Packaging for an electro-mechanical device comprising an array of moving elements

Abstract

There are provided devices comprising an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a layer on which at least part of the electro- mechanical device is mounted and a cover, wherein the devices enables reducing or cancelling the interferences with the sound waves generated by the electro-mechanical device. Manufacturing methods of the devices are also provided.

Description

[0001] PACKAGING FOR AN ELECTRO MECHANICAL DEVICE COMPRISING AN ARRAY OF MOVING ELEMENTS

[0002] FIELD OF THE INVENTION

[0003] The present invention relates generally to the field of electro-mechanical actuators, also called microelectromechanical systems (MEMS). In particular, it relates to the field of digital sound reconstruction (DSR) speakers.

[0004] BACKGROUND

[0005] References considered to be relevant as background to the presently disclosed subject matter (acknowledgement of these references herein is not to be inferred as meaning that they are in any way relevant to the patentability of the presently disclosed subject matter) include US 8,085,964, US 8,457,338, US 8,126,163, EP 2158787, US 8,374,056, US 8,755,556, US 8,780,673, US 9,391,541, US 9,986,343, US 10,503,136, US 9,654,890, US 9,880,533, US 9,510,103, US 8,994,126, US 9,497,526, US 9,445,170, US 10,520,601, US 10,554,166, US 10,433,067, PCT / IL2023 / 051286, WO2010 / 122556, United States Provisional Patent Application No. 63 / 664,508, United States Provisional Patent Application No. 63 / 649,798 and United States Provisional Patent Application No. 63 / 649,787.

[0006] All these references are of the Applicant, and their content is incorporated herein by reference in their entirety.

[0007] GENERAL DESCRIPTION

[0008] There are provided systems and methods as provided in the appended claims and in the specification.

[0009] In accordance with certain aspects of the presently disclosed subject matter, there is provided a device comprising an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a layer on which at least part of the electromechanical device is mounted, and a cover, wherein one or more cavities of the device opened to outer space of the device have a lowest resonance frequency which is equal to or larger than 14KHz.

[0010] In addition to the above features, the device according to this aspect of the presently disclosed subject matter can optionally comprise one or more of features (i) to (xxviii) below, in any technically possible combination or permutation: i. any cavity of the device opened to the outer space of the device, has a lowest resonance frequency which is equal to or higher than 14KHz; ii. the one or more cavities have a lowest resonance frequency which is equal to or larger than a value between 18 KHz and 20KHz; iii. the cover includes a sound-transparent film protecting the electromechanical device; iv. the cover comprises a plurality of side walls, and a portion located above the electro-mechanical device, the one or more cavities include a first cavity located between a first side wall of the plurality of side walls of the cover, and a first side wall of the electro-mechanical device, wherein a transition between a volume located between the electro-mechanical device and the portion of the cover, and said first cavity, does not include a neck portion; v. the one or more cavities include a second cavity located between a second side wall of the plurality of side walls of the cover, and a second side wall of the electro-mechanical device, wherein the second cavity has a lowest resonance frequency which is equal to or larger than 14KHz; vi. the cover comprises a portion located above the electro-mechanical device, wherein a transition between the volume located between the electromechanical device and the portion, and said second cavity, does not include a neck portion; vii. the device comprises a controller located on the layer, electrically connected to the electro-mechanical device, wherein the electro-mechanical device is separated from the controller by a barrier located on the layer; viii. the barrier corresponds to a material deposited on the layer, separating the electro-mechanical device from the controller; ix. the barrier corresponds to an additional wall of the cover, separating the electro-mechanical device from the controller; x. the device further comprises a controller, wherein the electro-mechanical device is located on a first side of the layer, and the controller is located on a second side of the layer, opposite to the first side; xi. the electro-mechanical device comprises a first set of pads or pins, the controller comprises a second set of pads or pins, a position of the first set of pads or pins matches a position of the second set of pads or pins in a plane parallel to the layer; xii. the first set of pads or pins is electrically connected to the second set of pads or pins by vias going through the layer; xiii. the one or more cavities include a cavity located around the controller; xiv. the device comprises a plurality of electro-mechanical devices, each of them operative to generate sound waves, each of them comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a plurality of controllers, wherein each given electro-mechanical device of the plurality of electro-mechanical devices is electrically connected to a given controller of the plurality of controllers, wherein the plurality of electro-mechanical devices is located on a first side of the layer, and the plurality of controllers is located on a second side of the layer, opposite to the first side; xv. each electro-mechanical device of the plurality of electro-mechanical devices comprises a first set of pads or pins, each controller of the plurality of controllers comprises a second set of pads or pins, the position of the first set of pads or pins of said each given electro-mechanical device matches a position of the second set of pads or pins of said given controller, in a plane parallel to the layer; xvi. a distance between an upper surface of the electro-mechanical device and the cover is below 1mm; xvii. the cover comprises a plurality of side walls, wherein at least one side wall of the plurality of side walls of the cover has a surface operative to reflect at least part of said sound waves, wherein said surface is tilted with respect to a vertical axis, or with respect to an axis orthogonal to the layer; and xviii. the cover comprises a plurality of side walls, wherein at least one side wall of the plurality of side walls of the cover has a surface operative to reflect at least part of said sound waves, wherein said surface comprises a plurality of protruding portions, wherein each protruding portion comprises two surfaces operative to reflect at least part of said sound waves towards a different direction.

[0011] In addition to the above features, the device according to this aspect of the presently disclosed subject matter can optionally comprise one or more of features (xix) to (xliv) below, in any technically possible combination or permutation:

[0012] In accordance with other aspects of the presently disclosed subject matter, there is provided a device comprising an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a controller electrically connected to the electromechanical device, a layer on which the electro-mechanical device and the controller are mounted, a cover comprising a plurality of side walls surrounding the electromechanical device and the controller, wherein the electro-mechanical device is separated from the controller by a barrier located on the layer.

[0013] In addition to the above features, the device according to this aspect of the presently disclosed subject matter can optionally comprise one or more of features (xix) to (xxxii) below, in any technically possible combination or permutation: xix. the barrier prevents communication between a cavity or a volume located between the electro-mechanical device and the cover, and a cavity located between the controller and the cover; xx. the barrier corresponds to a material deposited on the layer, separating the electro-mechanical device from the controller; xxi. the material comprises an epoxy; xxii. the material comprises glob top; xxiii. the material is further located between an upper surface of the controller and the cover; xxiv. the material is further located between a side wall of the controller, and a side wall of the plurality of side walls of the cover; xxv. at least part of the material extends from the layer up to a protruding part of the cover configured to cooperate with a sound-transparent film of the cover, protecting the electro-mechanical device; xxvi. at least part of the material extends from the layer up to the cover, or up to a sound-transparent film of the cover, and protects the electro-mechanical device; xxvii. the barrier corresponds to an additional wall which is part of the cover, wherein the additional wall separates the electro-mechanical device from the controller; xxviii. the device comprises a material located between a side wall of the electromechanical device and a side wall of the plurality of side walls of the cover; xxix. the material prevents air communication between a cavity or a volume located between the electro-mechanical device and a portion of the cover, and a cavity located between the material and a side wall of the plurality of side walls of the cover; xxx. at least part of the material extends from the layer up to a protruding part of the cover configured to cooperate with a sound-transparent film of the cover, protecting the electro-mechanical device; xxxi. the material fills all or a majority of a cavity located between a side wall of the electro-mechanical device, located opposite to a side wall of the electromechanical device facing the controller, and a side wall of the cover; and xxxii. the device comprises a material surrounding four side walls of the electromechanical device, wherein the barrier corresponds to part of said material located between the electro-mechanical device and the controller.

[0014] In addition to the above features, the device according to this aspect of the presently disclosed subject matter can optionally comprise one or more of features listed below, and one or more features (i) to (xviii) and (xxxiii) to (xliv), in any technically possible combination or permutation.

[0015] In accordance with other aspects of the presently disclosed subject matter, there is provided a device comprising an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a controller electrically connected to the electro-mechanical device, a layer, and a cover, wherein the electro-mechanical device is located on a first side of the layer, and the controller is located on a second side of the layer, opposite to the first side, wherein the electro-mechanical device is electrically connected to the controller. In addition to the above features, the device according to this aspect of the presently disclosed subject matter can optionally comprise one or more of features (xxxiii) to (xxxvii) below, in any technically possible combination or permutation: xxxiii. the electro-mechanical device comprises a first set of pads or pins and the controller comprises a second set of pads or pins, wherein a position of the first set of pads or pins matches a position of the second set of pads or pins in a plane parallel to the layer; xxxiv. the first set of pads or pins is electrically connected to the second set of pads or pins by vias going through the layer; xxxv. a transition between a cavity or a volume located between an upper surface of the electro-mechanical device and the cover, and a cavity located between a side wall of the electro-mechanical device and a side wall of the cover, does not include a neck portion; xxxvi. one or more cavities of the device opened to outer space of the device have a lowest resonance frequency which is equal to or larger than 14KHz; xxxvii. any cavity of the device opened to the outer space of the device, has a lowest resonance frequency which is equal to or higher than 14KHz.

[0016] In addition to the above features, the device according to this aspect of the presently disclosed subject matter can optionally comprise one or more of features listed above or below, and one or more features (i) to (xxxii) and (xxxviii) to (xliv), in any technically possible combination or permutation.

[0017] In accordance with other aspects of the presently disclosed subject matter, there is provided a device comprising an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a layer on which at least part of the electromechanical device is mounted, a cover coupled to the layer, wherein a given cavity is located between an upper surface of the electro-mechanical device and the cover, wherein any cavity of the device opened to this given cavity has a lowest resonance frequency which is equal to or higher than 14KHz or no cavity of the device is opened to said given cavity.

[0018] In addition to the above features, the device according to this aspect of the presently disclosed subject matter can optionally comprise one or more of features listed above or below, and one or more features (i) to (xliv), in any technically possible combination or permutation.

[0019] In accordance with other aspects of the presently disclosed subject matter, there is provided a device comprising an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a layer on which at least part of the electromechanical device is mounted, a cover coupled to the layer, comprising a plurality of side walls, wherein at least one side wall of the plurality of side walls of the cover has a surface operative to reflect at least part of said sound waves, wherein said surface is tilted with respect to a vertical axis, or with respect to an axis orthogonal to the layer.

[0020] In addition to the above features, the device according to this aspect of the presently disclosed subject matter can optionally comprise one or more of features above or below, and one or more features (i) to (xliv), in any technically possible combination or permutation.

[0021] In accordance with other aspects of the presently disclosed subject matter, there is provided a device comprising an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a layer on which at least part of the electromechanical device is mounted, a cover coupled to the layer, wherein the cover comprises a sound-transparent film protecting the electro-mechanical device, wherein a distance between an upper part of the electro-mechanical device and the sound-transparent film is equal to or smaller than 1mm.

[0022] In addition to the above features, the device according to this aspect of the presently disclosed subject matter can optionally comprise one or more of features listed above or below, and one or more features (i) to (xliv), in any technically possible combination or permutation.

[0023] In accordance with other aspects of the presently disclosed subject matter, there is provided an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a layer on which at least part of the electro-mechanical device is mounted, a cover coupled to the layer, comprising a plurality of side walls, wherein at least one side wall of the plurality of side walls of the cover has a surface operative to reflect at least part of said sound waves, wherein said surface comprises a plurality of protruding portions.

[0024] In addition to the above features, the device according to this aspect of the presently disclosed subject matter can optionally comprise one or more of features (xxxviii) to (xxxix) below, in any technically possible combination or permutation: xxxviii. each given protruding portion of the plurality of protruding portions comprises two given surfaces operative to reflect sound waves towards a different direction; xxxix. each given protruding portion of the plurality of protruding portions is associated with a triangular shape in cross-section.

[0025] In addition to the above features, the device according to this aspect of the presently disclosed subject matter can optionally comprise one or more of features listed above or below, and one or more features (i) to (xxxvii) and (xl) to (xliv), in any technically possible combination or permutation.

[0026] In accordance with other aspects of the presently disclosed subject matter, there is provided a device comprising an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a layer on which at least part of the electromechanical device is mounted, a cover coupled to the layer, comprising a plurality of side walls, wherein one or more of the side walls of the cover include one or more elements operative to block relative displacement between the layer and the cover along one or more axes.

[0027] In addition to the above features, the device according to this aspect of the presently disclosed subject matter can optionally comprise one or more of features (xl) to (xliii) below, in any technically possible combination or permutation: xl. at least one element of the one or more elements is located on a side of the layer; xli. at least one element of the one or more elements corresponds to a lip protruding from a side wall of the cover up to a side of the layer; xlii. wherein the one or more elements are operative to block a relative translation between the layer and the cover along one or more axes; and xliii. for at least one side wall of the plurality of side walls, a maximal distance between the electro-mechanical device and said side wall is equal to, or smaller than 1mm.

[0028] In addition to the above features, the device according to this aspect of the presently disclosed subject matter can optionally comprise one or more of features listed above or below, and one or more features (i) to (xxxix) and (xliv), in any technically possible combination or permutation.

[0029] In accordance with other aspects of the presently disclosed subject matter, there is provided a device comprising an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a layer on which at least part of the electromechanical device is mounted, a cover coupled to the layer, comprising a plurality of side walls, wherein the cover comprises four corners, each corner being located between adjacent side walls of the plurality of side walls of the cover, wherein a given corner of the four corners has a different shape than all other corners of the four corners.

[0030] In addition to the above features, the device according to this aspect of the presently disclosed subject matter can optionally comprise feature (xliv) below: xliv. the given corner has a rounded shape, which is different from one or more shapes of all other corners of the four corners, or the given corner has a squared shape, which is different from one or more shapes of all other corners of the four corners, or the given corner has a chamfered shape, which is different from one or more shapes of all other corners of the four corners.

[0031] In accordance with other aspects of the presently disclosed subject matter, there is provided one or more manufacturing methods of the various devices described above.

[0032] In some examples, the method can include manufacturing a device, said manufacturing comprising mounting an electro-mechanical device and a controller on at least one layer and fastening a cover to the at least one layer, wherein the electromechanical device is operative to generate sound waves and comprises an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, wherein one or more cavities of the device opened to outer space of the device have a lowest resonance frequency which is equal to or larger than 14KHz.. The device as described to the various examples can correspond to or be part of a digital sound reconstruction speaker.

[0033] The device as described to the various examples can be configured to generate ultrasonic waves.

[0034] The device as described to the various examples above can be configured to generate ultrasonic waves used to scan space and / or detect objects. In some examples, the device can be used as explained in WO 2016 / 166763, incorporated herein by reference in its entirety.

[0035] According to some examples, the proposed solution enables generation of a physical effect (e.g. sound) which matches more accurately a desired input signal. In particular, the error between the physical effect and the input signal is reduced.

[0036] According to some examples, the proposed solution enables generation of a physical effect (e.g. sound) which contains less noise hearable by the human ear.

[0037] According to some examples, the proposed solution enables generation of a physical effect (e.g. sound) with better quality, in a large bandwidth of frequencies.

[0038] According to some examples, the proposed solution proposes a more compact device.

[0039] According to some examples, the proposed solution reduces or cancels various sound interferences which may be generated by a cover of a digital sound reconstruction speaker.

[0040] BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to understand the disclosure and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

[0042] Fig. 1A is a cross-sectional illustration of an individual actuator element in accordance with certain examples of the presently disclosed subject matter;

[0043] - Fig. IB is a cross-sectional illustration of an individual actuator element in accordance with certain examples of the presently disclosed subject matter;

[0044] - Fig. 2 is a top view of an example of an electro-mechanical device including an array of actuator elements; - Fig. 3 is a schematic representation of an electro-mechanical device including a first array of actuator elements and a second array of actuator elements;

[0045] Fig. 4A is a simplified functional block diagram of an apparatus (such as a digital sound reconstruction speaker) including an electro-mechanical device and a controller;

[0046] Fig. 4B is another simplified functional block diagram of an apparatus (such as a digital sound reconstruction speaker) including an electro-mechanical device and a controller;

[0047] - Fig. 4C is a generalized flow-chart of a method of controlling an electromechanical device including one or more arrays;

[0048] - Fig. 5A is a side view of a device including an electro-mechanical device operative to generate sound waves, and a controller;

[0049] - Fig. 5B illustrates a generalized flow-chart of a method of simulating resonance frequencies of a cavity;

[0050] Fig. 6A is a schematic representation of a Helmholtz resonator;

[0051] Fig. 6B is a schematic representation of thin-walled Helmholtz resonator;

[0052] - Fig. 7 is a side view of another device including an electro-mechanical device operative to generate sound waves, and a controller;

[0053] - Fig. 8 is a top view of another device including an electro-mechanical device operative to generate sound waves, and a controller;

[0054] Fig. 9A is a top view of another device including an electro-mechanical device operative to generate sound waves, and a controller;

[0055] Fig. 9B is a side view of another device including an electro-mechanical device operative to generate sound waves, and a controller;

[0056] - Fig. 9C is a side view of another device including an electro-mechanical device operative to generate sound waves, and a controller;

[0057] Figs. 10A and 10B correspond to a side view of a cover for a device including an electro-mechanical device operative to generate sound waves, and a controller;

[0058] - Fig. 11 is a side view of another device including an electro-mechanical device operative to generate sound waves, and a controller;

[0059] - Fig. 12 is a cross-sectional view of the device of Fig. 11; - Fig. 13 is a side view of another device including a plurality of electromechanical devices operative to generate sound waves, and a plurality of controllers;

[0060] Fig. 14 is a side view of a portion of the device of Fig. 11;

[0061] Fig. 15A is a side view of another device including an electro-mechanical device operative to generate sound waves, and a controller;

[0062] - Fig. 15B is a side view of another device including an electro-mechanical device operative to generate sound waves, and a controller;

[0063] Fig. 16A is a view of a cover including side walls with a tilted surface;

[0064] - Fig. 16B is a side view of the cover of Fig. 16A;

[0065] Fig. 16C is a side view of the cover of Fig. 16A, in which propagation of the sound waves has been depicted;

[0066] - Fig. 16D is a side view of another cover including side walls with a tilted surface;

[0067] Fig. 17A is a side view of another device including an electro-mechanical device operative to generate sound waves, and a controller;

[0068] - Fig. 17B is a side view of another device including an electro-mechanical device operative to generate sound waves, and a controller;

[0069] Fig. 18A is a view of a cover including side walls with protruding portions on their inner surfaces;

[0070] Fig. 18B illustrates sound dispersion performed by the cover of Fig. 18A;

[0071] Fig. 18C is a cross-sectional view of the protruding portions of the cover of Figs. 18A and 18B;

[0072] - Fig. 19 is a side view of another device including an electro-mechanical device operative to generate sound waves, and a cover;

[0073] Figs. 20 and 21 represent schematically different examples of the cover of Fig. 19;

[0074] Fig. 22 is a side view of another device including an electro-mechanical device operative to generate sound waves, and a cover;

[0075] Fig. 23 is a top view of a cover usable to protect an electro-mechanical device operative to generate sound waves; and

[0076] Figs. 24 to 29 illustrate generalized flow-charts of different manufacturing methods. DETAILED DESCRIPTION OF EMBODIMENTS

[0077] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the disclosure. However, it will be understood by those skilled in the art that the presently disclosed subject matter may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to obscure the presently disclosed subject matter.

[0078] The term “bearing” as used herein is intended to include any device which allows constrained relative motion, such as bending motion between parts, e.g., a device which connects a moving element to stationary elements and defines the path of motion and the at-rest position of the moving element.

[0079] A “flexure bearing” or a “flexure” is a type of compliant mechanical bearing which allows motion by bending or twisting. A flexure bearing may comprise a flexible part joining two other parts, and is typically simple, inexpensive, compact, and friction- free. Flexure bearings are typically formed of a material which can be repeatedly flexed without disintegrating.

[0080] A spring is intended to include any suitable elastic member, such as, but not limited to, a spirally coiled strip or wire that recovers its shape after compression, bending, twisting, or stretching.

[0081] Addressing an (i,j)'th actuator element in an array of actuator elements can refer to application of voltage bias between a particular row (row i) and a particular column (column j) of the array of actuator elements.

[0082] ANSYS Inc.'s Glossary of MEMS Terminology states that a “dimple” is defined as follows: “a small feature or bump, typically a raised square on the surface of a MEMS device. Dimples can be used as mechanical stops e.g. to control the touch down in a high aspect ratio device”.

[0083] Attention is drawn to Fig. 1A, which is a schematic representation of an actuator element 100 (also called “pixel” or “audio-pixel”) constructed and operative in accordance with certain examples of the present invention.

[0084] The actuator element 100 includes a moving element 110 (also called membrane, or electrical membrane, or moving membrane) and at least one electrode 120. A voltage can be applied (as explained hereinafter, this voltage can be controlled by one or more controllers) to the moving element 110 and / or to the electrode 120. This generates a voltage bias between the moving element 110 and the electrode 120. The resulting electrostatic force enables a motion of the moving element 110. It is appreciated that the terms membrane and electrode are used in the description to refer to the moving and stationary elements respectively, however, in most practical applications both elements move when subjected to force, e.g. by applying a voltage between them. Typically, the membrane moves more than the electrode in response to said voltage, but this need not be the case.

[0085] The moving element 110 is mechanically connected to stationary portions of the actuator element 100 by means of a bearing 150. The bearing 150 includes e.g. one or more flexures and / or one or more springs.

[0086] The bearing 150 defines an axis 125 along which the moving element 120 can travel (the axis 125 is e.g. orthogonal to the surface of the electrode 120). The bearing 150 defines an at-rest position 151 of the moving element 110.

[0087] When no voltage is applied to electrode 120 and to the moving element 110, the moving element 110 settles at the at-rest position 151.

[0088] In a first extreme position 160 (also called latched position), the moving element 110 is located in the vicinity of the electrode 120. In this first extreme position, the distance (along the axis 125) between the electrode 120 and the moving element 110 reaches a minimum (among all possible positions of the moving element 110). A latching voltage can be applied to the moving element 110 and / or to the electrode 120 to maintain the moving element 110 in this latched position.

[0089] In a second extreme position 161, the moving element 110 is located opposite to the electrode 120. In this second extreme position, the distance (along the axis 125) between the electrode 120 and the moving element 110 reaches a maximum (among all possible positions of the moving element 110).

[0090] In some examples, the actuator element 100 can include one or more mechanical stoppers. A mechanical stopper can be used to prevent the moving element 110 to further move away from the electrode 120. For example, the mechanical stopper (see reference 165 in Fig. 1) can define the second extreme position 161.

[0091] In some examples, the mechanical stopper prevents the moving element 110 from being in direct contact with the electrode 120.

[0092] In some examples, the mechanical stopper can include one or more dimples 166 formed on the surface of the electrode 120. In the side view of Fig. 1A, the electrode 120 is located below the moving element 110 (along the travel axis 125 of the moving element 110). Note that this is not mandatory, and the electrode 120 can be located above the moving element 110.

[0093] Fig. IB describes a variant of the actuator element 100.

[0094] In this variant, the actuator element 100 includes a moving element 110 and two electrodes 120 and 121 disposed on opposite sides of the moving element 110. It is appreciated that the distances between the moving element 110 and each of the electrodes 120 and 121 may or may not be equal.

[0095] If no voltage is applied to electrodes 120 and 121 relative to the moving element 110, the moving element 110 settles at the at-rest position, in-between the top and bottom electrodes.

[0096] In a first extreme position 160, the moving element 110 is located in the vicinity of the bottom electrode 120. In this first extreme position 160, the distance (along the axis 125) between the electrode 120 and the moving element 110 reaches a minimum (among all possible positions of the moving element 110). In the example of Fig. IB, mechanical stoppers 165 define the first extreme position 160 and prevent the moving element 110 from being in contact with the bottom electrode 120.

[0097] In a second extreme position 161, the moving element 110 is located in the vicinity of the top electrode 121. In this second extreme position 161, the distance (along the axis 125) between the top electrode 121 and the moving element 110 reaches a minimum (among all possible positions of the moving element 110).

[0098] The moving elements and the electrode(s) are typically fabricated from an electrically conductive material, such as doped monocrystalline silicon, doped polycrystalline silicon, or aluminum, or at least contain an electrically conductive layer. Bearings are typically fabricated from a material capable of elastic deformation without or with minimal plastic deformation, such as monocrystalline silicon, polycrystalline silicon, or aluminum, such that bearings do not retain any permanent deformation in the absence of electrostatic forces, and moving elements always return to the exact same at-rest position when no electrostatic force is applied.

[0099] Attention is now drawn to Fig. 2.

[0100] Fig. 2 depicts an embodiment of an electro-mechanical device 200. The electromechanical device 200 is a MEMS (Micro-Electrical Mechanical System) or a NEMS (Nano-Electronical Mechanical System). As explained hereinafter, the electro-mechanical device 200 can be part of a digital sound reconstruction speaker. As explained hereinafter, the electro-mechanical device 200 can be controlled by one or more controllers in order to generate a sound which complies with an input signal.

[0101] The electro-mechanical device 200 includes an array 201 of a plurality of actuator elements 205. Each of the first actuator elements 205 includes a moving element 110 and at least one electrode 120, as depicted with reference to Fig. 1A.

[0102] Note that in some examples, each of the first actuator elements 205 can include a moving element 110 and two opposite electrodes 120, 121 as described with reference to Fig. IB.

[0103] The actuator elements 205 are arranged along NRI rows and Nci columns of the first array, with NRI>1, NCI>1, wherein NRI and / or Nci is equal to or larger than 2. In some examples, the array is a single row array with multiple actuator elements arranged along a plurality of columns, and in other examples the array is a single column array with multiple actuator elements arranged along a plurality of rows. In some examples, the number of rows is equal to the number of columns, but this is not mandatory.

[0104] The number of rows and columns can be selected depending on various factors, such as the application, the required resolution, manufacturing costs, size of the device, etc.

[0105] The array 201 includes electrical connections 207, 208. The electrical connections 207, 208 can include electrical wires.

[0106] In the example of Fig. 2, the electrical connections 207, 208 are arranged such that all moving elements 110 of the actuator elements 205 belonging to a same row of the array 201 are electrically connected (see electrical connections 208), and all electrodes of the actuator elements 205 belonging to a same column of the array 201 are electrically connected (see electrical connections 207). Note that this is not limitative, and the moving elements of the actuator elements belonging to the same column may be electrically connected along the same column, while the electrodes belonging to the same row may be electrically connected along the same row.

[0107] In the configuration of Fig. 2, Nci first electrical connections 207 and NRI first electrical connections 208 are used.

[0108] As a consequence, when an electrical voltage is applied to a given electrical connection 208 (using one or more controllers not represented in Fig. 2), all the moving elements 110 electrically connected to this given electrical connection 208 receive this electrical voltage.

[0109] Similarly, when an electrical voltage is applied to a given electrical connection 207 (using one or more controllers not represented in Fig. 2), all the electrodes 120 electrically connected to this given electrical connection 207 receive this electrical voltage.

[0110] Attention is now drawn to Fig. 3.

[0111] Fig. 3 depicts another example of an electro-mechanical device 350. The electro-mechanical device 350 is a MEMS (Micro-Electrical Mechanical System) or a NEMS (Nano- Electronical Mechanical System).

[0112] The electro-mechanical device can be part of a digital sound reconstruction speaker. As explained hereinafter, the electro-mechanical device can be controlled by one or more controllers in order to generate a sound which complies with an input signal.

[0113] The electro-mechanical device 350 includes a first array 330 of actuator elements (each including a moving membrane, and one or more electrodes, as explained with reference to Figs. 1A and IB), and a second array 331 of actuator elements (each including a moving membrane, and one or more electrodes, as explained with reference to Figs. 1A and IB). In some embodiments, the electro-mechanical device 350 can include more than two arrays. The first array and the second array can be located on different substrates, or on the same substrate.

[0114] Attention is now drawn to Figs. 4A, 4B and 4C.

[0115] In order to control the electro-mechanical device 200, at least one controller 400 can be used (or a plurality of controllers), operatively coupled to the array 201 of the electro-mechanical device 200.

[0116] Similarly, in order to control an electro-mechanical device (see e.g. reference 350) comprising a first array and a second array, at least one controller 400 can be used (or a plurality of controllers), operatively coupled to the first array 330 and the second array 331 of the electro-mechanical device.

[0117] The one or more controllers 400 can be part of the electro-mechanical device or can be external to it. Note that, in a typical example, the number of first actuator elements is different from the number of second actuator elements. This is however not limitative. The one or more controllers 400 can include one or more processing circuitries, including one or more processors and one or more memories.

[0118] In particular, the one or more controllers 400 can include a hardware-based electronic device with a data processing circuitry (e.g., digital signal processor (DSP), a GPU, a TPU, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), microcontroller, microprocessor etc.). The data processing circuitry (designated also as processing circuitry) can comprise, for example, one or more processors operatively connected to one or more memories, loaded with executable instructions for executing operations, as further described below. The data processing circuitry encompasses a single processor or multiple processors. The one or more processors can represent one or more general-purpose processing devices such as a microprocessor, a central processing unit, or the like. More particularly, a given processor may be one of a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a processor implementing other instruction sets, or a processor implementing a combination of instruction sets. The one or more processors may also be one or more special-purpose processing devices such as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), a network processor, or the like. The one or more processors are configured to execute instructions for performing the operations and steps discussed herein.

[0119] The one or more controllers 400 can receive an input signal 410 (operation 450). The one or more controllers 400 may incorporate an industry standard interface to receive the digital input signal, such as but not limited to an I2S, AC’97, HDA, or SLIMbus interface.

[0120] The input signal 410 can be sampled periodically, according to a sampling clock (a sampler, not represented, can be used to sample the input signal 410). The input signal 410 is informative of the desired physical effect which has to be produced by the electro-mechanical device.

[0121] In some examples, the input signal 410 is informative of a desired sound to be produced by the electro-mechanical device. In this case, the electro-mechanical device is part of a digital sound reconstruction system (DSR). Note that the electro-mechanical device can be used in different systems. For example, in some embodiments, it can be used in a detection system. For example, the detection system may enable sonar applications (for example, for mapping the surrounding space or gesture input).

[0122] In some embodiments, the amplitude of the input signal 410 can correspond to the desired sound intensity (sound pressure level). In some embodiments, the frequency of the input signal 410 can correspond to the pitch of the desired sound.

[0123] The one or more controllers 400 can control the position of each moving element in the array (in case of multiple arrays, in each given array of the multiple arrays) as a function of the digital input signal sampled in accordance with a sampling clock.

[0124] The one or more controllers 400 can use the sampled input signal 410 to determine (operation 455) the number of moving elements of the array to be moved. The number of moving elements can be selected to match (as much as possible), at each time clock, the value of the sampled input signal.

[0125] In case of multiple arrays, operation 455 can include determining a first number of moving elements of the first actuator elements of the first array that need to be moved, and / or a second number of moving elements of the second actuator elements of the second array that need to be moved (operations 455). Note that more than two arrays can be used.

[0126] The array is then controlled accordingly at operation 470 (in case of multiple arrays, at least the first array and the second array are then controlled accordingly).

[0127] Control of the motion of the moving elements of the array(s) can include, e.g., moving a moving element from its at-rest position to an extreme position at which it is latched in close proximity to the electrode. This can include releasing a moving element from its extreme position (latched position) in order to let the moving element reach its at-rest position.

[0128] For example, the one or more controllers 400 may latch or release individual moving elements, such that the number of latched moving elements always equals the number represented by the last (most recently received) data word of the digital input signal received by the one or more controllers 400.

[0129] Alternatively, the algorithm used by the one or more controllers 400 may be such that the number of unlatched moving elements equals the last data word received.

[0130] Latching of a moving element corresponds to a state in which the moving element is maintained in the vicinity of one of the electrodes (this corresponds to an extremal position on the axis on which the moving element is able to move). Unlatching of a moving element corresponds to a state in which the moving element is moved from its latched position (e.g., in the vicinity of the bottom electrode or of the top electrode) to a central position, or to another latched position (e.g., in the vicinity of the top electrode or of the bottom electrode).

[0131] In some embodiments, the one or more controllers 400 generate one or more voltages which are transmitted to a high voltage driver (not represented), which converts low voltages generated by the one or more controllers 400 into higher voltages adapted to drive the actuator elements of the one or more arrays.

[0132] The high voltage driver may, for example, have an amplifier or voltage level shifting functionality allowing relatively high voltages, such as some tens of volts, to be applied between the electrode and the moving element 110 under the control of low- voltage signals transmitted from the one or more controllers 400.

[0133] The high voltage driver may be part of the controller(s) 400.

[0134] The device of Figs. 5A, 7, 8, 9A, 9B, 9C, 10A, 10B, 11, 12 to 14, 15A, 15B, 16A to 16D, 17A, 17B, 19, and 22 can be part of a digital sound reconstruction (DSR) speaker, or can correspond to a digital sound reconstruction (DSR) speaker, with its packaging enabling protecting components thereof.

[0135] Various examples of devices are described hereinafter. In at least some of these examples, one or more cavities of the device that are opened to the outer space of the device (that is to say that there is at least one opening letting acoustic waves propagating from the one or more cavities towards the outer space) have a lowest resonance frequency (also called lowest acoustic resonance frequency or first acoustic mode) which is equal to or above 14KHz (note that a different threshold can be used, as explained hereinafter, depending on the usage of the device). In some examples any cavity of the device that is opened to the outer space of the device have a lowest resonance frequency which is equal to or above 14KHz. This enables reducing or cancelling parasitic sound waves that can be generated by the excitation of the cavities by the sound waves generated by the device. Sound reconstruction is therefore improved. In acoustics, a cavity (also called sound cavity or acoustic cavity) confines the propagation of sound waves within a certain geometry. It is associated with one or more boundaries constraining the propagation of sound waves.

[0136] Attention is now drawn to Fig. 5A, which depicts a device 500.

[0137] In this example, the device 500 includes an electro-mechanical device 510 enabling generating sound. This electro-mechanical device 510 can correspond to, or include e.g., the electro-mechanical device 200 or 350, and is operative to generate sound waves. This electro-mechanical device can also correspond to one or more of the electro-mechanical devices described in the patents and / or patent applications cited in the background section.

[0138] The device 500 further includes a controller 520. As mentioned above, the controller 520 is operative to control operation of the actuator elements of the electromechanical device 510, in order to generate sound. In some examples, the controller 520 can include a high-voltage driver, as already mentioned above.

[0139] The electro-mechanical device 510 and the controller 520 are mounted on a layer 530. The layer 530 can correspond e.g., to a printed circuit board (PCB), a ceramic or glass substrate. This is however not limitative.

[0140] The device 500 further includes a cover 540, coupled to the layer 530 (e.g., by an adhesive, such as glue). The cover 540 includes a plurality of side walls (four side walls - two of them 550, 560 are visible in Fig. 5A), and an upper part 570 located above the side walls.

[0141] In some examples, the upper part 570 of the cover 540 includes at least two protruding lips 581, 582 (protruding horizontally, parallel to the layer 530) enabling reception of a sound-transparent film 580 protecting the electro-mechanical device 510. The sound-transparent film 580 can be as described in WO2010 / 122556. Note that the cover 540 can include four protruding lips, one for each side of the electro-mechanical device 510. The sound-transparent film 580 can be affixed to the protruding lips, using e.g., an adhesive, ultrasonic soldering, mold-over etc.

[0142] In this example, there is an air volume 585 located between the upper part of the electro-mechanical device 510 and the sound-transparent film 580.

[0143] There is an air cavity 565 located between the upper part of the controller 520 and the cover 540.

[0144] There is also an air cavity 585 above the upper part of the electro-mechanical device 510.

[0145] An additional air cavity 586 is present between a side wall of the electromechanical device 510 and the side wall 550 of the cover 540. Note that three cavities similar to the air cavity 586 can be present between respective side walls of the electromechanical device 510 and respective side walls of the cover 540.

[0146] At the interface between the air volume 585 and the air cavity 565, a narrow portion 584 (also called neck or bottleneck) is present, between the protruding lip 581 of the cover 540 and an edge 583 of the electro-mechanical device 510. Indeed, the width 513 of the narrow portion 584 is smaller than the width 514 of the air volume 585 and the width 515 of the air cavity 565, thereby generating the presence of a neck.

[0147] The presence of the neck portion 584, followed by the air cavity 565, induces the creation of an acoustic resonator, which can be modelled as a Helmholtz resonator. This resonator is excited by the sound waves generated by the electro-mechanical device 510 and can generate, in turn, sound waves in the audible range. This can affect the sound reconstruction performance of the digital sound reconstruction speaker.

[0148] Similarly, at the interface between the air volume 585 and the air cavity 586, a narrow portion 588 (also called neck or bottleneck) is present, between the lip 582 of the cover 540 and an edge 589 of the electro-mechanical device 510.

[0149] The presence of the neck portion 588, followed by the air cavity 586, induces the creation of an acoustic resonator, which can be modelled as a Helmholtz resonator. This resonator is excited by the sound waves generated by the electro-mechanical device 510 and can generate, in turn, sound waves in the audible range. This parasitic sound can interfere with and affect the sound reconstruction performance of the digital sound reconstruction speaker.

[0150] Fig. 6A illustrates the principle of a Helmholtz resonator 600.

[0151] The Helmholtz resonator 600 includes a neck (narrow portion) 605 followed by an air cavity 606.

[0152] When excited by an acoustical wave, the Helmholtz resonator 600 resonates at a resonance frequency f0(first mode - corresponding to the smallest resonance frequency of the resonator), as defined by the following formula:

[0153] Equation 1

[0154] In this formula, c is the speed of sound, A is the cross-sectional area of the neck 605 (see reference 607), V is the volume of air inside the cavity 606, and LTotis the total length of the neck 605 (see reference 608).

[0155] Fig. 6B illustrates the principle of a thin-walled Helmholtz resonator 660, including a neck 670 with a negligible length (see https: / / euphonics.org / 4-2-l-the- helmholtz-resonator / , incorporated herein by reference in its entirety). When excited by an acoustical wave, the Helmholtz resonator 660 resonates at a resonance frequency f0(first mode - corresponding to the smallest resonance frequency of the resonator), as defined by the following formula:

[0156] Equation 2

[0157] In Equation 2, A is the area of the opening 670, V is the volume of air inside the cavity 675, and R is the radius of the opening 670.

[0158] In some examples, the neck portion 584, followed by the air cavity 565, can be modelled by the equations of a thin- walled Helmholtz resonator (see Equation 2). Similarly, the neck portion 588, followed by the air cavity 586, can be modelled by the equations of a thin-walled Helmholtz resonator (see Equation 2).

[0159] Note that in the configuration of Fig. 5A, the opening is not circular.

[0160] In some examples, in a first approximation, a dimension such as the width of the neck can be used to approximate R in Equation 2. The parameters defining the resonance frequency (see Equation 2) can be used to select the resonance frequency of the cavity 586 and / or of the cavity 585. In particular, it can be selected to be equal to or above a threshold, such as 14KHz.

[0161] In some examples, the resonance frequency of the air cavity 586 and / or of the cavity 585 can be determined using finite element analysis. Note that this method can be used to model the resonance frequency / frequencies of any of the cavities described hereinafter, or of any other cavities.

[0162] In particular, a model of the cavity can be simulated by using FEA (Finite Element Analysis) tools such as Comsol, ANSYS, Abaqus (this list is not limitative). This enables selecting the dimensions of the cavity (such as width, length and height) enabling obtaining a lowest resonance frequency of the cavity equal to or above the desired threshold, such as 14KHz. Simulation of the resonance frequency can include the following steps, as visible in the method of Fig. 5B.

[0163] The method of Fig. 5B includes (operation 590) creating or importing a geometrical model of the cavity in the software (geometry definition). This can be a precise or approximated model of the cavity, depending on the application. Several geometry options are available, depending on context and application and computing resources. In some examples, a 3D model can be generated, which corresponds to a partial or complete representation of the cavity, or alternatively of part or all of the device with of its cavities.

[0164] In some examples, if the cavity has axial symmetry, some tools can simulate the correct behavior if provided with a geometrical 2D model of the rotational body cross section.

[0165] In some examples, for long structures with a consistent cross section and a length greater than any other dimension, some tools can simulate the correct behavior if provided with a model extruded cross section.

[0166] The method of Fig. 5B further includes (operation 591) defining the material properties, such as fluid's (e.g. air) acoustic properties (this includes density and speed of sound) and the mechanical properties of the structure (Young’s modulus (elasticity of the membrane), Poisson's ratio (for 2D or 3D stress-strain relationships), density and thickness).

[0167] The method of Fig. 5B further includes setting (operation 592) the boundary conditions (real- world constraints). Common conditions include rigid walls (no acoustic energy loss), absorbing walls (to mimic sound absorption), clamped membrane (e.g., to simulate the protective cover 580), A volume outside the device defines the maximal outer space in which the simulation of acoustic waves is conducted. This volume can be simulated using techniques such as a perfectly matched layer (PML), an artificial absorbing boundary, or a radiation boundary for regions expected to experience spherical or planar waves. The method of Fig. 5B further includes creating (operation 593) a mesh of finite elements that represent the model. Non-limitative examples of the geometry of the finite elements include e.g., triangular (2D), tetrahedral (3D), quadrilateral (2D), prismatic (3D), polygonal (2D) or polyhedral (3D) meshes. The maximal dimension of each finite element is selected to be shorter than the shortest wavelength I of interest (for example, audible range). A typical value is to select the maximal dimension of each finite element as smaller or equal to 5 (this is not limitative).

[0168] The method of Fig. 5B further includes running (operation 594) the analysis by the software tool (see examples above). This can include using Eigenfrequency analysis or frequency domain study to compute the natural resonance frequencies of the cavity. If necessary, the method of Fig. 5B can further include post-processing (595). This can include visualizing the mode shapes, pressure distributions and how sound pressure levels (SPL) vary across the cavity.

[0169] If necessary, the method of Fig. 5B can include a validation step (596), in which the simulation results of the model are compared with experimental data (if available), to validate the model.

[0170] The model enables determining whether the lowest resonance frequency of the cavity is equal to or above the target threshold (e.g., 14KHz). If this is not the case, the geometrical dimensions (such as height / width / length) of the cavity are modified, and the method is repeated to generate an updated model used to determine the updated lowest resonance frequency (see reference 597). Note that this loop can be performed automatically using a computer, until convergence is obtained.

[0171] The cavity 586 and the cavity 585 are opened to the outer space of the device, since sound waves generated by these cavities can escape the device towards the outer space.

[0172] Based on Equation 2 and / or on a finite element simulation, it is possible to select dimensions of the air cavity 586 and / or of the cavity 585 such that the minimal resonance frequency of the air cavity 586 and / or of the cavity 585 is equal to or larger than 14KHz. Note that the presence of the neck portions may require selecting dimensions for the device which are not optimal for a loudspeaker. Therefore, other implementations of the device are described hereinafter in which the neck portions have been cancelled.

[0173] Attention is now drawn to Fig. 7, which depicts a device 790, corresponding to the device 500 of Fig. 5A which has been modified to reduce or to avoid the presence of interferences that can be generated by the neck portions.

[0174] In particular, the device 790 includes a material 793 deposited on the layer 530. The material 793 separates the electro-mechanical device 510 from the controller 520. In particular, in some examples, this material 793 separates the air cavity 785 (located between the upper part of the electro-mechanical device 510 and a portion of the cover protecting the electro-mechanical device 510, such as a sound-transparent film) from the controller 520.

[0175] This material 793 constitutes a barrier. It generates a wall located between a side wall of the electro-mechanical device 510 and a side wall of the controller 520. In some examples, the height of the barrier is such that it extends between the layer 530 and the cover 540.

[0176] By virtue of the presence of the material 793, which creates a barrier (or a wall) between the electro-mechanical device 510 and the controller 520, the neck portion 584, that was present in the device 500 between the air cavity located above the electromechanical device 510 and the air cavity located above the controller 520, has been cancelled.

[0177] In this example, the height of the material 793 is such that the material 793 extends from the layer 530 up to the cover 540 (in particular up to the bottom part of the cover - in this example up to the bottom part of the lip 781 operative to receive a sound-transparent film - lip 781 is equivalent to the lip 581). This is not limitative.

[0178] In order to cancel the neck portion 584 that was present between two air cavities in the device of 500 of Fig. 5A, it is enough to deposit the material 793 such that it creates a barrier between the electro-mechanical device 510 and the controller 520. This is illustrated in Fig. 8, which is a top view comparing the device 500 (without the material 793) and the device 790 (with the material 793).

[0179] This is also visible in Fig. 9A, in which the height of the material 793 extends from the layer 530 up to the cover 540 (in particular up to the bottom part of the cover - in this example up to the bottom part of the lip 781 operative to receive a sound- transparent film). Note that it is not mandatory that the material be located under the lip 781.

[0180] In some examples, electrical connections (see references 905 and 906 in Fig. 9B) are present between the electro-mechanical device 510 and the layer 530. These electrical connections may be used to connect the electro-mechanical device 510 to the controller 520. The material 793 may be deposited on the side of the electrical connections 905, such that it is not in contact with these electrical connections 905.

[0181] In some examples, the material 793 is not conductive and can partially or fully encapsulate the electrical connections.

[0182] In Fig. 9A, the material 793 separates the air cavity 785 (located between the upper part of the electro-mechanical device 510 and a sound-transparent film protecting the electro-mechanical device 510) from the air cavity 765 (located between the upper part of the controller 520 and the cover 540).

[0183] In some examples (see Fig. 9A), the material 793 prevents any air communication between the air cavity 785 and the air cavity 765. In particular, the air cavity 765 is not opened to the air cavity 785. As a consequence, the air cavity 765 cannot act as an acoustic resonator with respect to the sound waves generated by the electro-mechanical device 510.

[0184] In addition, the air cavity 765 is not opened to the outer space of the device (and therefore cannot communicate with the outer space of the device). As a consequence, it cannot excite sound waves generated by the electro-mechanical device 510 and redirect them towards the outer space.

[0185] In some examples, it is possible to deposit the material 793 such that it fully fills the air cavity 565 that was present in the device 500, between the controller 520 and the cover 540. This option is visible in Fig. 7, in which the material 793 is also located between the upper part of the controller 520 and the cover 540 (see area 791), and between the area 799 of the layer 530 located on the side of the controller 520 (the area 799 is located between the controller 520 and the side wall 560) and the cover 540. Therefore, the air cavity 565 that was present in the device of Fig. 5A is fully (or mostly) filled by the material 793.

[0186] The material 793 can correspond to an epoxy, such as, but not limited to, glob top.

[0187] In some examples, a material 794 (which can be the same as material 793, or different thereof) separates the electro-mechanical device 510 from the side wall 550 of the cover 540 (in particular, from an inner part of the side wall 550).

[0188] In some examples (see Figs. 8 and 9), the material 794 has been deposited so as to fill only part of the air cavity 586 which is located between the electro-mechanical device 510 and the side wall 550 in the device 500. In this case, the material 794 separates the electro-mechanical device 510 from an air cavity 900 located between the material 794 and the side wall 550 of the cover 540. In some examples, the material 794 prevents any communication between the air cavity 785 (located between the upper part of the electro-mechanical device 510 and a sound-transparent film protecting the electro-mechanical device 510) and the air cavity 900. In this example, the air cavity 900 is not opened to the outer space of the device (and therefore cannot communicate with the outer space of the device). The air cavity 900 is a closed cavity.

[0189] In some examples, due to the presence of electrical connections 906 (see Fig. 9B) between the electro-mechanical device 510 and the layer 530, the material 794 is present from a zone located on a side of the electrical connections 906. In some examples, the height of the material 794 is such that it extends between the layer 530 and the cover 540. In this example, the height of the material 794 extends from the layer 530 up to the bottom part of the lip 782 - equivalent to the lip 582.

[0190] By virtue of the presence of the material 794, which creates a barrier (or a wall) between the air cavity 785 and the side wall 550, the neck portion 588 that was present in the device 500 between the two air cavities 585, 586 has been cancelled.

[0191] In some examples (see Fig. 7), the material 794 is deposited so as to fill the whole air cavity 586 that was present in the device 500. In this case, in a horizontal axis located in the plane of the layer, the material 794 is present from the side wall of the electro-mechanical device 510 up to the side wall 550 of the cover 540. In some examples, due to the presence of electrical connections 906 between the electromechanical device 510 and the layer 530, the material 794 is present from a zone located on a side of the electrical connections 906 up to the side wall 550.

[0192] In some examples, the material can be deposited so as to surround the four sides (four side walls) of the electro-mechanical device 510. This is illustrated in Fig. 8. At the side wall of the electro-mechanical device 510 facing the controller 520, the material is a barrier between the electro-mechanical device 510 and the controller 520 (as visible in Figs. 7 to 9). At each of the other side walls of the electro-mechanical device 510, the material is a barrier between the electro-mechanical device 510 and the side wall of the cover 520 facing the side wall of the electro-mechanical device 510. At each of the other side walls of the electro-mechanical device 510, the material can fill the whole cavity (or most of the cavity) between the electro-mechanical device 510 and the side wall of the cover 540 (see for example Fig. 7), or it can be deposited to act as a barrier between the electro-mechanical device 510 and an air cavity located between the material and the side wall of the cover 540 (see for example the material 794 in Fig. 9A). In this case, the air cavity is not opened to the outer space of the device, since it is surrounded on its sides by the material and the side wall of the cover, and above by the cover.

[0193] The material 794 can correspond to an epoxy, such as, but not limited to, glob top.

[0194] Attention is now drawn to Figs. 10A and 10B.

[0195] In this example, the device includes a cover 1540, coupled to the layer 1590, also called substrate (e.g., by an adhesive, such as glue), on which the electromechanical device and the controller are mounted. The cover 1540 includes a plurality of side walls (four side walls - two of them 1550, 1560 are visible in Figs. 10), which surround the electro-mechanical device and the controller.

[0196] The cover 1540 comprises an additional wall 1537 separating the electromechanical device from the controller. In other words, the cover 1540 includes four side walls (external walls), surrounding the electro-mechanical device and the controller, and an internal wall (additional wall 1537), separating the electromechanical device from the controller. The additional wall 1537 joins two opposite walls of the side walls of the cover 1540.

[0197] The height of the additional wall 1537 is such that it extends from the substrate (on which the electro-mechanical device and the controller are mounted) up to the cover.

[0198] In particular, the additional wall prevents any air communication between an air cavity 1585 (located between the upper part of the electro-mechanical device and the cover, or between the upper part of the electro-mechanical device and a sound- transparent film protecting the electro-mechanical device) and an air cavity 1565, located between the upper part of the controller 520 and the cover.

[0199] As a consequence, the neck portion 584 that was present in the device 500 of Fig. 5A between the side cavity and the air cavity above the electro-mechanical device has been cancelled, since there is no communication / opening between the air cavity 1585 and the air cavity 1565.

[0200] In this example, the air cavity 1565 is not opened to the outer space of the device (there is no air communication / no opening between the air cavity 1565 and the outer space of the device), since it is surrounded by the side wall 1560 of the cover, the additional wall 1537 of the cover, and above, by the cover.

[0201] The structure of Figs. 7 to 10 enables obtaining a device in which one or more cavities of the device, or any cavity of the device, which is opened to the outer space of the device (corresponding to the space located outside the device) has a lowest resonance frequency which is equal to or above a target frequency threshold (such as 14KHz). The lowest resonance frequency corresponds to the first mode of resonance of each cavity.

[0202] The device as described in Figs. 7 to 10 is generally designed for a given usage (also called application). For each given usage, there is a requirement on the frequency range in which the sound waves generated by the device. This frequency range is defined by a minimal frequency value (lower limit), and by a maximal frequency value (upper limit). The target frequency threshold can be selected as the maximal frequency value. In some examples, the target frequency threshold can be selected as equal to 14KHz, or any other suitable value between 14KHz and 20KHz. This kind of frequency threshold is adapted to the generation of audible sound for humans (loudspeaker application). For this given usage, the frequency of the sound waves needs to be in the human audible range, which is between 20 Hz and 20 kHz. In practice, it is possible to select the frequency threshold lower than 20KHz since the sensitivity of the human ear to audible sound already drops significantly above 14KHz.

[0203] Note that a cavity may have multiple resonance frequencies, corresponding to different modes or harmonics. The lowest resonance frequency of each cavity opened to the outer space, that is equal to or above 14KHz, corresponds to the lowest resonance frequency (first mode) of the cavity The other resonance frequencies of the cavity (other modes) are, a fortiori, equal to or above 14KHz.

[0204] In other words, the device does not include any cavity opened to the outer space (in communication with the outer space of the device), which has a lowest resonance frequency smaller than 14KHz. Cavities which are not opened to the outer space can have resonance frequencies which are lower than 14 KHz.

[0205] Indeed, in Fig. 7, the air cavities that were located on the sides of the electromechanical device (see 565 and 586 in the device of Fig. 5A - note that two additional side cavities similar to cavity 586 are also present) have been filled by a material. The other cavities, such as the cavity 785 (visible in Figs. 7, 9A and as reference 1585 in Fig. 10B), which is opened to the outer space, has a resonance frequency equal to or above 14KHz. This is due to the dimensions of this cavity (height of the cavity 785, corresponding to the distance between the upper part of the electro-mechanical device 510 and the cover, width 798 of the cavity 785 corresponding to the distance between the lateral boundaries 793 and 794 and length 799 of the cavity 785 corresponding to the distance between the two other lateral boundaries constituted by the material), which dictates the resonance frequency of the cavity, as explained hereinafter (see Equation 3 which can be used herein). These dimensions are selected to obtain a lowest resonance frequency equal to or above 14KHz.

[0206] In some examples, the resonance frequencies of the cavity 785 can be determined by Equation 3:

[0207] Equation 3

[0208] In Equation 3, W corresponds to the width of the cavity, H corresponds to the height of the cavity, and L corresponds to the length of the cavity.

[0209] In Equation 3:

[0210] - m = 0, 1, 2,... for modes across the width W;

[0211] - n = 0, 1, 2,. . . for modes across the height H;

[0212] - p = 0, 1, 2,. . . for modes across the length L;

[0213] - c is the speed of sound in air (343 m.s1).

[0214] For W and H equal to 10mm and L equal to 1mm, the following resonance frequencies are obtained:

[0215] As can be seen in the table, the lowest resonance frequency is equal to 85KHz, which is well above the target frequency threshold. In addition, it can be seen that the parameter p dominates the variation in the resonance frequency.

[0216] Note that the selection of the dimensions of the cavity enabling obtaining the lowest resonance frequency equal to or above the target frequency threshold can be also performed by using finite element analysis, as explained above with reference to Fig. 5B.

[0217] In Fig. 9A, the air cavities 785 and 900 are not in communication with outer space, since they are sealed on all of their sides by the material and the cover.

[0218] In Figs. 10A and 10B, the air cavity 1565 is sealed on all of its sides by the cover, and is therefore not in communication with the outer space of the device. Note that air cavities which are not opened to the outer space of the device may or may not resonate at audible frequencies but these sound waves would be confided to these cavities and would not impact the performance of the sound reconstruction.

[0219] With the design of the device depicted with respect to Figs. 7 to 10, a cavity (see 785) is located between an upper surface of the electro-mechanical device and the cover (in particular, between the upper surface of the electro-mechanical device and the sound-transparent film of the cover). With the design of the device depicted with respect to Figs. 7 to 10, at least one of the following conditions is met: no additional cavity of the device is opened to this cavity 785 (see Figs. 7 to 10 in which the barrier constituted by the material, or by the additional wall of the cover, prevents communication with the cavity 785); any additional cavity of the device opened to this cavity has a resonance frequency which is equal to or higher than a target frequency threshold, such as 14KHz (or any value between 14KHz and 20KHz).

[0220] The various designs mentioned above prevent side cavities opened to outer space from perturbating the sound waves generated by the device in the operational frequency range of the device.

[0221] Ideally, a loudspeaker chip package is designed to exhibit no resonances within the audible frequency range (20 Hz to 20 kHz). However, if resonances are present, it is preferable for them to occur at the upper limits or beyond the audible range. This preference aligns with the known characteristics of the human hearing sensitivity curve, where sensitivity decreases at higher frequencies. Therefore, placing any unavoidable resonances above the most sensitive regions of human hearing minimizes their perceptual impact, ensuring optimal audio performance.

[0222] For a loudspeaker application, the cavities of the device (which are opened to outer space and therefore can generate interferences impinging sound reconstruction performance) are designed with a resonance frequency above a certain target threshold adapted to the usage of the device (e.g. 14KHz).

[0223] In some examples, resonances at lower frequencies may still be acceptable, provided their amplitudes are sufficiently low so as not to interfere with the desired audio output or be perceptible at disruptive levels.

[0224] For other usages of the device, such as the generation of ultrasound frequencies and / or scanning of outer space using ultrasound frequencies and / or usage of the device as a range finder, the target frequency threshold can be selected as higher than 14KHz, such as 30KHz or 40KHz. Therefore, the values mentioned above for the target frequency threshold can differ depending on the usage of the device. This is not limitative.

[0225] Other target frequency thresholds can be used, depending on the usage of the device, and the corresponding operational frequency range of the device, which is bound by an upper limit which can be selected as the target frequency threshold.

[0226] Attention is now drawn to Fig. 11.

[0227] In this example, the device 1100 includes an electro-mechanical device 1110 located on a first side 1101 of a layer 1130 (e.g., PCB). The device 1100 includes a cover 1140 with four side walls, surrounding the electro-mechanical device 1110. Two walls 1150, 1160 of the four side walls are visible in Fig. 11.

[0228] The cover 1140 is fastened to the layer 1130, and, in particular, to the first side 1101 of the layer 1130. The side walls of the cover may be fastened to the first side 1101 of the layer 1130.

[0229] In this example, the controller 1141 is located on a second side 1102 of the layer 1130. The second side 1102 is opposite to the first side 1101.

[0230] Fig. 12 illustrates a possible solution for enabling electrical connections between the electro-mechanical device 1110 and the controller 1141.

[0231] In this example, electrical connectors (e.g., vias 1122) are used to connect the electro-mechanical device 1110, located on the first side 1101 of the layer 1130, to the controller 1141, located on the second side 1102 of the layer 1130. The vias 1122 extend through the layer 1130.

[0232] The electro-mechanical device 1110 includes a first set of pads or pins 1150. The controller 1141 includes a second set of pads or pins 1151. In order to ensure proper electrical connection between the electro-mechanical device 1110 and the controller 1141, the device 1110 is manufactured such that a position of the first set of pads or pins 1150 matches a position of the second set of pads or pins 1155, in a plane parallel to the layer 1130 (see plane X, Y in Fig. 12). Note that this match can include a certain tolerance, as in any manufacturing process.

[0233] The first set of pads or pins 1150 is electrically connected to the second set of pads or pins 1155 by vias 1122 going through the layer 1130. Each respective pad or pin of the first set is connected to a respective pad or the pin of the second set associated with the same position in the X-Y plane. This design reduces the number of electrical connections with respect to other designs in which the controller is located on the side of the electro-mechanical device.

[0234] Attention is now drawn to Fig. 13.

[0235] In the example of Fig. 13, the device 1300 includes a plurality of electromechanical devices 13101, 13102, 13103. The plurality of electro-mechanical devices is located on a first side 1301 of a layer 1330 (e.g., PCB).

[0236] The device 1300 includes a cover 1340 with four side walls, surrounding the plurality of electro-mechanical devices 13101, 13102, 13103. Two walls 1350, 1360 of the four side walls are visible in Fig. 13.

[0237] Note that the number of electro-mechanical devices can be equal to N, with N>2.

[0238] The cover 1340 is fastened to the layer 1330, and in particular, to the first side 1301 of the layer 1330.

[0239] The device 1300 further includes a plurality of controllers 13411, 13412, 13413. Note that the number of controllers can be equal to N, with N>2.

[0240] In this example, the plurality of controllers is located on a second side 1302 of the layer 1330. The second side 1302 is opposite to the first side 1301.

[0241] Each given electro-mechanical device of the plurality of electro-mechanical devices 13101, 13102, 13103 is electrically connected to a given controller of the plurality of controllers 13411, 13412, 13413.

[0242] Each given electro-mechanical device of the plurality of electro-mechanical devices 13101, 13102, 13103 comprises a first set of pads or pins. Each given controller of the plurality of controllers 13411, 13412, 13413 comprises a second set of pads or pins. For each pair including a given electro-mechanical device and a given controller electrically connected to the given electro-mechanical device, the position of the first set of pads or pins of the given electro-mechanical actuator matches a position of the second set of pads or pins of the given controller, in a plane X-Y parallel to the layer 1330. For each pair, the first set of pads or pins is connected to the second set of pads or pins, by the vias 1322. Note that this match can include a certain tolerance, as in any manufacturing process.

[0243] Attention is now drawn to Fig. 14.

[0244] In the example depicted in Fig. 11, an air cavity 1161 is present between the upper part of the electro-mechanical device 1110 and the cover 1140 (or the sound- transparent film 1180 protecting the electro-mechanical device 1110). Another air cavity 1162 is present between a side wall 1163 of the electromechanical device 1110 and the side wall 1160 of the cover 1140.

[0245] As visible in Figs. 11 and 14, the transition between the air cavity 1161 and the air cavity 1162 does not include a neck portion. This is due to the fact that the side wall 1160 does not include a protruding lip for supporting the sound- transparent film 1180. The side wall 1160 includes a first part 1167 (which is a full block, and not a protruding lip), followed by a second part 1168, wherein the first part 1167 is thicker than the second part 1168, and the second part 1168 is higher than the first part 1167. The crosssection of the side wall 1160 therefore corresponds to a step. The sound-transparent film 1180 is supported by the first thick part 1167 and affixed to it.

[0246] One or more of the dimensions of the air cavity 1162 can be selected such that the resonance frequency (first mode - smallest resonance frequency) of the air cavity 1162 is above a target frequency threshold. As mentioned above, the target frequency threshold can correspond to 14KHz, or any suitable value between 14KHz and 20KHz (or other values in case the device is used to generate ultrasonic waves). In other words, the resonance frequency of the air cavity 1162 can be selected to be outside of the audible range. As a consequence, even if sound waves generated by the electromechanical device 1110 excite the air cavity 1162, the resulting sound waves will not affect the performance of the digital sound reconstruction speaker.

[0247] Dimensions of the air cavity 1162 that affect its resonance frequency are the height 1170 of the air cavity 1162 (corresponding to the height of the side wall 1163 of the electro-mechanical device 1110), the width 1171 of the air cavity 1162 (corresponding to the distance 1171 between the side wall 1163 of the electromechanical device 1110 and the inner surface of the side wall 1160 of the cover 1140) and the length of the air cavity. Note that if the inner surface of the side wall 1160 is not straight along the vertical axis, the distance 1171 can be approximated as the average or maximal distance between the side wall 1163 of the electro-mechanical device 1110 and the inner surface of the side wall 1160 of the cover 1140. This is not limitative.

[0248] The lowest resonance frequency (first mode) of the air cavity 1162 can be modelled using Equation 3 above. Note that the selection of the dimensions of the cavity enabling obtaining the lowest resonance frequency equal to or above the target frequency threshold can be also performed by using finite element analysis, as explained above with reference to Fig. 5B. As a consequence, it is possible to select the dimensions of the air cavity 1162 (height 1170, width 1171 and length) such that its lowest resonance frequency is equal to or above 14KHz or 20KHz.

[0249] The principles described above can be used to select the resonance frequency of another air cavity of the device. This is described in Fig. 15A, which illustrates another air cavity 1180 located between a side wall 1102 of the electro-mechanical device 1110 and the side wall 1150 of the cover 1140. In this view, the air cavity 1180 is located on the left side of the device, whereas the air cavity 1162 is located on the right side of the device.

[0250] A dimension of the air cavity 1180 that affects its resonance frequency is the height of the air cavity 1180 (corresponding to the height 1570 of the side wall 1103 of the electro-mechanical device 1110), the width 1571 of the cavity (corresponding to the distance between the side wall 1103 of the electro-mechanical device 1110 and the inner surface of the side wall 1150 of the cover 1140) and the length of the cavity. Equation 3 can be used to model the lowest resonance frequency of the air cavity 1180. Alternatively, finite element analysis can be used, as explained with reference to Fig. 5B.

[0251] Note that if the side wall 1150 is not straight along the vertical axis, the distance 1571 can be selected as the maximal or average distance between the side wall 1103 of the electro-mechanical device 1110 and the inner surface of the side wall 1150 of the cover 1140.

[0252] As a consequence, it is possible to select the dimensions of the air cavity 1180 (height 1570, width 1571 and length) such that its resonance frequency is above 14KHz (or any adapted target frequency threshold).

[0253] In Figs. 14 and 15A, the electro-mechanical device is surrounded by up to four air cavities: each air cavity is located between a side wall of the electro-mechanical device and a side wall of the cover and has a resonance frequency which is above 14KHz (or any adapted target frequency threshold). The four air cavities are in communication and therefore constitute a common cavity. In practice, for calculation purposes, it is possible to model this common cavity by four cavities. This is however not limitative.

[0254] Fig. 15B depicts a device which is a variant of the device of Fig. 15A. In this example, the electro-mechanical device 1110 is located at a first side (upper side) of the 31 layer (substrate) 1185, and the controller is located at a second side (bottom side) of the layer 1185, opposite to the first side.

[0255] In this example, a cavity 1190 has been created at the bottom side of the layer (substrate) 1185. This cavity 1190 surrounds the controller 1141. The cavity 1190 is opened to the outer space of the device. The dimensions (height 1191 of the cavity 1190, width 1192 of the cavity 1190 and length of the cavity) can be selected (based e.g., on Equation 3) such that its lowest resonance frequency is equal to or above 14KHz.

[0256] The principles described above can be used to select the resonance frequency of each cavity, and in particular, of each cavity opened to outer space (such as each cavity located between the electro-mechanical device and a side wall of the cover - up to four air cavities, one per side of the electro-mechanical device).

[0257] In addition, with the structure of Figs. 11 to 15, one or more cavities of the device, or any cavity of the device, which is opened to the outer space of the device (corresponding to the space located outside the device), has a lowest resonance frequency which is equal to or above 14KHz (or any adapted target frequency threshold).

[0258] In other words, the device does not include any cavity opened to the outer space of the device, which has a resonance frequency (smallest resonance frequency of the cavity) which is below 14KHz (or any adapted target frequency threshold).

[0259] Indeed, the cavities located on the sides of the electro-mechanical device (see e.g., 1162 and 1180 - note that up to four different cavities can be present around the electro-mechanical device, one per side of the electro-mechanical device), which communicate with the outer space of the device, have a resonance frequency equal to or above 14KHz (or any adapted target frequency threshold). This is due to the dimensions of these cavities (height, width and length), which dictate the resonance frequency of the cavity, as explained above (see Equation 3).

[0260] Similarly, the dimensions of the air cavity 1161 are selected such that its lowest resonance frequency is above 14KHz, as explained above with reference to the air cavity 785.

[0261] With the design of the device depicted with respect to Figs. 11 to 15, any additional cavity of the device opened to the air cavity 1161 located between an upper surface of the electro-mechanical device and the cover (in particular, between the upper surface of the electro-mechanical device and the sound- transparent film of the cover), has a resonance frequency which is equal to or higher than 14KHz, or any adapted target frequency threshold. The additional cavities include e.g. cavities located between a side wall of the electro-mechanical device and a corresponding side wall of the cover, as explained above.

[0262] The various designs mentioned above prevent cavities opened to outer space from perturbating the sound waves generated by the device in the operational frequency range of the device.

[0263] Attention is now drawn to Figs. 16A to 16D.

[0264] Applicant discovered that the side wall(s) of the cover may act as a reflector, which reflect(s) the sound waves generated by the electro-mechanical device 1110. This can generate constructive and / or destructive interferences. As a consequence, the sound reconstruction performance of the device can be altered.

[0265] As explained in the various examples described in the specification, it is proposed to use a cover which includes side walls. The side walls surround the electromechanical device. In some cases, the side walls also surround the controller.

[0266] As visible in Figs. 16A to 16D, it is proposed to use a cover which includes one or more side walls which have a slope with respect to a vertical axis (or, equivalently, with respect to an axis orthogonal to the plane of the layer on which the electromechanical device is mounted). The slope corresponds to an angle with respect to a vertical axis (or, equivalently, with respect to an axis orthogonal to the plane of the layer on which the electro-mechanical device is mounted) which is larger than 0 degree. There is no maximal value for the angle, as long as it is smaller than 90 degrees. However, in practice, the higher the angle, the higher the dimensions of the device.

[0267] One or more of the side walls of the cover have a surface which has a slope, with respect to the vertical axis (or, equivalently, with respect to an axis orthogonal to the plane of the layer on which the electro-mechanical device is mounted). This feature can be implemented for one, two, three, or four of the side walls of the cover.

[0268] For each side wall which includes this feature, the tilted surface corresponds to the inner surface of the side wall. The inner surface faces a corresponding side wall of the electro-mechanical device (in opposition to the outer surface of the side wall, which faces the space outside of the cover). Note that the features of a side wall of the cover with a slope can be implemented for each of the side walls of the cover, or for at least some of them. In Figs. 16A to 16C, the cover 1600 includes side walls 1610 and 1620. Both side walls 1610, 1620 have a slope. In particular, the side wall 1610 has an inner surface 16101. This inner surface 16101 is the surface of the side wall 1610 that faces the electromechanical device 1680. This inner surface 16101 has an angle 1611 with respect to the vertical axis 1612 (or, equivalently, with respect to an axis orthogonal to the plane of the layer 1681 on which the electro-mechanical device 1680 is mounted).

[0269] The side wall 1620 has an inner surface 16201. This inner surface 16201 is the surface of the side wall 1620 that faces the electro-mechanical device 1680. This inner surface 16201 has an angle 1621 with respect to the vertical axis 1622 (or, equivalently, with respect to an axis orthogonal to the plane of the layer on which the electromechanical device 1680 is mounted).

[0270] As visible in Fig. 16C, even if sound waves 1650 generated by the electromechanical device 1680 impinge the side walls 16101 and / or 16201, they will be reflected outside of the device (see reflected sound waves 1690). As a consequence, the side walls do not generate interferences.

[0271] Fig. 16D illustrates another example, in which two of the side walls of the cover have a surface with an angle (see 1692, 1693) with respect to the vertical axis 1612 (or, equivalently, with respect to an axis orthogonal to the plane of the layer 1681 on which the electro-mechanical device 1680 is mounted) which is equal to around 60 degrees.

[0272] Note that the features of a side wall of the cover with a slope equal to or larger than 45 degrees can be implemented in combination with one or more of the various features described herein or can be implemented without one or more of the various features described herein.

[0273] Attention is now drawn to Figs. 17A and 17B.

[0274] Figs. 17A and 17B propose a solution which can be used to reduce or cancel interferences that can be created by the reflection of sound waves, generated by the electro-mechanical device, by side wall(s) of the cover.

[0275] When the distance 1720 between the upper part 1721 of the electro-mechanical device 1710, and the cover (in particular, the sound-transparent film 1780 located above the electro-mechanical device 1710) is below a threshold, the interferences can be reduced or even cancelled. In some examples, the threshold is equal to 1mm.

[0276] This distance 1720 can be measured along a vertical axis, or with respect to an axis orthogonal to the plane of the layer 1730 on which the electro-mechanical device 1710 is mounted. Note that the features of using a certain maximal distance between the electromechanical device and the cover can be implemented in combination with one or more of the various features described herein or can be implemented without the various features described herein.

[0277] Attention is now drawn to Fig. 18A, which depicts a cover 1840. The cover 1840 is usable to be affixed to a layer on which an electro-mechanical device is mounted, as explained in the various embodiments.

[0278] The cover 1840 includes four side walls, surrounding the electro-mechanical device (and, in some examples, the controller, in case it is located on the same side of the layer as the electro-mechanical device).

[0279] One or more of the side walls are associated with a plurality of protruding portions 18501, 18502, etc. Each protruding portion can be viewed as a tooth protruding from the side wall, towards the electro-mechanical device.

[0280] Each respective protruding portion includes two respective surfaces (also called facets) operative to reflect sound waves generated by the electro-mechanical device towards a different direction. In Fig. 18A, the protruding portion 18501 includes a first surface 18501, i and a second surface 18501,2. The protruding portion 18502 includes a first surface 18502,1 and a second surface 18502,2. For each protruding portion (tooth), a normal (normal vector) to the first surface has a different direction than a normal (normal vector) to the second surface. For each protruding portion, the first surface 18502,1 and the second surface 18502,2 join each other by an edge.

[0281] As a consequence, for each given protruding portion (see e.g., 18501 in Fig. 18C), sound waves propagating along a given direction 1870 are reflected by the first surface (see e.g., 18501, i in Fig. 18C) of the given protruding portion along a first direction 18701, and by the second surface (see e.g., 18501,2 in Fig. 18C) of the given protruding portion along a first direction 18702.

[0282] This architecture of the side walls of the cover enables spreading in the space the energy of the incoming sound waves that impinge the side walls. This enables reducing or cancelling interferences that can be generated by the sound waves reflected by the side walls of the cover.

[0283] In some examples, as visible in Fig. 18C, each protruding portion has a triangular shape in a cross-sectional view. Each respective surface constitutes a side of the triangle. The two surfaces are joined by a vertex 1851. The sharpness of each protruding portion depends on the angle (see e.g., reference 1888) between the respective surfaces (see e.g., references 18501, i, 18501,2). A typical range for this angle can be in the range 10-170 degrees. This is not limitative. Note that the smaller the angle, the sharper the protruding portion, and in turn, the better the split performed by the protruding portion. However, the smaller the angle, the larger the space used by the side walls. A compromise between space and energy split can be performed, depending on the needs. In the illustrated cover, all protruding portions have the same shape and angles but this is not a limitation. If the angles are different, the soundwaves would be scattered into more than 2 directions and would therefore be less impactful at any given direction.

[0284] Attention is now drawn to Fig. 19.

[0285] Assume that the device includes a cover 1940. The cover 1940 can correspond to one or more of the examples described herein. The cover 1940 includes four side walls (three of them are visible in Fig. 19, see references 1950, 1951, and 1952).

[0286] The device 1900 includes an electro-mechanical device 1910 enabling generating sound. This electro-mechanical device 1910 can correspond e.g., to the electro-mechanical device 200 or 350 (or to another electro-mechanical device operative to generate sounds), and is operative to generate sound waves. This electromechanical device 1910 is mounted on a layer 1930 (e.g., PCB).

[0287] The device 1900 can further include a controller (not visible in Fig. 19 - similar to controller 520), which can be either located on the same side of the layer 1930 as the electro-mechanical device 1910, or an opposite side of the layer 1930, as already explained above.

[0288] The side walls of the cover 1940 surround the electro-mechanical device 1910. When the controller is located on the same side of the layer 1930 as the electromechanical device 1910, the side walls of the cover 1940 also surround the controller.

[0289] The cover 1940 is affixed to the layer 1930. This can be achieved by fastening at least part of the side walls of the cover 1940 to the layer 1930, using an adhesive such as glue.

[0290] In some examples, the cover 1940 includes one or more elements 1960 that are operative to block relative displacement between the layer 1930 and the cover 1940 along at least one axis (or along a plurality of axes). The one or more elements 1960 can prevent a relative translation between the cover 1940 and the layer 1930, along one or more axes in the plane of the layer (or parallel to the layer). Assume that the plane of the layer 1930 is defined by two orthogonal axes: a first axis X (orthogonal to two side walls 1950, 1951 of the cover 1940) and a second axis Y (orthogonal to two other side walls of the cover 1940).

[0291] The one or more elements 1960 correspond to stoppers, which prevent relative motion (relative translation) between the cover and the layer, along one or more axes.

[0292] In some examples, one side wall of the cover 1940 is associated with an element 1960 (stopper). In some examples, two side walls of the cover 1940 are each associated with an element 1960 (stopper). In some examples, three side walls of the cover 1940 are each associated with an element 1960 (stopper). In some examples, four side walls of the cover 1940 are each associated with an element 1960 (stopper).

[0293] If two side walls each equipped with an element 1960 correspond to opposite side walls, a relative translation between the cover 1940 and the layer 1930 along an axis orthogonal to the side walls is therefore prevented. In Fig. 19, since two opposite side walls 1950, 1951 of the cover 1940 are equipped with a stopper 1960, a relative translation between the cover 1940 and the layer 1930 is prevented along the X axis. Note that the same can be performed along the Y axis. If the two other opposite side walls of the cover 1940 are equipped with a stopper, a relative translation between the cover 1940 and the layer 1930 is prevented along the Y axis.

[0294] The element 1960 can correspond to a lip protruding, along an axis orthogonal to a plane of the layer, from the side wall of the cover up to a side of the layer (thereby preventing relative motion between the cover and the layer). In some examples, the element 1960 is attached to a side wall of the cover 1940. In some examples, the element 1960 can correspond to an extension of the side wall of the cover 1940, which extends up to the side of the layer.

[0295] The width 2000 of the element 1960 (along the Y axis - see Fig. 20) can be selected depending on the needs. In some examples, it can correspond to at least the majority of the width 2010 of the layer 1930 (along the Y axis - see Fig. 20).

[0296] The height 2020 of the element 1960 (along the Z axis - see Fig. 20) can be selected, depending on the needs. In some examples, it can correspond to at least the majority of the height 2030 of the layer 1930 (along the Y axis - see Fig. 20).

[0297] Note that the element 1960 can have different shapes.

[0298] In some examples (see Fig. 21), the element 1960 can include a set of lips 2100, 2110, 2120 (also called teeth). Consecutive lips of the set are separated by a space (see 2130, 2140). Each lip acts as a stopper preventing relative motion between the cover 1940 and the layer, along one or more axes in the X-Y plane. The number of lips of the element 1960 can be selected depending on the needs (the minimal number being two).

[0299] The plurality of lips extends (along a vertical axis Z, orthogonal to the plane of the layer 1930) from the side wall up to the side of the layer 1930.

[0300] In some other examples, the element 1960 can correspond to a single continuous block extending (along a vertical axis Z, orthogonal to the plane of the layer) from the side wall up to the side of the layer. This is illustrated for example in Fig. 20.

[0301] Since prevention of a relative motion (relative translation) between the cover and the layer has been achieved, it is possible to reduce the distance between the electromechanical device and the side walls of the cover. Indeed, since the risk that the cover will move and damage the electro-mechanical device is now reduced, it is possible to place the cover in close proximity to the electro-mechanical device.

[0302] In some examples (see Fig. 22), for at least one side wall (see side wall 1950) of the cover 1940, the maximal distance 2200 between the electro-mechanical device 1910 (measured from the side wall 1911 of the electro- mechanical device 1910) and this side wall (see side wall 1950) of the cover 1940 is selected to be less than 1mm, such as any number between 0.1mm and 1mm. This is not limitative.

[0303] This distance can be measured along an axis extending in the plane of the layer, such as the axis X (for side walls orthogonal to axis X), or along the axis Y (for side walls orthogonal to axis Y). Equivalently, the distance can be measured along an axis orthogonal to the side wall of the electro-mechanical device or to the side wall of the cover.

[0304] This maximal distance can be used between any side wall of the cover equipped with the element 1960, and the side wall of the electro-mechanical device facing this side wall.

[0305] Selection of the distance (between a side wall of the electro-mechanical device and a corresponding side wall of the cover) below a certain threshold puts the resonance frequency of the cavity located between the side wall of the electro-mechanical device and the side wall of the cover outside of the audible range (e.g., equal to or above 14KHz, or equal to or above any values between 14KHz and 20KHz). Indeed, as visible in Equation 3, reduction of the width of the cavity increases the lowest resonance frequency (fundamental mode / first mode) of the cavity.

[0306] Attention is now drawn to Fig. 23, which depicts a cover 2340. The cover 2340 can be used as explained in the various examples above. In particular, it can be fastened to a layer on which the electro-mechanical device is mounted, in order to cover it. The cover 2340 includes four side walls 2350, 2351, 2352, and 2353.

[0307] In this example, the cover 2340 includes four corners 2360, 2361, 2362, and 2363. Each corner corresponds to the transition between adjacent side walls of the cover.

[0308] In this example, one corner has a shape which is different from the other corners. The other corners may have the same shape - this is however not limitative. This avoids errors when placing the cover during the manufacturing process. In particular, when the cover is fastened to the layer on which the electro-mechanical device is mounted, the presence of a corner with a different shape facilitates correct fastening of the cover to the layer.

[0309] In this example, the cover is associated with three squared corners 2360, 2362, and 2363 and one rounded corner 2361. The squared or rounded shape of each corner can be assessed in a top view of the cover.

[0310] In other examples, the cover is associated with three rounded corners and one squared corner. These examples are not limitative and other shapes can be used.

[0311] In some examples, one corner has a rounded shape, which is different from one or more shapes of all other corners (three corners) of the four corners.

[0312] In some examples, one corner has a squared shape, which is different from one or more shapes of all other corners (three corners) of the four corners.

[0313] In some examples, one corner has a chamfered shape, which is different from one or more shapes of all other corners (three corners) of the four corners.

[0314] Attention is now drawn to Fig. 24, which describes a manufacturing process of a device, such as the device of Figs. 7 to 9.

[0315] The method of Fig. 24 includes mounting (operation 2400) an electromechanical device and a controller on a layer (such as a PCB). Examples of electromechanical devices and controllers have been provided above.

[0316] The method further includes depositing (operation 2410) a material between the electro-mechanical device and the controller, to create a barrier between the electromechanical device and the controller. In order to control the placement of the material on the layer, a dispenser can be used to deposit the material. The material can correspond to an epoxy, such as, but not limited to, glob top. The method further includes fastening (operation 2420) a cover to the layer. The cover includes four side walls surrounding the electro-mechanical device and the controller.

[0317] The method further includes fastening (operation 2430) a sound-transparent film to the cover, which covers the electro-mechanical device.

[0318] Attention is now drawn to Fig. 25, which describes a manufacturing process of a device, such as the device of Fig. 10.

[0319] The method of Fig. 25 includes mounting (operation 2500) an electromechanical device and a controller on a layer (such as a PCB). Examples of electromechanical devices and controllers have been provided above.

[0320] The method of Fig. 25 further includes manufacturing (operation 2510) a cover, including four side walls, and an additional wall joining two of the side walls.

[0321] The method of Fig. 25 further includes fastening (operation 2520) the cover to the layer. The additional wall of the cover creates a separation (barrier) between the electro-mechanical device and the controller.

[0322] Attention is now drawn to Fig. 26, which describes a manufacturing process of a device, such as the device of Figs. 11 to 15.

[0323] The method of Fig. 26 includes mounting (operation 2600) at least one electromechanical device on a first side of a layer (such as a PCB). The electro-mechanical device includes a first set of pads or pins. Examples of electro-mechanical devices have been provided above.

[0324] The method of Fig. 26 further includes mounting (operation 2610) at least one controller on a second side of the layer. The controller includes a second set of pads or pins. The position of the first set of pads or pins is selected to match a position of the second set of pads or pins, in a plane (X-Y) parallel to the layer.

[0325] The method of Fig. 26 further includes electrically connecting (operation 2620) the first set of pads or pins to the second set of pads or pins by vias going through the layer. Each respective pad or pin of the first set is connected to a respective pad or the pin of the second set associated with the same position in the X-Y plane.

[0326] The method of Fig. 26 further includes fastening (operation 2630) a cover to the layer. The cover includes four side walls surrounding the electro-mechanical device.

[0327] Attention is now drawn to Fig. 27, which describes a manufacturing process of a device, such as the device of Figs. 18A to 18C. The method of Fig. 27 includes mounting (operation 2700) an electromechanical device on a layer (such as a PCB). Examples of electro-mechanical devices have been provided above.

[0328] The method of Fig. 27 further includes manufacturing (operation 2710) a cover, including four side walls. At least one of the side walls is manufactured to include a plurality of protruding portions, which protrude from the inner surface of the side wall. Each protruding portion includes two respective surfaces (also called facets). For each protruding portion (tooth), a normal to the first surface has a different direction than a normal to the second surface. Each side wall of the cover can be manufactured to include the plurality of protruding portions.

[0329] The method of Fig. 27 further includes fastening (operation 2730) the cover to the layer. For each side wall including a plurality of protruding portions, the surface including the plurality of protruding portions is oriented towards the electro-mechanical device.

[0330] Attention is now drawn to Fig. 28, which describes a manufacturing process of a device, such as the device of Figs. 19 to 22.

[0331] The method of Fig. 28 includes mounting (operation 2800) an electromechanical device on a layer (such as a PCB). Examples of electro-mechanical devices have been provided above.

[0332] The method of Fig. 28 further includes manufacturing (operation 2810) a cover, including four side walls. At least one of the side walls includes a stopper, which corresponds to an element protruding in a plane of the side wall. In some examples, each side wall includes a stopper.

[0333] The method of Fig. 28 further includes fastening (operation 2820) the cover to the layer. For each side wall including a stopper, the stopper is located on a side of the layer.

[0334] Attention is now drawn to Fig. 29, which describes a manufacturing process of the cover of Fig. 23.

[0335] The method of Fig. 29 includes manufacturing (operation 2900) a cover including four side walls. The cover includes four corners, wherein each corner corresponds to a transition between two adjacent side walls of the cover.

[0336] The method of Fig. 29 includes manufacturing (operation 2910) a given corner of the four corners with a different shape than all other corners of the four corners. For example, the given corner has a rounded shape and the other corners have a squared shape, or the given corner has a squared shape and the other corners have a rounded shape. Any other relevant combination of shapes can be used, which enables differentiating between a specific given corner, and the three other corners.

[0337] The method further includes fastening the cover to a layer on which an electromechanical device is mounted.

[0338] It is possible to combine the various features described in the various examples described above. For example, different types of side walls have been described (with an inclined surface, and / or with protruding portions of their inner surface, and / or with a stopper), which can be used in combination and / or in any of the examples described above.

[0339] Similarly, different types of devices have been described, with different solutions for handling air cavities of the device. The various solutions can be combined in any technical combination. It is possible to use, for a given cavity, a solution described in a given example, and to use, for another cavity, a solution described in another example.

[0340] The various systems and methods can be used to control one or more systems as described in US Provisional Application No. 63 / 649,798 and US Provisional Application No. 63 / 649,787. The contents of these applications are incorporated herein by reference.

[0341] It is to be understood that the invention is not limited in its application to the details set forth in the description contained herein or illustrated in the drawings.

[0342] The invention is capable of other embodiments and of being practiced and carried out in various ways. Hence, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for designing other structures, methods, and systems for carrying out the several purposes of the presently disclosed subject matter.

[0343] Those skilled in the art will readily appreciate that various modifications and changes can be applied to the embodiments of the invention as hereinbefore described without departing from its scope, defined in and by the appended claims.

[0344] It is appreciated that certain functionalities described herein, e.g. moving element control functionalities, may, if desired, be implemented in software. Features of the present invention which are described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, features of the invention, including method steps, which are described for brevity in the context of a single embodiment or in a certain order, may be provided separately or in any suitable sub-combination, or in a different order, "e.g." is used herein in the sense of a specific example which is not intended to be limiting.

[0345] The terms "non-transitory memory" and “non-transitory storage medium” used herein should be expansively construed to cover any volatile or non-volatile computer memory suitable to the presently disclosed subject matter. The terms shall also be taken to include any medium that is capable of storing or encoding a set of instructions for execution by a processing circuitry and that cause the processing circuitry to perform any one or more of the methodologies of the present disclosure. The terms shall accordingly be taken to include, but not be limited to, a read only memory (“ROM”), random access memory (“RAM”), magnetic disk storage media, optical storage media, flash memory devices, etc.

[0346] It is to be noted that while the present disclosure refers to a controller and / or a processing circuitry being configured to perform various functionalities and / or operations, the functionalities / operations can be performed by the one or more processors of the controller. By way of example, the operations described hereinafter can be performed by a specific processor, or by a combination of processors. The operations described hereinafter can thus be performed by respective processors (or processor combinations), while, optionally, at least some of these operations may be performed by the same processor. The present disclosure should not be limited to be construed as one single processor always performing all the operations.

[0347] It is appreciated that, unless specifically stated otherwise, certain features of the presently disclosed subject matter, which are described in the context of separate embodiments, can also be provided in combination in a single embodiment. Conversely, various features of the presently disclosed subject matter, which are described in the context of a single embodiment, can also be provided separately, or in any suitable sub-combination.

[0348] In embodiments of the presently disclosed subject matter, fewer, more, and / or different stages than those shown in the methods described with reference to the appended drawings may be executed. In embodiments of the presently disclosed subject matter, one or more stages illustrated in the methods described with reference to the appended drawings, may be executed in a different order, and / or one or more groups of stages may be executed simultaneously.

[0349] It will also be understood that the system according to the invention may be, at least partly, implemented on a suitably programmed computer. Likewise, the invention contemplates a computer program being readable by at least one processing circuitry for executing the methods of the invention. The invention further contemplates a non- transitory computer-readable memory tangibly embodying a program of instructions executable by the processing circuitry for executing the methods of the invention.

Claims

CLAIMS1. A device comprising: an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a layer on which at least part of the electro-mechanical device is mounted, and a cover, wherein one or more cavities of the device opened to outer space of the device have a lowest resonance frequency which is equal to or larger than 14KHz.

2. The device of claim 1 , wherein any cavity of the device opened to the outer space of the device, has a lowest resonance frequency which is equal to or higher than 14KHz.

3. The device of claim 1 or of claim 2, wherein the one or more cavities have a lowest resonance frequency which is equal to or larger than a value between 18 KHz and 20KHz.

4. The device of any one of claims 1 to 3, wherein the cover includes a sound- transparent film protecting the electro-mechanical device.

5. The device of any one of claims 1 to 4, wherein: the cover comprises a plurality of side walls, and a portion located above the electro-mechanical device, the one or more cavities include a first cavity located between a first side wall of the plurality of side walls of the cover, and a first side wall of the electro-mechanical device, wherein a transition between: a volume located between the electro-mechanical device and the portion of the cover, and said first cavity, does not include a neck portion.

6. The device of claim 5, wherein the one or more cavities include a second cavity located between: a second side wall of the plurality of side walls of the cover, and a second side wall of the electro-mechanical device, wherein the second cavity has a lowest resonance frequency which is equal to or larger than 14KHz.

7. The device of claim 6, wherein the cover comprises a portion located above the electro-mechanical device, wherein a transition between: the volume located between the electro-mechanical device and the portion, and said second cavity, does not include a neck portion.

8. The device of any one of claims 1 to 7, further comprising a controller located on the layer, electrically connected to the electro-mechanical device, wherein the electro-mechanical device is separated from the controller by a barrier located on the layer.

9. The device of claim 8, wherein (i) or (ii) is met:(i) the barrier corresponds to a material deposited on the layer, separating the electromechanical device from the controller;(ii) the barrier corresponds to an additional wall of the cover, separating the electromechanical device from the controller.

10. The device of any one of claims 1 to 9, further comprising a controller, wherein the electro-mechanical device is located on a first side of the layer, and the controller is located on a second side of the layer, opposite to the first side.

11. The device of claim 10, wherein: the electro-mechanical device comprises a first set of pads or pins, the controller comprises a second set of pads or pins, a position of the first set of pads or pins matches a position of the second set of pads or pins in a plane parallel to the layer.

12. The device of claim 11, wherein the first set of pads or pins is electrically connected to the second set of pads or pins by vias going through the layer.

13. The device of any one of claims 10 to 12, wherein the one or more cavities include a cavity located around the controller.

14. The device of any one of claims 1 to 13, comprising: a plurality of electro-mechanical devices, each of them operative to generate sound waves, each of them comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a plurality of controllers, wherein each given electro-mechanical device of the plurality of electromechanical devices is electrically connected to a given controller of the plurality of controllers, wherein the plurality of electro-mechanical devices is located on a first side of the layer, and the plurality of controllers is located on a second side of the layer, opposite to the first side.

15. The device of claim 14, wherein: each electro-mechanical device of the plurality of electro-mechanical devices comprises a first set of pads or pins, each controller of the plurality of controllers comprises a second set of pads or pins, the position of the first set of pads or pins of said each given electro-mechanical device matches a position of the second set of pads or pins of said given controller, in a plane parallel to the layer.

16. The device of any one of claims 1 to 15, wherein a distance between an upper surface of the electro-mechanical device and the cover is below 1mm.

17. The device of any one of claims 1 to 16, wherein the cover comprises a plurality of side walls, wherein at least one side wall of the plurality of side walls of the coverhas a surface operative to reflect at least part of said sound waves, wherein said surface is tilted with respect to a vertical axis, or with respect to an axis orthogonal to the layer.

18. The device of any one of claims 1 to 17, wherein the cover comprises a plurality of side walls, wherein at least one side wall of the plurality of side walls of the cover has a surface operative to reflect at least part of said sound waves, wherein said surface comprises a plurality of protruding portions, wherein each protruding portion comprises two surfaces operative to reflect at least part of said sound waves towards a different direction.

19. A device comprising: an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a controller electrically connected to the electro-mechanical device, a layer on which the electro-mechanical device and the controller are mounted, a cover comprising a plurality of side walls surrounding the electro-mechanical device and the controller, wherein the electro-mechanical device is separated from the controller by a barrier located on the layer.

20. The device of claim 19, wherein the barrier prevents communication between: a cavity or a volume located between the electro-mechanical device and the cover, and a cavity located between the controller and the cover.

21. The device of claim 19 or of claim 20, wherein the barrier corresponds to a material deposited on the layer, separating the electro-mechanical device from the controller.

22. The device of claim 21, wherein at least one of (i) or (ii) is met:(i) the material comprises an epoxy;(ii) the material comprises glob top.

23. The device of claim 21 or of claim 22, wherein at least one of (iii) or (iv) is met:(iii) the material is further located between an upper surface of the controller and the cover;(iv) the material is further located between a side wall of the controller, and a side wall of the plurality of side walls of the cover.

24. The device of any one of claims 21 to 23, wherein at least part of the material extends from the layer up to a protruding part of the cover configured to cooperate with a sound-transparent film of the cover, protecting the electro-mechanical device.

25. The device of any one of claims 22 to 24, wherein at least part of the material extends from the layer up to the cover, or up to a sound-transparent film of the cover, and protects the electro-mechanical device.

26. The device of claim 19 or of claim 20, wherein the barrier corresponds to an additional wall which is part of the cover, wherein the additional wall separates the electro-mechanical device from the controller.

27. The device of any one of claims 19 to 26, comprising a material located between a side wall of the electro-mechanical device and a side wall of the plurality of side walls of the cover.

28. The device of claim 27, wherein the material prevents air communication between: a cavity or a volume located between the electro-mechanical device and a portion of the cover, and a cavity located between the material and a side wall of the plurality of side walls of the cover.

29. The device of claim 28, wherein: at least part of the material extends from the layer up to a protruding part of the cover configured to cooperate with a sound-transparent film of the cover, protecting the electro-mechanical device, orthe material fills all or a majority of a cavity located between a side wall of the electro-mechanical device, located opposite to a side wall of the electro-mechanical device facing the controller, and a side wall of the cover.

30. The device of any one of claims 19 to 29, comprising a material surrounding four side walls of the electro-mechanical device, wherein the barrier corresponds to part of said material located between the electro-mechanical device and the controller.

31. A device comprising: an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a controller electrically connected to the electro-mechanical device, a layer, and a cover, wherein the electro-mechanical device is located on a first side of the layer, and the controller is located on a second side of the layer, opposite to the first side, wherein the electro-mechanical device is electrically connected to the controller.

32. The device of claim 31, wherein the electro-mechanical device comprises a first set of pads or pins and the controller comprises a second set of pads or pins, wherein a position of the first set of pads or pins matches a position of the second set of pads or pins in a plane parallel to the layer.

33. The device of claim 32, wherein the first set of pads or pins is electrically connected to the second set of pads or pins by vias going through the layer.

34. The device of any one of claims 31 to 33, wherein a transition between: a cavity or a volume located between an upper surface of the electro-mechanical device and the cover, and a cavity located between a side wall of the electro-mechanical device and a side wall of the cover, does not include a neck portion.

35. The device of any one of claims 31 to 34, wherein (i) or (ii) is met:(i) one or more cavities of the device opened to outer space of the device have a lowest resonance frequency which is equal to or larger than 14KHz;.(ii) any cavity of the device opened to the outer space of the device, has a lowest resonance frequency which is equal to or higher than 14KHz.

36. A device comprising: an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a layer on which at least part of the electro-mechanical device is mounted, a cover coupled to the layer, wherein a given cavity is located between an upper surface of the electromechanical device and the cover, wherein (i) or (ii) is met:(i) any cavity of the device opened to this given cavity has a lowest resonance frequency which is equal to or higher than 14KHz;(ii) no cavity of the device is opened to said given cavity.

37. A device comprising: an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a layer on which at least part of the electro-mechanical device is mounted, a cover coupled to the layer, comprising a plurality of side walls, wherein at least one side wall of the plurality of side walls of the cover has a surface operative to reflect at least part of said sound waves, wherein said surface is tilted with respect to a vertical axis, or with respect to an axis orthogonal to the layer.

38. A device comprising: an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a layer on which at least part of the electro-mechanical device is mounted, a cover coupled to the layer, wherein the cover comprises a sound-transparent film protecting the electro-mechanical device, wherein a distance between an upper part of the electro-mechanical device and the sound- transparent film is equal to or smaller than 1mm.

39. A device comprising: an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a layer on which at least part of the electro-mechanical device is mounted, a cover coupled to the layer, comprising a plurality of side walls, wherein at least one side wall of the plurality of side walls of the cover has a surface operative to reflect at least part of said sound waves, wherein said surface comprises a plurality of protruding portions.

40. The device of claim 39, wherein each given protruding portion of the plurality of protruding portions comprises two given surfaces operative to reflect sound waves towards a different direction.

41. The device of claim 40, wherein each given protruding portion of the plurality of protruding portions is associated with a triangular shape in cross-section.

42. A device comprising: an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element,a layer on which at least part of the electro-mechanical device is mounted, a cover coupled to the layer, comprising a plurality of side walls, wherein one or more of the side walls of the cover include one or more elements operative to block relative displacement between the layer and the cover along one or more axes.

43. The device of claim 42, wherein at least one element of the one or more elements is located on a side of the layer.

44. The device of claim 42 or claim 43, wherein at least one element of the one or more elements corresponds to a lip protruding from a side wall of the cover up to a side of the layer.

45. The device of any one of claims 42 to 44, wherein the one or more elements are operative to block a relative translation between the layer and the cover along one or more axes.

46. The device of any one of claims 42 to 45, wherein, for at least one side wall of the plurality of side walls, a maximal distance between the electro-mechanical device and said side wall is equal to, or smaller than 1mm.

47. A device comprising: an electro-mechanical device operative to generate sound waves, comprising an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, a layer on which at least part of the electro-mechanical device is mounted, a cover coupled to the layer, comprising a plurality of side walls, wherein the cover comprises four corners, each corner being located between adjacent side walls of the plurality of side walls of the cover, wherein a given corner of the four corners has a different shape than all other corners of the four corners.

48. The device of claim 47, wherein:the given corner has a rounded shape, which is different from one or more shapes of all other corners of the four corners, or the given corner has a squared shape, which is different from one or more shapes of all other corners of the four corners, or the given corner has a chamfered shape, which is different from one or more shapes of all other corners of the four corners.

49. The device of any one of claims 1 to 48, corresponding to or being part of a digital sound reconstruction speaker.

50. The device of any one of claims 1 to 49, configured to generate ultrasonic waves.

51. A method comprising manufacturing a device, said manufacturing comprising mounting an electro-mechanical device and a controller on at least one layer and fastening a cover to the at least one layer, wherein the electro-mechanical device is operative to generate sound waves and comprises an array of a plurality of actuator elements, each given actuator element of the plurality of actuator elements comprising at least one given electrode and a given moving element, wherein one or more cavities of the device opened to outer space of the device have a lowest resonance frequency which is equal to or larger than 14KHz.

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