Abstract:
An interface for expanding a signal starting from a first sensing signal and a second sensing signal, wherein a receiving intensity measuring element generates an intensity signal; and a selector is controlled to select each time the first sensing signal, the second sensing signal, or a combined signal deriving from a weighted combination of these signals. The selector uses a plurality of thresholds variable as a function of the intensity signal.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to an interface for expanding the dynamic interval of an input signal, in particular of an audio signal of an acoustic transducer having two detection structures, and to the related method. 
         [0003]    2. Description of the Related Art 
         [0004]    Acoustic transducers are known, for example MEMS (MicroElectroMechanical System) microphones, comprising a micromechanical sensitive structure, configured to transduce acoustic pressure waves into an electrical quantity (for example, a capacitive variation), and a reading electronics, configured to execute appropriate processing operations (including amplification and filtering) of the electrical quantity for supplying an electrical output signal, whether analog (for example, a voltage) or digital (for example, a PDM—Pulse Density Modulation—signal). 
         [0005]    The electrical signal, possibly processed further by an electronic interface, is then made available for an external electronic system, for example a controller of an electronic apparatus incorporating the acoustic transducer. 
         [0006]    The micromechanical sensitive structure in general comprises a mobile electrode, implemented as a diaphragm or membrane, facing a fixed electrode to form the plates of a variable capacitance sensing capacitor. The mobile electrode is generally anchored, through a perimetral portion, to a substrate, while a central portion thereof is free to move or bend in response to the pressure exerted by incident acoustic pressure waves and thus to modify the capacitance of the sensing capacitor. This capacitance variation affects the electrical signal generated by the sensitive structure (typically the voltage across the capacitor). 
         [0007]    In general, the electrical performance of the acoustic transducer, and in particular its sensitivity, depends upon the mechanical characteristics of the sensitive detection structure, and moreover upon the configuration of the associated, front and rear, acoustic chambers, i.e., the chambers facing a respective, front or rear, face of the diaphragm and traversed in use by the pressure waves incident on the diaphragm and departing therefrom. These different characteristics are thus exploited in order to obtain a wide dynamic interval. 
         [0008]    In fact, in numerous applications it is important to detect acoustic pressure waves with a wide dynamic interval, i.e., signals having a low SPL (Sound Pressure Level), a high sensitivity, and a high SNR (Signal-to-Noise Ratio) and signals having a high SPL, a lower sensitivity, and a reduced SNR. 
         [0009]    Consequently, in the detection of acoustic pressure waves, it is important to reach an optimal compromise between wide dynamic interval, high sensitivity, and high signal-to-noise ratio. 
         [0010]    U.S. Pat. No. 6,271,780 describes a solution for increasing the dynamic interval in an acoustic system, comprising an ADC (analog-to-digital converter), configured to receive an analog sensing signal from an acoustic transducer. This solution envisages subjecting the analog input signal, in parallel, to two signal processing paths, having a first, analog, portion and a second, digital, portion, and each having a respective amplification and gain factor for adapting to signals with low and high sound pressure level, respectively. The two digital signals at the output of the two processing paths are combined for supplying a resulting output signal. Prior to combination, the two signals have be subjected to an equalization, to take into account differences of gain, offset, and phase generated by the previous operations of processing of the signal, in part of an analog type, and thus prevent any distortion of the resulting output signal. 
         [0011]    The above solution is not free from problems, linked principally to the complexity of the processing chain, to a non-negligible sensitivity to noise and oscillations of the input signal, to a low configurability, and to a non-optimal signal-to-noise ratio. 
         [0012]    Another solution is described in US Patent Publication Number 2014/0133677 in the name of the present applicant. 
         [0013]    In general, the present disclosure is directed to an improvement over the known solutions in order to extend the dynamic interval in the detection of signals, such as acoustic pressure waves, at the same time reducing the onset of artefacts during switching between channels. 
       BRIEF SUMMARY 
       [0014]    Embodiments of the present disclosure are directed to a device that includes an electronic interface configured to expand a signal from a first sensing and a second sensing signal to detect a physical quantity, the signal having a first and a second dynamic interval. The electronic interface includes a first input configured to receive the first sensing signal, a second input configured to receive the second sensing signal, an output configured to supply an expanded dynamic output signal, an intensity measuring element coupled to an input between the first and second inputs and configured to generate an intensity signal, and a recombining engine that includes a reconstructed signal generator configured to receive a first level adapted signal and a second level adapted signal, correlated to the first sensing signal and to the second sensing signal, respectively, and to supply a reconstructed signal selectively correlated to the first level adapted signal, the second level adapted signal, or a combined signal derived from a weighted combination of the first and second level adapted signals, the reconstructed signal generator being configured so that the reconstructed signal switches between the first level adapted signal, the second level adapted signal, and the combined signal using a plurality of thresholds variable as a function of the intensity signal. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0015]    For a better understanding of the present disclosure, preferred embodiments thereof are now described, purely by way of non-limiting example and with reference to the attached drawings, wherein: 
           [0016]      FIG. 1  is a block diagram of an embodiment of the present electronic interface, coupled to an acoustic transducer; 
           [0017]      FIG. 2  shows a graph regarding acoustic quantities associated to the interface represented in  FIG. 1 ; 
           [0018]      FIG. 3  is a graph representing conceptually the generation of the output signal of the interface of  FIG. 1 ; 
           [0019]      FIG. 4  is a block diagram of a different embodiment of the present electronic interface; 
           [0020]      FIGS. 5-8  are flowcharts regarding operations carried out by the present electronic interface; 
           [0021]      FIG. 9  shows a variant of a block of  FIG. 1 ; and 
           [0022]      FIG. 10  is a variant of the graph if  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0023]      FIG. 1  shows a block diagram of an interface  1 , here connected to the output of an acoustic transducer, designated by  2 . 
         [0024]    The interface  1  may be obtained via a hardware circuit of an analog and/or digital type or be implemented by a computer programmed with software or firmware; in the example described hereinafter, it is provided by a software-programmed computer, without, however, the following description implying any loss of generality. 
         [0025]    Consequently, even though the following description uses the term “signal”, this term also covers the digital implementation and in particular refers each time to the processed digital sample or to the sequence of processed digital samples. 
         [0026]    The acoustic transducer  2 , for example a MEMS microphone, illustrated schematically herein, comprises two distinct sensitive structures  2   a  and  2   b.  For instance, the sensitive structures  2   a  and  2   b  are micromechanical structures provided in distinct dice of semiconductor material or in distinct portions of a same die of semiconductor material, as distinct membranes or diaphragms. Alternatively, the two sensitive structures  2   a  and  2   b  may be formed by a same diaphragm having distinct areas of sensitivity, as described, for example, in WO2012093598. 
         [0027]    The sensitive structures  2   a,    2   b  are represented schematically in  FIG. 1  a respective capacitor having a variable capacitance as a function of the incident acoustic pressure waves, and have different mechanical characteristics, for example as to different stiffness to deformations (and thus different sensitivity), which determine different electrical characteristics in the detection of the acoustic pressure waves. 
         [0028]    The acoustic transducer  2  further comprises an ASIC  3 , having a first processing element  3   a,  coupled to the first sensitive structure  2   a,  and supplying at a first output a first sensing signal S_in 1  as a function of the electrical signals transduced by the first sensitive structure  2   a;  and a second processing element  3   b,  coupled to the second sensitive structure  2   b,  and supplying on a second output a second sensing signal S_in 2 , as a function of the electrical signals transduced by the second sensitive structure  2   b.  The sensing signals S_in 1  and S_in 2  are typically digital signals, but may also be analog signals. Thus, according to the type of sensing signal S_in 1 , S_in 2 , the processing elements  3   a,    3   b  execute sampling, preamplification and/or filtering operations, in a per se known manner. 
         [0029]    In particular, the first sensitive structure  2   a  may be more flexible and thus able to detect lower acoustic signals, having a first maximum sound pressure level, for example an AOP (Acoustic Overload Point) equal to 120 dBSPL, whereas the second sensitive structure  2   b  may be more rigid, and thus able to detect higher acoustic signals, having a second maximum sound pressure level, higher than the first maximum level, for example an AOP equal to 140 dBSPL. 
         [0030]    Furthermore, the two sensitive structures  2   a,    2   b  may have a same dynamic noise range DNR. 
         [0031]      FIG. 2  shows, for example, the dynamic intervals of the sensing signals S_in 1  and S_in 2  of an acoustic transducer  2  having the maximum sound pressure levels referred to above (different saturation values) and a same dynamic noise range DNR of 89 dB. 
         [0032]    For a same signal (i.e., in the presence of a same SPL value) the first channel  3   a  thus generates an electrical signal having a higher value than the second channel  3   b,  as may be noted immediately in the case of a sound pressure level of 94 dBSPL (S_in 1 =−26 dBFs and S_in 2 =−46 dBFs). 
         [0033]    Consequently, as explained hereinafter, the interface carries out a level adaptation. For instance, in the embodiment represented in  FIG. 1 , the first sensing signal S_in 1  is reduced by a value equal to the level difference at the value of sound pressure level of 94 dBSPL, thus generating a first level adapted signal S_in 1   d.  Alternatively (as illustrated in  FIG. 4 ), it is possible to increase the second sensing signal S_in 2  by the same difference, thus generating a second level adapted signal S_in 2   d.    
         [0034]    As described in detail hereinafter, the electronic interface  1  carries out a combination of the first and second sensing signals S_in 1 , S_in 2 , for generating a combined signal, in order to widen the dynamic interval and obtain an optimized compromise with the signal-to-noise ratio, preventing undesirable clicks, pops, and fading. 
         [0035]    In detail, the combination here uses the value of an intensity (loudness) signal L that is correlated to a sensing signal, preferably to the first sensing signal S_in 1 , and is compared with a plurality of thresholds, variable as a function of the intensity signal L. In  FIG. 1  there are four different thresholds, forming two lower thresholds and two upper thresholds, referred to hereinafter also as a first lower threshold TH — 1L, a second lower threshold TH — 1H, a first upper threshold TH — 2L, and a second upper threshold TH — 2H, with TH — 1L&lt;TH — 1H&lt;TH — 2L&lt;TH — 2H. These thresholds are illustrated in  FIG. 3  and are used for calculating a reconstructed signal S_R as follows: 
         [0036]    when, starting from an intermediate value comprised between TH — 1L and TH — 2L, the intensity signal L increases until it exceeds the second upper threshold TH — 2H, the second sensing signal S_in 2  is selected (stretch A of the curve of  FIG. 3 ); 
         [0037]    when, starting from an intermediate value comprised between TH — 2H and TH — 1H, the intensity signal L decreases until it drops below the first lower threshold TH — 1L, the first sensing signal S_in 1  is selected (but for an attenuation or reduction of gain, as explained in detail hereinafter), (stretch B of the curve of  FIG. 3 ); 
         [0038]    when the intensity signal L has a value comprised between the first lower threshold TH — 1L and the second upper threshold TH — 2H, without exceeding these thresholds, a signal is selected, indicated in  FIG. 3  as combined signal S_C resulting from a combination of the first and second sensing signals S_in 1 , S_in 2  (stretch C of the curve of  FIG. 3 ). 
         [0039]    In practice, the system works on the basis of a hysteresis that tends to reduce the number of switchings, maintaining the sensing signal or the combination that had been selected previously even beyond the value of the (lower or upper) threshold that determines switching in the opposite direction. In this way, but for a final level adaptation, as explained hereinafter, the interface  1  generates a reconstructed signal S_R as illustrated in  FIG. 2  having an increased dynamic, which ranges from the minimum sound pressure level (SPL) detectable by the first detection structure  2   a,  which is more sensitive to the low sound waves, to the maximum sound pressure level (SPL) detectable by the second detection structure  2   b,  which is more sensitive to high sound waves. 
         [0040]    Furthermore, in the present interface, the combination of the first and second sensing signals S_in 1 , S_in 2  is made using a non-linear factor or weight of a self-adaptive type that enables slow and smooth switching between the first and second sensing signals S_in 1 , S_in 2  and the combined signal. 
         [0041]    Then, in the present interface, the combined signal S_C thus obtained is amplified or attenuated using a variable gain for recovering the original amplitude of the low/high signal, thus preventing saturation. To this end, in the implementation represented in  FIG. 1 , an expander amplifies the combined signal if this is lower than an amplification threshold and, after this amplification threshold, reduces the amplification gain linearly, down to zero at the full scale value. 
         [0042]    With reference once again to  FIG. 1 , the interface  1  has a first and a second input  1   a    1   b,  configured to receive the first and second sensing signals S_in 1 , S_in 2 , respectively, directly from the acoustic transducer  2 , and an output  1   c,  supplying an output signal S_O. 
         [0043]    The electronic interface  1  comprises a first filtering element  5  connected to the first input  1   a;  a first intensity detector  6 , connected to the output of the first filtering element  5 ; a first level adapter  7 , connected to the first input  1   a;  a signal reconstructor  8 , connected to the outputs of the first intensity detector  6  and of the first level adapter  7  and to the second input  1   b  of the interface; a second filtering element  10  connected to the second input  1   b  of the interface; a second intensity detector  11 , connected to the output of the second filtering element  10 ; and a second level adapter  15 , connected to the output of the signal reconstructor  8  and to the output of the second peak detector  11 . The signal reconstructor  8  and the second level adapter  15  form together a recombining engine  16 . 
         [0044]    The first level adapter  7  has the function of reducing the level of the first sensing signal S_in 1  by a reduction or attenuation value ΔS for generating a first adapted sensing signal S_in 1   d  having, for a sound signal picked up with a sound pressure level of 94 dBSPL, an amplitude equal to that of the second sensing signal S_in 2  (in the example represented in  FIG. 2 , thus, ΔS=20 dB). The signal reconstructor  8  then receives, on two signal inputs  8   a,    8   b  of its own, the adapted sensing signal S_in 1   d  and the second sensing signal S_in 2 . 
         [0045]    The first filtering element  5  has the purpose of reducing the variation rate of the first sensing signal S_in 1  and thus simplifying processing; it may be formed by any element suited for this purpose. For instance, in a software implementation of the electronic interface  1 , the first filtering element  5  may be formed by an element computing the RMS (Root Mean Square) value. A first filtered signal S_f 1  is thus present at output of the first filtering element  5  and supplied to the first intensity detector  6 . The first intensity detector  6  is substantially a peak detector, which thus outputs a first peak signal P 1 , used by the signal reconstructor  8  as described hereinafter. 
         [0046]    In the embodiment of  FIG. 9 , the signal reconstructor  8  does not actually generate the four thresholds TH — 1L, TH — 1H, TH — 2L and TH — 2H described above, but calculates two dynamic thresholds, a lower dynamic threshold TH 1  and an upper dynamic threshold TH 2 , the value whereof is dynamically and repeatedly calculated for reproducing the above hysteresis behavior described with reference to  FIG. 3 , as disclosed in detail hereinafter. 
         [0047]    In the embodiment of  FIG. 1 , the signal reconstructor  8  is basically made up of three parts: an adder  20 , which receives the adapted sensing signal S_in 1   d  and the second sensing signal S_in 2  and generates a weighted combination thereof, referred to previously (and in  FIG. 3 ) as combined signal S_C; a selector  21 , which makes the selection referred to above and then outputs the reconstructed signal S_R according to the criteria set forth above; and a control portion  22 , which controls the selector  21  and generates a combination factor β for the adder  20 . For instance, the adder  20  may generate the combined signal S_C as: 
         [0000]        S   —   C=S _in1 d ·(1−β)+ S _in2*β
 
         [0048]    The control portion  22  comprises an equalizer  25 , a threshold computing unit  28  (see  FIG. 9 ), a comparator  26 , and a weight generator  27 . 
         [0049]    In detail, the equalizer  25  is formed by a filter having the task of further reducing the variation rate of the signal to be compared with the switching thresholds (intensity signal L). In particular, the equalizer  25  reacts rapidly while the sound signal increases, but more slowly when the picked up sound signal drops, and thus introduces a delay in this phase. For instance, the equalizer  25  may execute the operations illustrated in  FIG. 5 , namely: 
         [0050]    it resets a previous peak value TsLP to a value K 1  (step  50 ); 
         [0051]    it calculates a peak decay value TsAPF reducing the previous peak value TsLP by a decay value K 2  (step  52 ); 
         [0052]    it calculates the new sample of the intensity signal L as maximum between the absolute value of the sample of the first peak signal P 1  and the previous peak value TsLP (step  54 ); and 
         [0053]    it updates the new previous peak value TsLP so that this is equal to the new sample of the intensity signal L (step  56 ). 
         [0054]    This cycle is repeated for each sample of the first peak signal P 1 , and then the process returns to step  52 . In  FIG. 9 , the control portion  22  comprises, in addition to the equalizer  25 , to the comparator  26 , and to the weight generator  27 , a threshold computing unit  28 . The threshold computing unit  28  calculates the dynamic thresholds described above, executing the operations illustrated in  FIGS. 6A and 6B . 
         [0055]    In detail, for calculating the lower dynamic threshold TH 1  ( FIG. 6A ), the threshold computing element  28 : 
         [0056]    initially sets the lower dynamic threshold TH 1  to the first upper threshold TH — 1H (step  60 ); 
         [0057]    if the current combination factor β is equal to 0 (output YES from verification step  61  of the value of β, which means that now the reconstructed signal S_R is in stretch B of the curve of  FIG. 3 ), sets the lower dynamic threshold TH 1  to the second lower threshold TH_ 1 H (step  62 ); 
         [0058]    if the combination factor β is other than 0 (output NO from step  61 ; i.e., now the reconstructed signal S_R is in stretch C of the curve of  FIG. 3 ), sets the lower dynamic threshold TH 1  to the first lower threshold TH — 1L (step  64 ). 
         [0059]    For calculation of the upper dynamic threshold TH 2  ( FIG. 6B ), the threshold computing unit  28 : 
         [0060]    initially sets the upper dynamic threshold TH 2  to the second upper threshold TH_ 2 H (step  70 ); 
         [0061]    if the combination factor β is equal to 1 (output YES from the verification step  71 ; i.e., the reconstructed signal S_R is in stretch A of the curve of  FIG. 3 ), sets the upper dynamic threshold TH 2  to the second lower threshold TH — 2L (step  72 ); 
         [0062]    if the combination factor β is other than 1 (output NO from step  71 ; i.e., the reconstructed signal S_R is in stretch C of the curve of  FIG. 3 ), sets the upper dynamic threshold TH 1  to the second upper threshold TH_ 2 H (step  74 ). 
         [0063]    According to an embodiment of the present device, the combination factor β generated by the weight generator  27  is not fixed, but is a variable self-adaptive value so that the combined signal S_C follows the dynamic of the input signal without discontinuity and has a value close to that of the adapted sensing signal S_in 1   d  when the intensity signal L has exceeded the first upper threshold TH — 1L and a value close to that of the second sensing signal S_in 2 , when the intensity signal L has dropped below the second lower threshold TH — 2L. 
         [0064]    For instance, the combination factor β is recalculated for each sample as follows (see  FIG. 7 ): 
         [0065]    initially, the intensity signal L is compared with the upper dynamic threshold TH 2  (step  80 ); 
         [0066]    if L≧TH 2 , the combination factor β is set to 1 (step  82 ); 
         [0067]    otherwise, the weight generator  28  verifies whether the intensity signal L is lower than or equal to the lower dynamic threshold TH 1  (step  84 ); 
         [0068]    if it is, the combination factor β is set to 0 (step  86 ); 
         [0069]    if it is not, the distance between the upper dynamic threshold TH 2  and the lower dynamic threshold TH 1  is calculated (step  88 ) and the combination factor β is set to the normalized distance between the value of the intensity signal L and the lower dynamic threshold TH 1  (step  89 ). 
         [0070]    The comparator  26  receives the upper dynamic threshold TH 2 , the lower dynamic threshold TH 1  and the value of the intensity signal L and generates a digital switching signal S 1  supplied to a control input of the selector  21 , which thus outputs the reconstructed signal S_R. The reconstructed signal S_R thus generated is supplied to the second level adapter  15 , which amplifies it for recovering the original intensity, reduced on account of the first level adapter  7 , but only for the portion due to the first sensing signal S_in 1 . 
         [0071]    To this end, the intensity of the input signal is measured using the second sensing signal S_in 2 , since the latter contains the information regarding the high part of the sound signal picked up by the transducer  2 , which is not to be amplified. 
         [0072]    In detail, the second input  1   b  of the electronic interface  1  is connected to the second filtering element  10 , which may be made substantially in the same way as the first filtering element  5  and may be formed by an RMS calculation element. The second filtering element  10  thus outputs a second filtered signal S_f 2 , supplied to the second intensity detector  11 . The second intensity detector  11 , forming substantially a peak detector, outputs a second peak signal P 2 , supplied to the second level adapter  15  to determine the level of gain intended for the reconstructed signal S_R. 
         [0073]    The second level adapter  15  operates substantially as an amplifier of the reconstructed signal S_R, which has a constant gain ΔS (thus equal to the reduction of the first level adapter  7 , in the example equal to 20 dB) up to a certain level of the input signal (here up to 120 dBSPL, maximum level of the first sensing signal S_in 1 ) and then decreases. 
         [0074]    In an embodiment of the present device, in the above second interval, the amplitude of the reconstructed signal S_R is reduced linearly down to zero at the maximum detectable level (in the example considered 140 dBSPL). 
         [0075]    According to a different embodiment, in this second interval, a maximum gain of the reconstructed signal S_R is reduced linearly to zero at the maximum detectable level (in the example considered, 140 dBSPL). In practice, in this case, when the second sensing signal S_in 2  exceeds 120 dBSPL, the second level adapter  15  calculates the maximum gain on the basis of the following law: 
         [0000]        G max=min(Δ S,  140 dBSPL− P 2)
 
         [0000]    Gmax represents the maximum gain that may be applied to the output signal without the latter undergoing any saturation or—in other words—without the latter being amplified beyond what is allowed by the residual dynamic of the system (headroom). 
         [0076]    According to an embodiment of the present device, in order not to introduce sharp alterations in the dynamic of the output signal S_O, the gain G actually applied to the reconstructed signal S_R is calculated in an adaptive way that depends upon the maximum gain Gmax. In particular, the gain G follows two different dynamics according to whether it is increasing or decreasing (and thus the second sensing signal S_in 2  and the reconstructed signal S_R are decreasing or increasing). 
         [0077]    Specifically, here, the gain is increased slowly according to a preset constant, and is decreased in a faster way according to a value linked to the amount of reduction of the maximum gain, implementing a sort of exponential decay. For instance, in the second range of values, the gain G is calculated as illustrated in  FIG. 8 . 
         [0078]    In the example of  FIG. 8 , the second level adapter  15  carries out the following operations: 
         [0079]    it initializes a delay counter D to zero (step  90 ); 
         [0080]    it verifies whether the value of the gain G is lower than the maximum gain GMAX corresponding to the current value of the second sensing signal S_in 2  (or of an average of a certain number of samples) (step  92 ); 
         [0081]    if G&lt;GMAX, it increments the delay counter D (step  94 ); 
         [0082]    it verifies whether the delay counter D has already reached the intended maximum value (step  96 ); 
         [0083]    if it has not, it returns to step  92 ; 
         [0084]    if it has, it resets the delay counter D (step  98 ), and increments the gain G by a step-up value SU (step  100 ), and returns to step  92 ; 
         [0085]    if G is at least equal to GMAX (calculated at the current value or at a value that is an average of a certain number of samples of the second sensing signal S_in 2 ), output NO from step  92 , it verifies whether G&gt;GMAX (step  102 ); 
         [0086]    if it is not (i.e., G=GMAX), it returns to step  92 , without modifying the value of the gain; 
         [0087]    if it is (i.e., the second sensing signal S_in 2  is decreasing), it calculates a step-down value SD linked to the increase rate of the second sensing signal S_in 2  (and thus the decrease rate of the maximum gain GMAX) according to the equation SG=K 3 +(G−GMAX)/K 4 , where K 3  and K 4  are constant (step  104 ); 
         [0088]    it increments the gain G by the step-down value SD (step  106 ), and returns to step  92 . 
         [0089]    The interface described herein has numerous advantages. 
         [0090]    The use, during reconstruction of the signal, of a number of thresholds that take into account the dynamic of the picked up sound signal, with a hysteresis behavior, reduces the number of switchings between the used signals and thus the onset of artefacts and disturbance, such as, in the acoustic field, clicks, pops, or fading. 
         [0091]    The reduction of artefacts and disturbance, for an increase of the dynamic interval of reproduction of the picked up signal, is enhanced by the other measures implemented by the present interface. In particular, the process of repeated filtering of the low signal (first sensing signal S_in 1 ) to obtain the intensity signal L that is used for comparison with the reconstruction thresholds of the signal is advantageous since also this solution contributes to reducing repeated switchings at a short distance, as likewise the non-linear dependence of the gain G effectively applied to the reconstructed signal S_R in the high value area. 
         [0092]    The above improved behavior is also due to the use of self-adaptive weights in the generation of the combined signal S_C, which cause the reconstructed signal S_R to move without discontinuity and smoothly from the previous values to the subsequent ones in all operating conditions. In this way, thanks to the ensemble of solutions described above, even when the picked up signal has sudden level variations, difficult to predict, it is possible to completely eliminate the artefacts, at the same time guaranteeing a wide dynamic interval and high definition. 
         [0093]    The final level adapter or expander  15  moreover ensures complete recovery of the amplitude of the picked up signal, at the same time preventing saturation of the output. The output signal thus obtained, where just the lower values are amplified and amplification of the higher values is gradually reduced, limits the presence of noise in the output signal in so far as this is not amplified in a troublesome way for the samples having a higher level. 
         [0094]    Finally, it is clear that modifications and variations may be made to the interface and to the reconstruction method described and illustrated herein, without thereby departing from the scope of the present disclosure, as defined in the attached claims. 
         [0095]    For instance, the interface may work in a dual way for alignment of the signals at the input of the signal reconstructor  8 . A solution of this type is illustrated by way of example in  FIG. 4 , which shows an interface altogether similar to that of  FIG. 1 , except for the fact that the signal reconstructor  8  receives at input the first sensing signal S_in 1  and a second adapted sensing signal S_in 2   d  obtained by amplifying by ΔS the second sensing signal S_in 2  (via a third level adapter, here an amplifier  30 , arranged between the second input  1   b  and the signal reconstructor  8 ). Furthermore, in this embodiment, the output from the signal reconstructor  8  is connected to a fourth level adapter  15 ′, which operates opposite to the second level adapter  15  of  FIG. 1 ; i.e., it maintains the level of the combined signal S_R up to a certain value (for example, the maximum level of the first sensing signal S_in 1 ) and then reduces the gain (or the maximum gain) linearly down to −ΔS at the maximum level of the second sensing signal S_in 2 . 
         [0096]    The measurement branch of the intensity signal L may be coupled to the second input  1   b  and the measurement branch of the control signal of the second adapter element  15 ,  15 ′ may be coupled to the first input  1   a,  even though the embodiments described above have the advantage of optimally exploiting the information associated to the first and second sensing signals S_in 1 , S_in 2 . 
         [0097]    In the examples described above, the control portion  22  works on two dynamic thresholds, the value whereof is automatically calculated for each signal sample or every n signal samples for having in practice four thresholds. According to yet another embodiment, illustrated in  FIG. 10 , the control portion may use three thresholds, thereby the thresholds TH — 1H and TH — 2L of  FIG. 1  become the same. In all cases, the thresholds are programmable in an initial setting step. 
         [0098]    Furthermore, even though the threshold computing unit  28  and the weight generators  27  have been described as different entities, they may be implemented by a same logic unit, possibly as separate routines. Likewise, the adder  20  and the selector  21  may be implemented by a single reconstructed signal generator S_R. 
         [0099]    The present interface may be used for processing audio signals both of a digital type and of an analog type. 
         [0100]    Furthermore, as has been mentioned, the described solution may be usefully applied to signals detected by dual sensors, including non-acoustic ones. The method proposed for managing two signals with different sensitivity in order to create one with greater dynamic interval may in fact be used for different applications, such as for example MEMS inertial sensors, thermal sensors, or pressure sensors, environmental sensors, chemical sensors, etc. In these cases, the availability of elements with different sensitivity may exploit the advantage of the described interface and method, for supplying more precise information and over a more extensive range of values, without introducing artefacts or alterations in the treated signal. 
         [0101]    The various embodiments described above can be combined to provide further embodiments. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.