Patent Publication Number: US-2017352795-A1

Title: Sensor and/or transducer device and method for operating a sensor and/or transducer device having at least one bending structure, which includes at least one piezoelectric layer

Description:
CROSS REFERENCE 
     The present application claims the benefit under 35 U.S.C. §119 of German Patent Application No. DE 102016210008.4 filed on Jun. 7, 2016, which is expressly incorporated herein by reference in its entirety. 
     FIELD 
     The present invention relates to a sensor and/or transducer device, in particular a microphone. The present invention also relates to a method for operating a sensor and/or transducer device having at least one bending structure, which includes at least one piezoelectric layer. Furthermore, the present invention relates to a method for calibrating a microphone having at least one bending structure, which includes at least one piezoelectric layer. 
     BACKGROUND INFORMATION 
     Sensor and/or transducer devices, which have at least one bending structure, which includes at least one piezoelectric layer, are conventional. The particular bending structure has at least one self-supporting area, which is adjustable, under a compression and/or elongation of the at least one piezoelectric layer, in relation to an anchored area of the bending structure. 
     For example, U.S. Patent Appl. Pub. No. 2014/0339657 A1 describes a piezoelectric microphone which has a plurality of such bending structures. 
     SUMMARY 
     The present invention provides a sensor and/or transducer device, a microphone, a method for operating a sensor and/or transducer device having at least one bending structure, which includes at least one piezoelectric layer, and a method for calibrating a microphone having at least one bending structure, which includes at least one piezoelectric layer. 
     The present invention may provide cost-effective and easily implementable possibilities for at least partially compensating for a deformation, which is triggered by the intrinsic stress gradient in the particular bending structure and is generally undesirable, of the at least one bending structure of the particular sensor and/or transducer device. A gap/air gap, which is typically to be accepted as a result of the deformation caused by the intrinsic stress gradient, and which influences a sensitivity of the particular bending structure (or the sensor and/or transducer device equipped therewith) may therefore easily be reduced in size/closed with the aid of the present invention. The present invention therefore contributes to improving the sensitivity of sensor and transducer devices having at least one bending structure, which includes at least one piezoelectric layer. 
     The intrinsic stress gradient occurring in the bending structure may also be interpreted as a differing mechanical stress (or a differing mechanical tension/a differing intrinsic tension/a differing intrinsic stress) with respect to multiple (piezoelectric and/or non-piezoelectric) layers contacting one another. The intrinsic stress occurring, for example, in the at least one piezoelectric layer of the at least one bending structure of a sensor and/or transducer device may result in particular from the deposition process for producing the at least one piezoelectric layer. Since the consequences of the intrinsic stress are at least reducible with the aid of the present invention, the present invention enables the use of cost-effective and easily/rapidly executable deposition methods for producing the at least one piezoelectric layer (or at least one non-piezoelectric layer), without disadvantages having to be accepted thereafter during operation of the particular sensor and/or transducer device as a result of the intrinsic stress resulting from the deposition method used. The present invention therefore also contributes to reducing the manufacturing costs for sensor and/or transducer devices and improving and/or accelerating a manufacturability of sensor and/or transducer devices. 
     In one advantageous specific embodiment of the sensor and/or transducer device, the bending structure includes, as electrodes, at least one first outer electrode, at least one second outer electrode, and at least one intermediate electrode, which is situated between the at least one first outer electrode and the at least one second outer electrode, and a first piezoelectric layer, which is provided in a first intermediate volume between the at least one first outer electrode and the at least one intermediate electrode, and a second piezoelectric layer, which is provided in a second intermediate volume between the at least one intermediate electrode and the at least one second outer electrode, as the at least one piezoelectric layer. The present invention is therefore also applicable for a layer construction for the at least one bending structure, which is advantageously suitable for detecting an action of a force or a pressure (in particular a soundwave) on the at least one bending structure: In a bending structure having the layer construction described here, in the event of a deformation of the bending structure, a tensile stress occurs in one of the two piezoelectric layers and a compression stress occurs in the other of the two piezoelectric layers. The deformation of the bending structure may therefore be reliably ascertained/demonstrated on the basis of a voltage signal tapped at one of the two piezoelectric layers. 
     For example, the bending structure may include, as electrodes, only the first outer electrode, the second outer electrode, and the intermediate electrode situated between the first outer electrode and the second outer electrode, the electronic unit being able to be designed to output at least one electric output signal with respect to a sensing voltage applied between the first outer electrode and the intermediate electrode and to apply the predefined or established actuator voltage between the intermediate electrode and the second outer electrode. This specific embodiment of the sensor and/or transducer device therefore requires (despite the advantageous compensation ability of the deformation triggered by the particular intrinsic stress gradient in the bending structure) only three electrodes per bending structure. In one alternative specific embodiment, at least two of the electrodes may also be used both for balancing the sensing voltage applied between them and for applying the particular actuator voltage between them at the same time. In this case, the particular actuator voltage (as a DC voltage signal) may be filtered out of the sensing voltage (as an AC voltage signal) with the aid of a cost-effective filter (for example, a low-pass filter). 
     In another advantageous specific embodiment of the sensor and/or transducer device, the bending structure includes a first sensing electrode and a first actuator electrode as the at least one first outer electrode, a second sensing electrode and a second actuator electrode as the at least one second outer electrode, and a third sensing electrode, which is located between the first sensing electrode and the second sensing electrode, and a third actuator electrode, which is located between the first actuator electrode and the second actuator electrode, as the at least one intermediate electrode. In this case, the electronic unit is preferably designed to output at least one electrical output signal with respect to at least one sensing voltage applied between two of the sensing electrodes at a time and to apply the at least one predefined or established actuator voltage between two of the actuator electrodes at a time. Sensing and actuation may therefore be clearly separated. 
     In one advantageous refinement, the sensor and/or transducer device has at least two bending structures, which each include the at least one piezoelectric layer, and the electronic unit is designed to apply different predefined or established actuator voltages between the electrodes of the various bending structures. With the aid of the present invention, it is therefore also possible to react to the fact that the occurring intrinsic stress gradient may vary (randomly) between the various bending structures. Nonetheless, it may be ensured with the aid of the present invention that each of the at least two bending structures has a form optimized for operation/sensitivity of the sensor and/or transducer device. 
     The above-described advantages are also ensured in a microphone having such a sensor and/or transducer device. 
     In one advantageous specific embodiment of the microphone, the electronic unit is additionally designed to establish a minimum limiting value of a frequency range of sound waves which may be amplified with the aid of the microphone, by applying the at least one predefined or established actuator voltage between two of the electrodes at a time of the bending structure with the aid of the electronic unit in such a way that the deformation of the bending structure triggered by the intrinsic stress gradient is at least partially compensated for or increased. As explained in greater detail hereafter, the minimum limiting value of the frequency range of sound waves which may be amplified may be adapted in particular to surroundings conditions. 
     Carrying out the corresponding method for operating a sensor and/or transducer device having at least one bending structure, which includes at least one piezoelectric layer, also causes the above-described advantages. It is to be noted that the method is refinable according to the above-described specific embodiments of the sensor and/or transducer device. 
     Furthermore, carrying out the corresponding method for calibrating a microphone having at least one bending structure, which includes at least one piezoelectric layer, also yields the above-mentioned advantages. The method for calibrating a microphone having at least one bending structure, which includes at least one piezoelectric layer, is accordingly also refinable according to the above-described specific embodiments of the sensor and/or transducer device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the present invention are explained below on the basis of the figures. 
         FIGS. 1 a  through 1 d    show schematic views and a circuit of a first specific embodiment of the sensor and/or transducer device. 
         FIGS. 2 a  and 2 b    show schematic views of a second specific embodiment of the sensor and/or transducer device. 
         FIG. 3  shows a flow chart to explain a method for operating a sensor and/or transducer device having at least one bending structure, which includes at least one piezoelectric layer. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
       FIGS. 1 a  through 1 d    show schematic views and a circuit of a first specific embodiment of the sensor and/or transducer device. 
     The sensor and/or transducer device which is schematically shown with the aid of  FIGS. 1 a  through 1 d    may also be referred to as a sound sensor device and/or sound transducer device. The sensor and/or transducer device is designed as a microphone, for example. However, it is to be noted that the implementability of the sensor and/or transducer device described hereafter is not limited to microphones. For example, the sensor and/or transducer device may also be used for a variety of inertial sensor devices. 
     The sensor and/or transducer device of  FIGS. 1 a  through 1 d    has a (single) bending structure  10 . Alternatively, however, the sensor and/or transducer device may also have multiple bending structures  10 , in particular a plurality of bending structures  10 , each having the corresponding features. Bending structure  10  includes at least one piezoelectric layer  12  and  14 , single piezoelectric layer or each of piezoelectric layers  12  and  14  each at least partially filling up an intermediate volume between at least two electrodes  16  through  20  of bending structure  10 . Bending structure  10  may be designed, for example, as a diaphragm, in particular as a diaphragm equipped with slots and/or holes. Bending structure  10  may also be understood as a bending bar structure, for example, a bar-shaped and/or web-shaped bending bar structure. It is to be noted that bending structure  10  may also have a variety of other forms. 
     In the specific embodiment of  FIGS. 1 a    through  1   d,  bending structure  10  has, as electrodes  16  through  20 , a first outer electrode  16 , a second outer electrode  18 , and an intermediate electrode  20 , which is situated/located between first outer electrode  16  and second outer electrode  18 . A first intermediate volume between first outer electrode  16  and intermediate electrode  20  is at least partially (in particular completely) filled using a first piezoelectric layer  12 . Accordingly, a second intermediate volume between intermediate electrode  20  and second outer electrode  18  is at least partially (in particular completely) filled using a second piezoelectric layer  14 . By way of example, first piezoelectric layer  12  is deposited directly on first outer electrode  16  and intermediate electrode  20  is formed directly on a surface of first piezoelectric layer  12  directed away from first outer electrode  16 , while second piezoelectric layer  14  is deposited directly on intermediate electrode  20  and second outer electrode  18  is formed directly on a surface of second piezoelectric layer  14  directed away from intermediate electrode  20 . However, it is to be noted that an implementability of bending structure  10  is not limited to the layer construction shown in  FIGS. 1 a    through  1   c.  For example, in addition to first piezoelectric layer  12  and/or second piezoelectric layer  14 , at least one further intermediate layer may also be located between first outer electrode  16  and intermediate electrode  20  and/or intermediate electrode  20  and second outer electrode  18 . 
     Electrodes  16  through  20  may (perpendicularly in relation to a direction from first outer electrode  16  to second outer electrode  18 ) have an extension a, which is significantly less than an extension A of the at least one piezoelectric layer  12  and  14  (perpendicularly in relation to a direction from first outer electrode  16  to second outer electrode  18 ). For example, an extension a of electrodes  16  through  20  is approximately one-third of extension A of piezoelectric layers  12  and  14 . Notwithstanding the depiction in  FIGS. 1 a    through  1   c,  electrodes  16  through  20  may also have different extensions a and/or piezoelectric layers  12  and  14  may have extensions A which differ from one another. 
     Instead of the design of bending structure  10  having two piezoelectric layers  12  and  14 , as shown in  FIGS. 1 a    through  1   c,  however, instead of one of piezoelectric layers  12  and  14 , a non-piezoelectric layer may be situated. One of outer electrodes  16  or  18  may optionally be saved in this case. 
     Bending structure  10  has at least one self-supporting area  10   a/ at least one self-supporting end, which is adjustable under a compression and/or elongation of the at least one piezoelectric layer  12  and  14  in relation to an anchored area  10   b/ anchored end of bending structure  10 . Bending structure  10  is therefore deformable with the aid of a force exerted thereon and/or a pressure exerted thereon, the at least one piezoelectric layer  12  and  14  being compressed and/or elongated. Since a variety of options are possible for fixing anchored area  10   b/ anchored end, this will not be discussed in greater detail here. 
     Before a release of the at least one self-supporting area  10   a/ self-supporting end of bending structure  10  (in general by removing a sacrificial layer material), bending structure  10  is provided in an initial position, which is shown with the aid of lines  22  in  FIG. 1   a.  During a formation of bending structure  10  using at least one deposition method (for example, for depositing the at least one piezoelectric layer  12  and  14 ), however, an intrinsic stress gradient is frequently formed, which, after the release of the at least one self-supporting area  10   a/ self-supporting end of bending structure  10 , results in a deformation of bending structure  10  out of the initial position. The deformation of bending structure  10  triggered by the intrinsic stress gradient in bending structure  10  results in the example of  FIG. 1 a    in an opening/an enlargement of a gap/air gap  24  between self-supporting area  10   a  of bending structure  10 , which is directed away from anchored area  10   b,  and a structure  26  adjacent thereto. (Adjacent structure  26  may be formed, for example, from the material of the at least one piezoelectric layer  12  and  14 .) Gap  24  may be in particular in an order of magnitude of several tens of micrometers (10 μm). A gap size of gap  24  may also vary significantly as a result of scattering. 
     The deformation of bending structure  10  triggered by the intrinsic stress gradient (in bending structure  10 ) may typically impair a sensitivity of the sensor and/or transducer device. In a sensor and/or transducer device used as a microphone, gap  24  frequently causes a variable “leak resistance,” which makes it impossible to amplify low sound frequencies. 
     However, the sensor and/or transducer device has a (schematically shown) electronic unit  28 , which is designed to apply at least one actuator voltage Ua between two of electrodes  16  through  20  at a time of bending structure  10  in such a way that the deformation of bending structure  10  triggered by the intrinsic stress gradient may be at least partially compensated for (see  FIG. 1 b   ). Gap  24  shown in  FIG. 1 a    may therefore be reduced in size/closed with the aid of electronic unit  28 . 
     Typical effects of intermediate gap  24  on a sensitivity of bending structure  10 /the sensor and/or transducer device equipped therewith therefore no longer have to be accepted due to the equipping of the sensor and/or transducer device with electronic unit  28 . Equipping the sensor and/or transducer device with advantageously designed electronic unit  28  therefore contributes to improving the sensitivity of bending structure  10 /the sensor and/or transducer device equipped therewith. 
       FIG. 1 b    shows a form of bending structure  10  in which no sound wave is incident on a receiving surface  30  of bending structure  10 . The deformation of bending structure  10  which may be caused by the intrinsic stress gradient is shown in  FIG. 1 b    with the aid of lines  32 . The at least one actuator voltage Ua, which is applied with the aid of electronic unit  28  between electrodes  16  through  20 , causes “bending back” of bending structure  10  in this situation, in adaptation to its initial position (before the release of the at least one self-supporting area  10   a/ self-supporting end). Voltage Ua may be overlaid on the sensing voltage as a DC voltage, as shown in  FIG. 1 d    as an electronic circuit.  FIG. 1 c    shows a configuration of circuit  28  alternative thereto, in which the actuator voltage does not act on the same electrode pair as the sensing, which enables a simplified electronic circuit. 
     The at least one actuator voltage Ua may be at least one (permanently) predefined actuator voltage Ua or at least one (newly) established actuator voltage Ua. For example, the at least one (permanently) predefined actuator voltage Ua may be stored unerasably on a (nonerasable) memory  28   a.  During a startup of the sensor and/or transducer device, memory  28   a  may be read out automatically and the at least one actuator voltage Ua may subsequently be applied accordingly. Alternatively, the sensor and/or transducer device may also be designed to (regularly) carry out a self-calibration to predetermine/newly predetermine the at least one actuator voltage Ua and possibly to buffer the at least one actuator voltage Ua subsequently on (erasable) memory  28   a.  Advantageous possibilities for establishing/reestablishing the at least one actuator voltage Ua are also described hereafter. The present invention therefore provides extremely sensitive sensor and/or transducer devices. 
     It is also to be noted that to manufacture the sensor and/or transducer device described here, only comparatively few requirements are to be maintained by the at least one deposition method carried out to form bending structure  10 . Since the intrinsic stress gradient which results in bending structure  10  during the particular deposition method which is carried out, or the effects thereof on bending structure  10 , may be easily compensated for, a variety of deposition methods which may be carried out simply and rapidly may be used (in particular to manufacture the at least one piezoelectric layer  12  and  14 ). In addition, it is not necessary to form at least one stabilizing intermediate layer on bending structure  10 , to counteract an intrinsic stress gradient occurring in the at least one piezoelectric layer  12  and  14 . This reduces the manufacturing costs of bending structure  10 , or the sensor and/or transducer device equipped therewith. 
       FIG. 1 c    shows bending structure  10  during an incidence of a soundwave  34  on receiving surface  30 . As is apparent, soundwave  34  causes a significant deformation of bending structure  10 , which results, for example, in a compression stress  36  in first piezoelectric layer  12  and a tensile stress  38  in second piezoelectric layer  14 . The deformation of bending structure  10  triggered by sound signal  34  may therefore be ascertained/demonstrated with the aid of at least one sensing voltage Us tapped between two of electrodes  16  through  20 . Electronic unit  28  may therefore output a corresponding electrical output signal  40  with respect to the at least one sensing voltage Us, or with respect to soundwave  34 . It is to be noted that the compensation of the intrinsic stress gradient caused by the at least one applied actuator voltage Ua does not impair or hardly impairs a reaction of bending structure  10  to the incidence of soundwave  34  on receiving surface  30 . 
     As is apparent in  FIG. 1   c,  sound signal  34  causes significant compressions/elongations of the at least one piezoelectric layer  12  and  14 , in particular close to the at least one anchored area  10   b/ anchored end of bending structure  10 . Electrodes  16  through  20  are therefore preferably located near to or directly on anchored area  10   b/ anchored end of bending structure  10 . 
     Electronic unit  28  may also be designed in particular to establish a minimum limiting value of a frequency range of soundwave  34  which may be amplified (with the aid of the sensor and/or transducer device designed as a microphone), in that the at least one predefined or established actuator voltage Ua may be applied/is applied between two of electrodes  16  through  20  of bending structure  10  at a time with the aid of electronic unit  28 , in such a way that the deformation of bending structure  10  triggered by the intrinsic stress gradient is at least partially compensated for or increased. 
       FIG. 1 d    shows an example of a possible circuit of electronic unit  28 , in which actuator voltage Ua and sensing voltage Us are measured at the same electrode pair (see  FIG. 1 b   ). A voltage source (Vctrl in  FIG. 1 d   ) generates a DC voltage, which is applied via a high resistance to the sensing or actuator electrodes/actuation electrodes. The low-pass filter thus formed from R and the capacitance of the sensor/actuator Cs has a preferably low limiting frequency (&lt;50 Hz), which is advantageously less than the lowest sensing frequency of the microphone/sensor. The output signal is separated by a capacitor C from actuator DC voltage component Ua at the electrodes and output  40  via an amplifier  42  having a low output impedance. 
     In the specific embodiment of  FIG. 1   c,  electronic unit  28  is designed to apply predefined or established actuator voltage Ua between intermediate electrode  20  and second outer electrode  18  and to output the at least one electrical output signal  40  with respect to sensing voltage Us applied between first outer electrode  16  and intermediate electrode  20 . Electronic unit  28  may also be designed to apply predefined or established actuator voltage Ua between first outer electrode  16  and intermediate electrode  20  and to output the at least one electrical output signal with respect to sensing voltage Us applied between intermediate electrode  20  and second outer electrode  18 . 
     In another alternative specific embodiment, electronic unit  28  may also be designed to use at least two of electrodes  16  through  20  both for applying the at least one predefined or established actuator voltage Ua and for simultaneously tapping the at least one sensing voltage Us. If desired, in this case a filter may be used for filtering out the at least one actuator voltage Ua (as a DC voltage signal) from the at least one sensing voltage Us (as an AC voltage signal). 
       FIGS. 2 a  and 2 b    show schematic views of a second specific embodiment of the sensor and/or transducer device. 
     The sensor and/or transducer device which is schematically shown in  FIGS. 2 a  and 2 b    has, as a supplement to the above-described specific embodiment, in addition to electrodes  16  through  20  (already described above) used as sensing electrodes  16  through  20 , also a first actuator electrode  50 , a second actuator electrode  52 , and a third actuator electrode  54 . First actuator electrode  50  is located together with first sensing electrode/first outer electrode  16  on a side/surface of first piezoelectric layer  12  directed away from second piezoelectric layer  14 . Second actuator electrode  52  is situated together with second outer electrode/second sensing electrode  18  on a side/surface of second piezoelectric layer  14  directed away from first piezoelectric layer  12 . Third actuator electrode  54  is located together with intermediate electrode/third sensing electrode  20  between piezoelectric layers  12  and  14 . 
     As is apparent on the basis of a comparison of  FIGS. 2 a  and 2 b   , electronic unit  28  is designed to apply the at least one predefined or established actuator voltage Ua between two of actuator electrodes  50  through  54 . In addition, the at least one sensing voltage Us may be tapped at at least two of sensing electrodes  16  through  20 , or the at least one electrical output signal  40  may be output with respect to the at least one sensing voltage Us applied between two of sensing electrode  16  through  20 . Reference is made to the above-described specific embodiment with respect to further properties of the sensor and/or transducer device schematically shown in  FIGS. 2 a  and 2 b   . 
     It is to be noted that the specific embodiment of  FIGS. 2 a  and 2 b    achieves a complete separation between sensing and actuation by adding electrodes  50  through  54 , without this significantly increasing the manufacturing costs or an installation space requirement/an extension of bending structure  10 . In particular, the manufacture of actuator electrodes  50  through  54  in addition to sensing electrodes  16  through  20  does not require any additional fabrication steps or any space usable in another way. 
     In general, an extension al of sensing electrodes  16  through  20  (perpendicular in relation to the direction from first outer electrode  16  to second outer electrode  18 ) is approximately one-third of extension A of piezoelectric layers  12  and  14  (perpendicular in relation to the direction from first outer electrode  16  to second outer electrode  18 ). Therefore, actuator electrodes  50  through  54  may be formed having a comparatively large extension a 2  (perpendicular in relation to the direction from first outer electrode  16  to second outer electrode  18 ). Actuator electrodes  50  through  54  may be formed, for example, (almost) twice as large as sensing electrodes  16  through  20 . Therefore, on the other hand, the deformation of bending structure  10  resulting from the intrinsic stress gradient may already be counteracted with the aid of at least one comparatively low actuator voltage Ua. 
     In another specific embodiment, the above-described techniques may also be combined with one another. An additional DC voltage signal may be applied to sensing electrodes  16  through  20 , which are preferably located close to or directly on anchored area  10   b,  so that sensing electrodes  16  through  20  are also used for counteracting the intrinsic stress gradient. This combination has the additional advantage of further smoothing of bending structure  10 . In addition, at least one additional sensing voltage may also be tapped at actuator electrodes  50  through  54 . 
     The above-described specific embodiments may have, as a refinement, instead of single bending structure  10 , at least two, in particular multiple bending structures  10 , which in particular each include the at least one piezoelectric layer  12  and  14 . In this case, electronic unit  28  is preferably designed to apply different predefined or established actuator voltages Ua between electrodes  16  through  20  and  50  through  54  of various bending structures  10 . 
     As an additional refinement, each of the above-described sensor and/or transducer devices may also be designed for self-optimization, in that they measure their sound amplification during the operation and set it to an optimized value by adjusting the at least one bending structure  10 . This also contributes to improving their functionality and to increasing their sensitivity. 
       FIG. 3  shows a flow chart to explain a method for operating a sensor and/or transducer device having at least one bending structure, which includes at least one piezoelectric layer. 
     The method has at least one method step S 1 , in which a deformation of the bending structure triggered by an intrinsic stress gradient in the bending structure, by which at least one self-supporting area of the bending structure is adjusted in relation to an anchored area of the bending structure under a compression and/or elongation of the at least one piezoelectric layer, is at least partially compensated for. This is carried out by applying at least one predefined or established actuator voltage between two of the electrodes of the bending structure at a time, whose intermediate volume is at least partially filled using the at least one piezoelectric layer. At least two bending structures may possibly also be “bent” into a more optimized form in method step S 1 . For this purpose, different predefined or established actuator voltages may be applied between the electrodes of various bending structures. 
     Method step S 1  may be carried out in particular to calibrate a sensor and/or transducer device which is designed as a microphone, having the at least one bending structure, which includes the at least one piezoelectric layer. A minimum limiting value of a frequency range which may be amplified (with the aid of the microphone/the particular bending structure) of sound waves is set, by applying the at least one predefined or established actuator voltage between two of the electrodes of the bending structure at a time (whose intermediate volume is at least partially filled using the at least one piezoelectric layer) to at least partially compensate for or increase the deformation of the bending structure triggered by the intrinsic stress gradient in the bending structure (due to which the at least one self-supporting area is adjusted in relation to the anchored area of the bending structure under a compression and/or elongation of the at least one piezoelectric layer). 
     Method step S 1  may be carried out after a fabrication of the sensor and/or transducer device. Alternatively, at least method step S 1  may also be regularly repeated to calibrate the sensor and/or transducer device. This makes it possible to reestablish the at least one actuator voltage based on calibration measurements or on surroundings conditions. 
     For example, windy surroundings may make amplification of certain low frequency sound signals impossible, since this would overload the amplifier. Under these conditions, it is advantageous if the minimum frequency limiting value is automatically increased in such a way that wind noises are already mechanically filtered out on the sensor side. In calm surroundings, the minimum limiting value may be established at the lowest possible value, in contrast, which significantly improves a signal quality. Method step S 1  is therefore preferably carried out in such a way that in calm surroundings, a first minimum limiting value of the frequency range of sound waves which may be amplified is set with the aid of at least one predefined or established first actuator voltage, and in windy surroundings, a second limiting value, which is greater compared to the first minimum limiting value, of the frequency range of sound waves which may be amplified is set with the aid of at least one predefined or established second actuator voltage. 
     In one refinement, prior to method step S 1 , an optional method step S 2  may also be carried out to establish the at least one actuator voltage. For example, at least one initial value for at least one lower limiting value of sound waves which may be amplified with the aid of the at least one bending structure may be measured, and subsequently the at least one actuator voltage may be established in consideration of the at least one measured initial value. Alternatively, other methods may also be applied for directly demonstrating the deformation of the at least one bending structure existing due to the at least one intrinsic stress gradient, in order to establish the at least one actuator voltage. For example, the deformation of the at least one bending structure may be measured with the aid of optical methods (in particular interferometry, for example). In all exemplary embodiments of method step S 2  described here, the at least one actuator voltage may be established in consideration of the particular obtained information in such a way that the intrinsic stress gradient in the bending structure (and/or its consequences) is at least partially compensated for. 
     The at least one actuator voltage established in method step S 2  may be stored on a nonerasable memory. If method step S 2  is repeated multiple times for a self-calibration during operation of the sensor and/or transducer device, the at least one actuator voltage established in method step S 2  may also be stored on a nonerasable memory. During a startup of the sensor and/or transducer device, the memory may be read out automatically and the at least one actuator voltage may subsequently be applied accordingly.