magnet arrangement comprises a second frame  1120  comprising magnetic material, the second frame  1120  configured to be magnetized by one or more permanent magnets (e.g.  110 ) of the first permanent magnet arrangement in order to increase the second force caused by the magnetic interaction between the first permanent magnet arrangement and said one or more portions of the frame  1110  coupled with the second permanent magnet  120 . Examples of this can be seen in  FIGS. 11, 12, and 14 . As shown in  FIG. 13 , the use of the second frame  1120  may not be necessary. However, using the second frame  1120 , may further enhance the configurability of the second force, for example. 
     As indicated above,  FIGS. 15 and 16  may illustrate some embodiments showing circular second permanent magnet  120  at one part of the arrangement  100  and circular first permanent magnet  110  at the other part of the arrangement  100 . Similarly, coil  122  and frame  1110  are shown. Further, if the second frame  1120  is used, it may be disposed as illustrated in  FIG. 16 . Hence, for example, the second frame  1120  may provide a cavity for receiving/housing the first permanent magnet  110  such that it may be visible at least on one side. Similar housing may be arranged, by using the first frame  1110 , for the second permanent magnet  120  and the coil  122 . 
     Even though the invention has been described above with reference to an example according to the accompanying drawings, it is clear that the invention is not restricted thereto but can be modified in several ways within the scope of the appended claims. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment. It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.