Device for recreating a sound reverberation effect and equipped with a MEMS spring

Abstract

MEMS SPRING BASED DEVICE FOR RECREATING A REVERBERATION EFFECT Micro-electromechanical device (100) for distorting an electrical signal to recreate a sound reverberation effect comprising: an input connector (1121) for an incoming electrical signal; an output connector (1122) for an outgoing electrical signal; an input electromechanical transducer (123) coupled to the input connector (1121); an output electromechanical transducer (124) coupled to the output connector (1122); a support structure (121);said device being provided with a MEMS spring (122) having a first end (1222), a second end (1223), the first end and the second end being connected respectively to the input electromechanical transducer (123) by means of an articulation (125) to the output electromechanical transducer (124) by means of another articulation (125), the input electromechanical transducer (123), the output electromechanical transducer (124) and the articulations (125) being partly embedded on the support structure (121), the input electromechanical transducer (123) being configured to set the articulation (125) in motion. Abstract Figure: Figure 1;

Description

Title of the invention: Device for recreating a sound reverberation effect and equipped with a MEMS spring Technical field

[0001] The present invention belongs to the technical field of microelectromechanical systems (MEMS).

[0002] The invention relates more particularly to a miniaturized spring making it possible to recreate the reverberation effect present naturally and in particular in large rooms.

[0003] The invention finds a direct application in the musical field and makes it possible to develop sound effects in an analog and compact manner. State of the art

[0004] The search for sound effects, whether by exploiting the acoustics of particular places or the rendering obtained by the use of certain materials or objects for example, constitutes a subject of constant development.

[0005] Used by both musicians and sound designers, sound effects, whether analog or digital, are constantly being invented in order to explore new fields and contribute to pushing back the boundaries of creativity.

[0006] A well-known effect is that of the reverberation naturally present in concert halls, recording studios, and other performance venues, places in which the walls will reflect the incident acoustic waves with a loss in amplitude which is a function of the type of materials used.

[0007] Thus, reflected acoustic waves will be juxtaposed and arrive with a certain delay at the listeners (or sound capture systems), thus creating an immersive sound experience.

[0008] There are several techniques that allow this reverberation effect to be artificially reproduced.

[0009] First of all, echo chambers were developed at the beginning of the 20th century to reproduce reverberation in small volumes (recording studio, radio studio, etc.).

[0010] Then came spring reverberations which made it possible to reproduce the desired effect. On the other hand, the result obtained was different from that of natural reverberations or echo chambers, making it an effect in its own right with its own sound signature. In addition, and in order to obtain the desired effect, it is necessary for the springs to be long enough to obtain a delay between the different echoes.

[0011] Based on a principle similar to that of springs, plate reverberation was developed in the second half of the 20th century. This time, the sound is transmitted through a metal plate in which complex reflections take place. The sound rendering then comes closer to the acoustics of rooms with significant reverberation.

[0012] On the other hand, the plates used are often heavy and bulky, making them difficult to use.

[0013] Then, with the development of transistors, the devices described above could be replaced by entirely electronic delay lines transmitting the analog signal with a delay of up to several milliseconds.

[0014] Finally, digital reverb effects, which are mainly based on algorithms that recreate sound spaces, are emerging. These effects make it possible to simulate the acoustics of rooms such as concert halls, recording studios, as well as other reverberation effects. In addition, they make it possible to integrate these effects into compact elements, in comparison with the physical examples cited previously.

[0015] The document RAMEREZ, MAM et al. Modeling plate and spring reverberation using a DSP-informed deep neural network, ICASSP 2020-2020 IEEE International Conference on Acoustics, Speech and Signal Processing, pages 241 to 245, describes a method for modeling the reverberation effects obtained in springs and plates. This modeling is based on a neural network to achieve, in particular, deep learning of the nonlinear effects present in spring and plate reverberations. On the other hand, this type of modeling is complex to implement, and the results obtained are an approximation of the physical phenomena present in these reverberation effects.

[0016] The document BIEBAO, S., Numerical simulation of spring reverberation, 16,h International Conference of Digital Audio Effects, September 2013, describes another type of modeling of the reverberation effect in springs and which is based on the calculation of finite differences in the time domain (in English Finite Difference Time Domain, FDTD) to model the vibration of helical springs. Again, it is difficult to model all the physical effects that take place in this type of reverberation effect. These models, although complex, are therefore incomplete and it appears necessary to be particularly vigilant on their numerical stability in order to converge towards solutions.

[0017] The problem arises of developing a device for recreating a reverberation effect, which is compact while guaranteeing a highly faithful rendering of the desired sound effect. Presentation of the invention

[0018] The present invention aims to overcome all or part of the drawbacks presented above, and then proposes a device making it possible to recreate a reverberation effect, said device being equipped with a MEMS spring.

[0019] It is specified here that the term MEMS corresponds to the abbreviation of the English expression Microelectromechanical Systems, which can be translated into French by the expression micro-electromechanical systems. By MEMS springs and cells, and generally speaking, we mean miniaturized components which can in particular be used with electronic circuits or be integrated into microelectronic devices and perform functions equivalent to conventional components.

[0020] According to one embodiment, the present invention relates to a microelectromechanical device for distorting an electrical signal to recreate a sound reverberation effect comprising:

[0021] - an input connector for an incoming electrical signal;

[0022] - an output connector for an outgoing electrical signal;

[0023] - an electromechanical input transducer coupled to the input connector;

[0024] - an electromechanical output transducer coupled to the output connector;

[0025] - a support structure;

[0026] said device being provided with a MEMS spring comprising a first end, a second end, the first end and the second end being respectively connected to the input electromechanical transducer by means of an articulation to the output electromechanical transducer by means of another articulation, the input electromechanical transducer, the output electromechanical transducer and the articulations being partly embedded on the support structure, the input electromechanical transducer being configured to set the articulation in motion.

[0027] By “coupled” is meant here an electrical connection or link which may be direct or indirect (i.e. made through one or more electrical elements or intermediate components).

[0028] Advantageously, the electromechanical input transducer and / or the electromechanical output transducer comprises two blades, in particular coplanar, configured to apply a torsional torque to the joint.

[0029] Advantageously, the blades are piezoelectric elements.

[0030] According to a particular characteristic of the invention, the incoming electrical signal is transmitted on one of the blades of the input electromechanical transducer, while said incoming electrical signal is transmitted in phase opposition on the other blade of said transducer.

[0031] According to another particular characteristic of the invention, the articulation comprises a connecting rod connecting one edge of one blade to another edge of the other blade and an embedding rod connecting the support structure to the connecting rod.

[0032] Advantageously, the MEMS spring is a flat spring, which when said spring is at rest, extends between the first end and the second end in the same plane.

[0033] Another particular characteristic is that the MEMS spring is formed from a succession of MEMS cells, each cell forming one or more undulations, advantageously rectangular or triangular, the succession of cells forming a succession of undulations.

[0034] Advantageously, each MEMS cell is defined by a thickness of between 5 and 20 pm, a band width of between 5 and 100 pm, a half-width of between 100 pm and 2 mm, and an interband spacing of between 5 and 20 pm.

[0035] Advantageously, the MEMS cells have dimensions which are a function of their position along the MEMS spring.

[0036] Advantageously, the device further comprises at least one hermetic housing in which the support structure, the input and output transducers and the MEMS spring are housed, the pressure inside the housing being advantageously between 0.1 Pa and 100 Pa.

[0037] Advantageously, the device further comprises: a printed circuit on which the support structure and an analog processing circuit connected to the output connector are arranged.

[0038] Another object of the invention is a sound production system characterized in that it comprises a micro-electromechanical device for recreating a reverberation effect according to any one of the preceding claims.

[0039] Another object of the invention is a method for manufacturing the microelectromechanical device, comprising the following steps:

[0040] - provide a support, comprising, from its rear face to its front face opposite the rear face: at least a first semiconductor layer and a second semiconductor layer superimposed, and coating the support with a stack comprising a first conductive layer, a layer of piezoelectric material and a second conductive layer,

[0041] - structure the stack and the second semi-conductor layer of the support of so as to produce the input and output transducer in said stack as well as the joints and the MEMS spring in the second semiconductor layer,

[0042] - etch the first semiconductor layer from the rear face of the support so as to release the MEMS spring, joints and input and output transducers. Presentation of the drawings

[0043] The figures are given purely for illustrative purposes for a better understanding of the invention without limiting its scope. The various elements may be represented schematically and are not necessarily on the same scale. Throughout the figures, identical or equivalent elements bear the same numerical reference.

[0044] It is thus illustrated in:

[0045] [Fig-1]: an exploded view of a device for recreating a reverberation effect, according to one embodiment of the invention;

[0046] [Fig.2]: a perspective view of the device for recreating a reverberation effect;

[0047] [Fig.3A]: a top view of a MEMS component of the device recreating a reverberation effect, according to a first embodiment;

[0048] [Fig.3B]: a top view of a MEMS component of the device recreating a reverberation effect, according to a second embodiment;

[0049] [Fig.4]: a top view of a transducer and an articulation of the MEMS component according to the first and second embodiments;

[0050] [Fig.5]: a graph of an electrical signal of an impulse response obtained by means of the device;

[0051] [Fig.6]: three perspective views of a transducer of the device recreating a reverberation effect when the transducer is: in its equilibrium position (A), in an out-of-phase vibration mode (B), in an in-phase vibration mode (C);

[0052] [Fig.7]: an electrical diagram of a differential amplifier assembly for extracting certain components of the signal produced by the device;

[0053] [Fig.8A], [Fig.8B]], [Fig.8C]] and [Fig.8D]]: steps of a manufacturing process of a MEMS component according to the invention;

[0054] [Fig.9A]: a graph of the temporal variations of the frequency content of an electrical signal of an impulse response obtained by means of the device, according to an embodiment of the invention; and

[0055] [Fig.9B]: a graph of the temporal variations of the frequency content of an electrical signal of an impulse response obtained by means of the device, according to another embodiment of the invention. Detailed description of embodiments

[0056] The present invention aims in particular to propose a miniaturized spring reverberation device of the MEMS type.

[0057] [Fig.l] represents an exploded view of a device 100 recreating a reverberation effect, and which comprises a hermetic housing 11 composed of a cover 111, preferably transparent, said cover covering a printed circuit 112, a MEMS component 12.

[0058] The MEMS component 12, which is not shown as a whole in [Fig.l] for the sake of readability, comprises a structure 121, a MEMS spring 122, two transducers 123 and 124, each connected respectively to one end 1222-1223 of the MEMS spring 122 by means of an articulation 125. The MEMS spring 122 is itself composed of a plurality of MEMS cells 1221, one of which is shown with hatching in [Fig.l].

[0059] Advantageously, the MEMS spring 122 is a flat spring.

[0060] In this exemplary embodiment, the transducers 123 and 124 respectively comprise two piezoelectric blades 1231-1232 and 1241-1242. For example, the blades 1231-1232 and 1241-1242 are made of lead zirconate titanoates (PZT).

[0061] The printed circuit 112 comprises in particular an input connector 1121, for transmitting an input signal called a “source” signal to the device 100, an output connector 1122 for transmitting a “reverberated” output signal, this reverberated signal typically being transmitted to an external system such as a sound reproduction or recording system. The “source” signal is an electrical signal, itself resulting from a conversion or transduction of a sound signal to which it is desired to add the reverberation effect.

[0062] In this example, the transducer 123 is configured to convert an input electrical signal into a mechanical vibration that propagates along the MEMS spring 122, and the transducer 124 is used to convert the mechanical vibrations propagating in the MEMS spring 122 into an output electrical signal, the latter signal comprising several components related to the multiple echoes generated within the MEMS spring 122.

[0063] Thus, the transducer 123 is configured to set the joint 125 into rotary motion, preferably in a manner proportional to the input electrical signal.

[0064] The transducers 123 and 124 can be used in differential mode, i.e. with a phase shift of + / - ir between the blades 1231-1232 and 1241-1242, or in common mode, i.e. with a zero phase shift between the blades 1231-1232 and 1241-1242. In the first case, it is possible, for example, to provide an operational amplifier to implement this phase shift.

[0065] The separation of the common and differential modes can be implemented both at the input and at the output of the device 100.

[0066] Finally, the transducers 123 and 124 act as terminating impedances. In order to produce the reverberation effect, i.e. by the presence of echoes in the MEMS spring 122, the mechanical torsional impedances of the transducers 123 and 124 are preferably different from the characteristic mechanical impedance of said spring. To model the dynamic behavior of the device 100, and to dimension the MEMS component 12, an analogy with the termination impedances of a transmission line can be made.

[0067] [Fig. 2] represents a perspective view of the device 100 and when the housing 11 is completely closed. As for [Fig. 1], and for the sake of readability, the MEMS component 12 is not shown as a whole in [Fig. 2],

[0068] In order to limit thermoviscous losses inside the housing 11, said losses dissipating mechanical energy in the MEMS spring 122 when it vibrates, preferably a vacuum between 0.1 Pa and 100 Pa is achieved in the housing 11.

[0069] In other embodiments, the interior volume of the housing is filled with a gas at a given pressure making it possible to minimize thermoviscous losses.

[0070] Thus, and by reducing thermoviscous losses, the quality factor Q, which is defined as being the ratio between the maximum energy contained in a MEMS cell 1221 and the energy which is dissipated by this same cell over an oscillation period, increases. Preferably, and to obtain a number of echoes to generate the desired sound effect, it is preferable that the quality factor Q of a MEMS cell 1221 is greater than 100.

[0071] As previously specified, the MEMS spring 122 is connected, in a fixed manner, at each of its ends 1222-1223 to articulations 125, these articulations being themselves connected in a fixed manner to the transducers 123 and 124. As shown in [Fig.2], the transducers 123 and 124 as well as the articulations 125 are partly embedded on the structure 121 of the MEMS component 12.

[0072] These embeddings are represented by the zones 126 in dotted lines in [Fig.2],

[0073] Thus, these embeddings will constrain the movements of the transducers 123 and 124 as well as the movements of the joints 125 to obtain the desired type of vibrations at the level of the MEMS spring 122. Preferably, the MEMS spring 122 is set in motion by means of the transducer 123 in order to produce torsional movements around its equilibrium position. The blades 1231 and 1232 can be actuated in phase opposition in order to promote this mode of vibration of the MEMS spring 122. In other embodiments, the blades 1231 and 1232 are actuated in phase and by applying the same load to them in order to promote the propagation of a longitudinal and bending mode of vibration within the MEMS spring 122.

[0074] To transmit the input signal to the transducer 123, electrical tracks (not shown here) are present on the printed circuit 112 and connect the connector input 1121 to transducer 123. The same is true for output connector 1122 and transducer 124.

[0075] Finally, in a particular embodiment, the printed circuit 112 has a thickness el 12 of 600 μm, a length L112 of less than 10 mm, a width 1112 of the order of 5 mm, and the cover 111 has a thickness el 11 of at least 1 mm.

[0076] Thus, and due to the materials used and its dimensions, the device 100 is therefore extremely compact and very light, in comparison with existing reverberation systems which typically use springs having a length of several tens of centimeters. The device 100 also has the particularity of requiring only low electrical consumption, in comparison with simulated spring reverberations which require powering a digital signal processor (DSP). Furthermore, the design of the device 100 makes it possible to obtain a high quality factor.

[0077] Advantageously, and thanks to its small dimensions, the device 100 can be directly integrated into sound production systems, such as musical instruments, guitar or bass amplifiers but also acoustic speakers, or as a complementary sound effect in effects pedals.

[0078] [Fig.3A] represents a top view of the MEMS component 12.

[0079] For the sake of readability, the device 100 being a miniaturized device, the MEMS component 12 is not shown as a whole in [Fig.3A]. In addition, the various elements of the MEMS component 12 are deliberately not shown to scale in order to better identify the sizing parameters of the MEMS spring 121.

[0080] Furthermore, the positions of the embeddings of the transducers 123 and 124 as well as the articulations 125 at the level of the zones 126 of the structure 121 are more easily visible in [Fig.3A].

[0081] The joints 125 comprise a connecting rod 125a connecting together a free edge of the blade 1231 with a free edge of the other blade 1232, or a free edge of the blade 1241 with a free edge of the other blade 1242, as well as an embedding rod 125b connecting the support structure 121 to the connecting rod 125a. In the particular embodiment illustrated, the free edge of the blades is a lateral edge.

[0082] However, as a variant, the rods 125a, 125b can be provided respectively on a lower edge of the blade 1231 and on a lower edge of the other blade 1232 or respectively on an upper edge.

[0083] As presented previously, the MEMS spring 121 comprises a number n of MEMS cells 1221, one of which is delimited in [Fig.3A] by dotted lines.

[0084] In one embodiment, the MEMS cell 1221 is formed from one or more rectangular or square shaped corrugations. Each corrugation may be formed as in [Fig.3A], of a succession of first strips which extend in a first direction and connected together two by two by second strips in a second direction orthogonal to the first direction. In this figure, a strip width W p, an interband space it between two first strips and a half-width L p of the first strips are defined. In the example illustrated, the MEMS cell 1221 has a total length L cM which corresponds to two round trips or two successive undulations, as can be seen in [Fig.3A]. In addition, the MEMS cell 1221 is defined by a thickness tm (not shown here).

[0085] The ends 1222 and 1223 of the MEMS spring 121 are characterized respectively by a length Lai and a length Lao.

[0086] Preferably, the MEMS spring 121 is sized such that the echoes are produced with a delay of = 25 ms, as shown in [Fig.5].

[0087] By way of example, and without this presenting a limit to the invention, table 1 below summarizes the dimensions of a MEMS 1222 cell making it possible to obtain a delay of = 25 ms between two echoes.

[0088] [Tableauxl] Parameter Value Thickness of MEMS cell, tm (pm) 5 Interband spacing, it (pm) 5 Band width, Wp (pm) 5 Half width of MEMS cell, Lp (mm) 1000 Length of first end of MEMS spring, Lai (pm) 5 Length of second end of MEMS spring, Lao (pm) 5 Total length of one MEMS cell, Ltot (pm) 45 Number of MEMS cells, n 100 Length of MEMS spring (pm) 4015

[0089] Thus, and for the dimensions given in table 1, the MEMS component 12, which as a reminder is the active part of the device 100 in which the reverberation effect is generated, has a length Li2 which is less than 5 mm, and a width 112 which is less than 3 mm.

[0090] More generally, the interband spacing it is between 5 and 20 pm, the thickness tm is between 5 and 20 pm, the band width Wp is between 5 and 100 pm, the half-width Lp is between 100 pm and 2 mm.

[0091] In other embodiments, the MEMS cell 1221 is formed from a succession of triangular undulations, as shown in [Fig.3B].

[0092] [Fig.4] shows a top view of the transducer 123 and the articulation 125. The following description of [Fig.4] is also valid for the transducer 124. The pentagonal shape of the blades 1231 and 1232 makes it possible to lighten the structure and therefore to increase the resonance frequency of these elements in order to broaden the bandwidth.

[0093] This pentagonal shape is defined by a base width Wa, a top width Wai which is less than the base width Wa, a height La, and a partial height Lab

[0094] These dimensions are optimized in order to obtain a maximum displacement or deformation angle of the end of the blades 1231 and 1232, as shown in [Fig.5] in (B) and (C), while minimizing the surface area of ​​said blades.

[0095] Furthermore, the minimization of the surface area of ​​the blades 1231-1232 and 1241-1242 contributes to the low energy consumption of the device 100.

[0096] The articulation 125, represented by the hatching in [Fig.4], is preferably T-shaped, and is manufactured in the same layer as the blades 1231-1232 and 1241-1242. The articulation is defined by a width Wk of the embedding rod 125b, a length lk of the embedding rod 125b and a length Lk of the connecting rod 125a.

[0097] By way of example, and without this presenting a limit to the invention, table 2 below summarizes the possible dimensions of the transducers 123 and 124 and of the articulation 125.

[0098] [Tables2] Parameter Value Blade base width, Wa (pm) 400 Blade top width, Wai (pm) 200 Blade height, La (pm) 800 Partial blade height, Lai (pm) 400 Width of embedding rod, Wk (pm) 5 Length of embedding rod, lk (pm) 200 Length of connecting rod, Lk (pm) 415

[0099] [Fig.5] represents a graph 300 of an output signal 30 of a response impulse obtained by means of the device 100. In this example, an impulse signal is used to illustrate the reverberation effect generated by the device 100.

[0100] The abscissa axis represents the time scale t, ranging from 0 to 200 ms, and the ordinate axis represents the relative voltage V out of the output signal 30.

[0101] The output signal 30 is composed of a first part 301 which corresponds to the pulse signal transmitted directly through the MEMS spring 122, and a second part 302 in which it is possible to see the multiple echoes which, superimposing themselves, will create the desired reverberation effect.

[0102] In [Fig.5], the first delay d 0 corresponds to the propagation time of the signal through the MEMS spring 122, and the second delay d corresponds to the delay between two successive echoes 3021 and 3022.

[0103] By modifying the parameters listed in Table 1, the properties of the MEMS spring 122 can then be optimized to obtain the desired reverberation effect. Thus, and by way of example, the delay between two successive echoes 3021 and 3022 is directly a function of the number n of MEMS cells 1221: the delay increasing linearly as a function of the number n.

[0104] [Fig.6] shows three perspective views of the transducer 123 when it is in different positions in order to illustrate its principal modes of vibration.

[0105] First, [Fig.6] in (A) represents the transducer 123 in its equilibrium position. In this position, the blades 1231 and 1232 are aligned and do not exhibit any deformations linked to vibrations.

[0106] Then, [Fig.6] in (B) represents the transducer 123, when it vibrates in a so-called “differential” mode, and which corresponds to the propagation in the MEMS spring 122 of a torsion wave. The blades 1231 and 1232 then oscillate in phase opposition around their equilibrium position, seen in (A) and shown diagrammatically by a dotted line representing a z-axis.

[0107] Then, [Fig.6] in (C) represents the transducer 123, when it vibrates in a so-called “common” mode, that is to say a mode where the blades 1231 and 1232 oscillate in phase around their equilibrium position, also shown here by a dotted line representing a z-axis. The same potential difference is also applied to the blades 1231 and 1232. At the MEMS spring 122, this corresponds to the propagation of a combination of a longitudinal and bending wave.

[0108] [Fig.7] represents an electrical diagram 500 of an analog processing assembly 50 comprising differential amplifiers 51 for extracting certain components of the signal produced by the device. This assembly makes it possible to exploit, for example, only the differential vibration mode of the transducer 124, in order to retain only the component of the signal originating from the torsion mode of the MEMS spring 122.

[0109] In the preferred embodiment of the invention, the analog processing assembly 50 comprises two inputs receiving the signals Vlin and V2in coming respectively from the mechanical electrical conversions at the blades 1241 and 1242 of the transducer 124.

[0110] At the output of the analog processing assembly 50, an output signal Vout is obtained, as shown in [Fig.5].

[0111] In addition, the analog processing assembly 50 includes a gain, represented on the electrical diagram 500 by a resistor Rgain and which allows a user to modify the contribution of the torsion and bending modes present in the MEMS spring 122 when it vibrates.

[0112] A particular example of an embodiment of a method for manufacturing a MEMS component 12 as described previously will now be given in connection with FIGS. 8A-8D.

[0113] A possible starting structure is illustrated in [Fig.8A], with a plate (“wafer” according to English terminology) of the BESOI type (for “bonding and etch back silicon-on-insulator”, i.e. silicon on insulator bonded and etched on the rear face), comprising two superimposed semi-conductor layers 202, 204, for example made of silicon, here separated by a typically insulating separation layer and for example of silicon oxide 203.

[0114] The MEMS spring 122 is intended to be formed in an upper semiconductor layer 204, typically the thinnest of the semiconductor layers 202, 204. Similarly, the articulations 125 of the transducers 123 and 124 can be formed in this layer 204, as well as at least part of the anchoring structure 121. It is thus possible to provide for at least partially producing all the mobile elements in the upper layer 204. The lower semiconductor layer 202 can be provided here to form the frame.

[0115] On the thinnest semiconductor layer 204 located on the front face FAV of the plate, a stack comprising: - a first electrode layer 222, for example made of Pt; - a layer 224 of piezoelectric material, for example PZT; then - a second electrode layer 226, for example made of Pt;

[0116] is filed.

[0117] As illustrated in [Fig.8B], this stack is then structured to form the piezoelectric transducers. The piezoelectric transducers are defined by etching. A masking 201A, for example formed from a layer 201 of silicon oxide arranged on the rear face FAR, is provided here and also structured with a view to subsequently carrying out a deep etching step by this rear face FAR.

[0118] As illustrated in [Fig.8C], an etching of the silicon layer 204 so as to define the MEMS spring 122 and the articulations 125 of the transducers 123 and 124 is then carried out.

[0119] Prior to this definition, the transducers are typically protected by a passivation layer 231, for example made of silicon oxide, through which openings are made for electrical contacts 252b, 252a allowing respectively the electrical supply of the upper and lower electrodes of the piezoelectric transducers. A conductive material, for example such as Au, is deposited to form the contacts.

[0120] Then, and as illustrated in [Fig.8D], a deep etching step of the rear face FAR of the plate in order to release the MEMS spring 122 and the deformable structure with the transducers 123 and 124 is then carried out. The lower semiconductor layer 202 is thus etched here.

[0121] [Fig.9A] and [Fig.9B] respectively represent a graph 500a and a graph 500b which illustrate examples of the temporal variations of the frequency contents 50a and 50b of electrical impulse response signals obtained by means of the device according to two distinct embodiments of the invention.

[0122] [Fig.9A] is the spectrogram obtained for a device 100 comprising 200 MEMS cells 1221.

[0123] [Fig.9B] is the spectrogram obtained for a device 100 comprising 100 MEMS cells 1221.

[0124] In Figures 9A and 9B, we can see in particular the dispersive effect along the time axis t, where the propagation time within the device 100 differs as a function of the frequency / .

Claims

Claims

1. A micro-electromechanical device (100) for distorting an electrical signal to recreate a sound reverberation effect comprising: - an input connector (1121) for an incoming electrical signal; - an output connector (1122) for an outgoing electrical signal; - an electromechanical input transducer (123) coupled to the input connector (1121); - an electromechanical output transducer (124) coupled to the output connector (1122); - a support structure (121);- said device being provided with a MEMS spring (122) comprising a first end (1222), a second end (1223), the first end and the second end being connected respectively to the input electromechanical transducer (123) by means of an articulation (125) to the output electromechanical transducer (124) by means of another articulation (125), the input electromechanical transducer (123), the output electromechanical transducer (124) and the articulations (125) being partly embedded on the support structure (121), the input electromechanical transducer (123) being configured to set the articulation (125) in motion.;

2. Device according to claim 1, wherein the input electromechanical transducer (123) and / or the output electromechanical transducer (124) comprises two blades (1231, 1232, 1241, 1242), in particular coplanar, configured to apply a torsional torque to the joint

3. Device according to claim 2, wherein the blades (1231,1232,1241,1242) are piezoelectric elements.

4. Device according to one of claims 2 or 3, in which the incoming electrical signal is transmitted on one of the blades (1231,1232) of the input electromechanical transducer (123), while said incoming electrical signal is transmitted in phase opposition on the other blade (1231,1232) of said transducer.

5. Device according to any one of the preceding claims, in which the articulation (125) comprises a connecting rod (125a) connecting together one edge of one blade (1231,1241) with another edge of the other blade (1232,1242) and an embedding rod (125b) connecting the support structure (121) to the connecting rod (125a).

6. Device according to any one of the preceding claims, in which the MEMS spring (122) is a flat spring, which when said spring is at rest, extends between the first end (1222) and the second end (1223) in the same plane.

7. Device according to any one of the preceding claims, in which the MEMS spring (122) is formed from a succession of MEMS cells (1221), each cell forming one or more undulations, advantageously rectangular or triangular, the succession of cells forming a succession of undulations.

8. Device according to claim 7, wherein each MEMS cell (1221) is defined by a thickness (tm) of between 5 and 20 pm, a bandwidth (Wp) of between 5 and 100 pm, a half-width (Lp) of between 100 pm and 2 mm, and an interband spacing (it) of between 5 and 20 pm.

9. A device according to any one of claims 7 to 8, wherein the MEMS cells (1221) have dimensions which are a function of their position along the MEMS spring (122).

10. Device according to any one of the preceding claims, further comprising at least one hermetic housing (11) in which the support structure (121), the input (123) and output (124) transducers and the MEMS spring (122) are housed, the pressure inside the housing (11) being advantageously between 0.1 Pa and 100 Pa.

11. A device according to any preceding claim, further comprising: a printed circuit (112) on which the support structure (121) and an analog processing circuit (50) connected to the output connector (1122) are arranged.

12. Sound production system characterized in that it comprises a micro-electromechanical device (100) for recreating a reverberation effect according to any one of the preceding claims.

13. A method for manufacturing a device according to one of claims 1 to 11, comprising the following steps: providing a support, comprising, from its rear face (FAR) to its front face (FAV) opposite the rear face: at least a first semiconductor layer (201) and a second semiconductor layer (202) superimposed, and coating the support with a stack comprising a first conductive layer (222), a layer of piezoelectric material (224) and a second conductive layer (226), structuring the stack and the second semiconductor layer (204) of the support so as to produce the input (123) and output (124) transducer in said stack as well as the joints (125) and the MEMS spring (122) in the second semiconductor layer (204), etching the first semiconductor layer (202) from the rear face (FAR) of the support so as to release the ME MS spring (122), the joints (125) and the input (123) and output (124) transducers.

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