Patent Publication Number: US-2022227308-A1

Title: Systems and methods for a piezoelectric diaphragm transducer for automotive microphone applications

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present disclosure is a divisional of and claims priority to and the benefit of U.S. application Ser. No. 16/879,147, which claims priority to and the benefit of (i) U.S. Provisional Application No. 62/895,772, filed Sep. 4, 2019, (ii) U.S. Provisional Application No. 62/939,979, filed Nov. 25, 2019, and (iii) U.S. Provisional Application No. 62/988,625, filed Mar. 12, 2020, all of which are hereby incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     Traditional microphones are used in automotive control systems to provide input for various automotive operations. Traditional microphones, however, may be susceptible to weather conditions when configured outside of a vehicle. More so, traditional microphones may be susceptible to environmental conditions, such as heat or cold, when configured in certain locations on a vehicle, such as in the engine compartment. Therefore, there is a need for a more robust assembly capable of functioning as a microphone for a vehicle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description is set forth with reference to the accompanying drawings. The use of the same reference numerals may indicate similar or identical items. Various embodiments may utilize elements and/or components other than those illustrated in the drawings, and some elements and/or components may not be present in various embodiments. Elements and/or components in the figures are not necessarily drawn to scale. Throughout this disclosure, depending on the context, singular and plural terminology may be used interchangeably. 
         FIG. 1  depicts a piezoelectric diaphragm transducer apparatus adhered to a resonating surface according to example embodiments of the present disclosure. 
         FIG. 2  depicts a piezoelectric diaphragm transducer apparatus adhered to a resonating surface having a printed circuit board (PCB) configured as a tunable mass according to example embodiments of the present disclosure. 
         FIG. 3  depicts a piezoelectric diaphragm transducer apparatus adhered to a resonating surface having a PCB integrated within a housing wall of the apparatus according to example embodiments of the present disclosure. 
         FIG. 4A  depicts a piezoelectric diaphragm transducer apparatus adhered to a resonating surface, where the piezoelectric transducer apparatus includes a PCB integrated within an electrically shielded housing wall of the apparatus according to example embodiments of the present disclosure. 
         FIG. 4B  depicts a piezoelectric diaphragm transducer apparatus adhered to a resonating surface, where the piezoelectric transducer apparatus includes a two-piece housing and annular ring configuration according to example embodiments of the present disclosure. 
         FIG. 5  schematically depicts an example PCB circuit for any one of the apparatuses depicted in  FIGS. 1-4B  according to example embodiments of the present disclosure. 
         FIG. 6  is a view of a rigid connection surface for a flexible diaphragm portion of the apparatus according to example embodiments of the present disclosure. 
         FIG. 7  is a schematic of an example vehicle control system configured to receive a sound input signal from the apparatus(s) depicted in any one of  FIGS. 1-5  in accordance with the present disclosure. 
         FIG. 8A  is a front view of a rear-view mirror with a transducer assembly adhered to an inside surface of the mirror glass according to embodiments of the present disclosure. 
         FIG. 8B  is a partial section view of the rear-view mirror of  FIG. 8A  in accordance with embodiments of the present disclosure. 
         FIG. 9  depicts example transducer assemblies rigidly adhered to vehicle surfaces, according to example embodiments of the present disclosure. 
         FIG. 10  shows a section view of one example configuration for attaching a transducer assembly to an exterior surface of automotive glass beneath a glass bezel of a vehicle, according to an embodiment of the present disclosure. 
         FIG. 11A  depicts an exploded view of a piezoelectric diaphragm transducer apparatus according to example embodiments of the present disclosure. 
         FIG. 11B  depicts a section view of a piezoelectric diaphragm transducer apparatus according to example embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Overview 
     Systems and methods for a transducer assembly for a vehicle having a resonating surface (such as a window or other vehicle surface) are described herein. In some instances, the transducer assembly may include a piezo crystal accelerometer configured as an input device for transforming sound related vibratory input from a rigid resonating surface of the vehicle into an electrical output. The output may include a sound signal that may be processed into a recreation of the original sound using a processing computer, such as, for example, a voice recognition system associated with an automotive computer of the vehicle. One example embodiment includes a mountable, acoustically efficient transducer assembly that can capture sound from a vehicle exterior with sound quality sufficient for voice recognition processing using the onboard computer systems, while having a relatively low noise profile associated with the signal. 
     The transducer assembly may be configured to act as a weather-resistant solid-state microphone device that is mountable on a vehicle interior or exterior and in locations that may normally/typically be unsuitable for microphones or other input devices, such as the engine compartment. The transducer assembly may include a piezoelectric actuator, such as the type conventionally used in small consumer electronics to produce beeps, chirps, or other sound output. The piezoelectric actuator may be configured as an input device, where the transducer assembly is rigidly mountable to the resonating surface, such as an automobile window, and uses the window to receive sound vibrations and produce a sound signal for processing by the automotive computer. 
     In some instances, the transducer assembly may include a small cavity between the piezoelectric device and the glass surface upon which the transducer assembly is mounted. The air gap formed by the cavity may receive kinetic movements caused by sound resonating through the glass. The piezoelectric element may receive these kinetic (in some instances minute) movements via the air gap between the piezoelectric element and the resonating glass surface, such that the piezoelectric element may move freely responsive to the kinetic movements. The piezoelectric element may sense vibration associated with sound (e.g., a person speaking, a dog barking, an engine noise, a street noise, etc.), as the sound resonates through the mounting surface (e.g., the automotive glass) and moves the piezoelectric element, which produces a signal output without interference from a contacting surface that spans across the entire bottom of the piezoelectric element. 
     In this manner, the piezoelectric element may be disposed on a flexible diaphragm suspended just above the air gap by way of a connecting surface (such as a spacer) that extends around a periphery of the flexible diaphragm. The rigid piezoelectric disk portion may receive the air pressure differential forces from the physical manifestation of sound as it propagates through the resonant surface. The piezoelectric element may generate an electrical impulse, which may be conditioned by way of bandpass filters and amplification circuits. The outputs may include a conditioned electric sound signal that may be usable by processing computers onboard the vehicle. 
     The transducer assembly may be electrically passive, such that it is mountable to an exterior vehicle surface and generates a low voltage signal having negligible electromagnetic interference that would otherwise distort or interrupt a sound output signal. For example, the transducer assembly may include electromagnetic shielding in the assembly housing that is configured to shield the low-voltage signals from crosstalk between the device and other electromagnetic forces. 
     The systems and methods described hereafter may provide a weather-resistant and robust sound input apparatus for delivering high-quality sound output signals that mimic a microphone, while using a robust and inexpensive package of solid-state components. These and other advantages of the present disclosure are provided in greater detail herein. 
     Illustrative Embodiments 
     The disclosure will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the disclosure are shown, and not intended to be limiting. 
       FIG. 1  depicts a transducer assembly  100  according to example embodiments of the present disclosure. The transducer assembly  100  may include a transducer housing  102  and an annular spacer  112  configured to rigidly connect with a resonating surface  116  by way of an adhesive layer  114  at the base of the annular spacer  112 . The transducer assembly  100  may further include a flexible diaphragm  136  that divides an interior portion  106  from a cavity  109  formed by the annular spacer  112  when the annular spacer  112  is rigidly disposed in connection with an exterior portion  148  of the resonating surface  116 . The flexible diaphragm  136  may therefore be suspended above the resonating surface  116  such that an air gap  144  is formed between the flexible diaphragm  136  and the resonating surface  116 . Although depicted as generally dome-shaped, it is possible that the housing and general shape of the transducer assembly  100  may be configured as generally rectangular, ovaloid, or another suitable shape. 
     In one embodiment, a piezoelectric disk assembly  133  may include the flexible diaphragm  136  and a piezoelectric disk portion  134 . The piezoelectric disk portion  134  may be rigidly disposed on an interior-facing side of the flexible diaphragm  136  (e.g., on the interior portion  106  side of the flexible diaphragm  136 ). The piezoelectric disk assembly  133  may further include a tunable mass  138  disposed on a top surface of the piezoelectric disk portion  134 . The tunable mass  138  may rigidly connect with the top surface of the piezoelectric disk portion  134  and be sized to a mass that can provide vibrational enhancement to the piezoelectric disk portion  134 . In some instances, the tunable mass  138  may be configured to accentuate movement caused by sound resonating through the resonating surface and through the annular spacer  112  to the flexible diaphragm  136 . 
     Those skilled in the art will appreciate that a tunable mass may be sized, shaped, and oriented within a transducer assembly, where the size, shape, and orientation are based on experimental observation of how these characteristics may affect the system response. The orientation, shape, size, substrate material, density, and fastening means of the tunable mass may be selected so as to enhance vibratory components of the movable member in the transducer assembly  100  by increasing an amplitude of the signal output by the piezoelectric disk portion  134  (and the transducer assembly  100  in general). 
     The transducer assembly  100  may further include an electromagnetic field (EMF) shield layer  118  disposed on a housing interior surface  108  such that the interior portion  106  has electromagnetic separation from an exterior portion  104  of the transducer assembly  100  and the interior portion  106 . The EMF shield layer may include and/or be constructed of conductive or magnetic materials that can electrically isolate a printed circuit board (PCB)  120 , connecting wires  122 ,  124 , and  126 , and the piezoelectric disk portion  134  from radio frequency electromagnetic radiation. For example, the EMF shield layer  118  may be constructed of sheet metal, metal foil, metallic ink, magnetic material, or another suitable material. 
     In some instances, the housing  102  and the EMG shield layer  118  may be integrated as a single unit where the EMF shield layer  118  is over-molded as an insert during an injection mold operation. In other instances, the EMG shield layer  118  may be adhered to the housing interior surface  108  using fastening means that provide a rigid connection between the EMF shield layer  118  and the housing  102 . The EMF shield layer and the housing  102  may be, alternatively, integrated as the same part such that the EMF shielding  118  is an additive component of the thermoplastic used to mold the housing  102  (e.g., a magnetic or metallic powder, etc.). The EMG shield layer  118  may reduce and/or substantially remove the coupling of radio waves, electromagnetic fields, and/or electrostatic fields to the signal output of the PCB  120 . 
     The printed circuit board (PCB)  120  of the transducer assembly  100  may be configured to include one or more signal conditioning circuits that remove signal content that could interfere with output processing. The one or more signal conditioning circuits may also be configured to amplify signal output voltages for transmission to an automotive computer or the like. An example circuit for the PCB  120  is discussed below with reference to  FIG. 5 . 
     Various configurations for placement of the PCB  120  are discussed in  FIGS. 1-4 , which may provide various benefits, including simplification of the assembly, cost reduction, and longevity of the apparatus when used in the field. For example,  FIG. 1  depicts the PCB  120  disposed on the interior portion  106  side of the EMF shield layer  118 . In  FIG. 2 , a PCB  220  is shown disposed on a top surface of a piezoelectric disk portion  234  (in place of the tunable mass, where the PCB  220  is weighted according to the particular application to function also as the tunable mass). In  FIG. 3 , a PCB  320  is integrated into a housing  302  of a transducer assembly  300 , where the housing  302  may include EMF shielding material as an additive molding component and/or where the PCB  320  is sandwiched between the housing  302  and an EMF shield layer  318 . In  FIG. 4 , a PCB  420  may be insert molded into an EMF shield layer  418 , where the EMF shield layer  418  is a separate layer that is rigidly disposed in connection with a housing  402 . 
     Although the advantages for these various configurations are discussed in greater detail in  FIGS. 2, 3, and 4 , respectively, it should be appreciated that in all examples, the PCB may be disposed in communication with an automotive computer or the like by way of a wiring harness  130  or the like, as depicted in  FIG. 1 . For example, the wiring harness  130  may be connectible with the automotive computer. In some instances, the wiring harness  130  may include and/or be a pigtail-less, male, two-pin connector to prevent loose wiring from a pigtail that has the potential to vibrate against adjacent members during vehicle motion. Mechanical contact can be perceived as structure-borne sound and may overload the output signal transmitted from the transducer assembly  100  via the pigtail. Accordingly, the wiring harness  130  may include harness terminals  128  for removably connecting the connector  132  and electrically connecting the PCB  120  with the automotive computer. The harness terminals  128  may connect with the PCB  120  via the connecting wires  126 . The PCB  120  may receive sensor data from the piezoelectric disk assembly  133  by way of the connecting wires  122  and  124 . 
     The transducer assembly  100  is configured such that the annular spacer  112  creates the air gap  144  between the piezoelectric disk assembly  133  and the resonating surface  116 . The annular spacer  112  may be a generally cylindrical spacing ring that can be constructed from a rigid material having relatively low damping characteristics, such as, for example, a rigid polymer, a rigid polymer having a fiber, glass, or other additive, metal, or other suitable material, that allows efficient vibration transfer from the resonating surface  116  to reach the piezoelectric disk assembly  133 . Using softer materials for the annular spacer  112  may attenuate the structure-borne vibration signal and reduce the electrical output and increase noise. The annular spacer may space the assembly housing  102  and flexible diaphragm  136  apart from the mounting surface (e.g., the automotive glass, represented by the resonating surface  116 ) by creating the air gap between the glass (e.g., resonating surface  116 ) and the piezoelectric disk portion  134 . 
     The flexible diaphragm  136  may be constructed of an elastically deformable material, such as, for example, copper, nickel alloy, or another suitable material. In one aspect, portions of the piezoelectric disk assembly  133  may be a commercially available device, such as a piezoelectric diaphragm that may be used commercially as a sound output device for electronics, such as clocks, calculators, digital cameras, alarm systems, etc. For example, the flexible diaphragm  136 , the piezoelectric disk portion  134 , and the connecting wires  122  and  124  may be commercially available and inexpensive piezoelectric diaphragm sound devices that are frequently used for sound generation in electronics. 
     The piezoelectric disk assembly  133  may be configured above the resonating surface  116  with the air gap  144  separating the diaphragm from the resonating surface  116 . By mounting the piezoelectric disk assembly  133  to the annular spacer  112  at a rigidly connected annular edge  140 , a rigid connection surface  142  may form part of the enclosed air gap  144  that increases the sensitivity of the piezoelectric disk portion  134  as it responds to kinetic input (e.g., vibration with sound) resonating through the resonating surface  116 . 
     In some instances, the piezoelectric disk assembly  133  may include a commercially available piezoelectric sound component rigidly fixed to the annular spacer  112  with fastening means, such as, for example, a double-sided adhesive layer, epoxy, or a mechanical connection by way of a press fit between the rigid connection surface  142  and an annular bottom edge of the EMF shield layer  118 . 
     The annular spacer  112  may be separate from the housing  102 . That is, the annular spacer  112  may connect to the housing  102  using a snap fit feature that rigidly fastens the annular spacer  112  to the housing  102  such that the piezoelectric disk assembly  133  is sandwiched between the two mating parts. Other means for connection are possible and are contemplated. Regardless of the method of connecting the annular spacer  112 , the housing  102 , and the piezoelectric disk assembly  133 , it should be appreciated that the connecting means provide the rigid connecting surface  142  at a periphery of the flexible diaphragm  136  at an outer edge, such that the diaphragm  136  is distanced from the mounting surface of the resonating surface  116 . These features may create the secure connections for transmitting vibratory signals to the piezoelectric disk portion  134 , with enhanced sensitivity by way of the air pressure differential associated with the vibrations acting on the air gap  144 . In some instances, the housing and the spacer may be a single unitary component. 
     The adhesive layer  114  and the rigid connection surface  142  (which may also be an adhesive layer) may provide rigid connection between the flexible diaphragm  136 , the annular spacer  112 , and the resonating surface  116 . The adhesive layer  114  (and in some embodiments, the rigid connecting surface  142 ) may include fastening means, such as, for example, a commercially known permanent double-sided adhesive material, an epoxy bonding agent, a fastener (e.g., screws/bolts) or another means for providing the rigid connection between the flexible diaphragm  136 , the annular spacer  112 , and the resonating surface  116 . 
     The bottom portion of the transducer assembly  100  may be mounted to the resonating surface  116  (which may be, in some embodiments, automotive window glass). It should be appreciated that sensitivity and longevity of the transducer assembly  100  may be enhanced by a corresponding shape or indention in the resonating surface  116  such that a cup-shaped dish within the glass surface provides a receiving surface upon which the transducer assembly  100  may be mounted. For example, the mounting surface may be shaped like a flat circular donut or ring. 
     The PCB  120  may provide band pass filtering via one or more bypass filters and signal amplification via one or more amplification circuits that can filter the signal output and enhance desired frequencies centered on the human voice (e.g., about 150 Hz to about 8 kHz). The PCB  120  may also provide high pass filtering that can reduce the influence of any rigid body motion or vibration associated with vehicle movement by reducing the dynamic range of the structure-borne signal. The PCB  120  may include one or more op-amps that increase the voltage output of the transducer assembly  100 , powered by a phantom voltage charge (similar to those used on traditional ECM microphone circuits), which may increase the signal strength before it travels down through the wiring harness  130  to an automatic speech recognition system associated with an automotive computer. 
     The wiring harness  130  may be integrated with the housing  102  such that the harness and the housing  102  are molded as a single unit, having insert molded harness terminals  128  wired in connection with the PCB  120 . In another example, the PCB  120  may connect with the wiring harness  130  and the harness terminals  128  by way of the connecting wires  126  that extend through openings in the housing  102  for the wires to pass through to the exterior surface  110  and connect with the harness terminals  128 . In such instances, the wiring harness  130  may be a separate component rigidly fastened to the exterior surface  110  of the housing  102  using fastening means, such as an adhesive, plastic welding, mechanical fasteners, or other suitable means. 
     The connector  132  may provide connection between the PCB  120  and the automotive computer. In some instances, the piezoelectric diaphragm transducer assembly  100  may be configured to have a low profile and small package size such that it may be discretely packaged at an edge of an automotive window glass, behind door trim of the automobile, or in another area such that the transducer is completely out of view of the customer. The package may take a low profile (e.g., no more than 20 mm high) and may be configured to include sufficient clearance between the exterior surface  110  of the transducer assembly  100  and any adjacent components of the automobile. Example clearance may be, for example, at least 5 to 10 mm clearance from any surrounding door trim or other component when installed to provide adequate protection from vibratory signal noise and to provide protection from unintended structure-borne noises that may pollute the window microphone signal. 
       FIG. 2  depicts another example piezoelectric diaphragm transducer  200  adhered to the resonating surface  116 . Except where expressly described in the following paragraphs, the transducer assembly  200  may be substantially similar or identical to the transducer assembly  100  as shown in  FIG. 1 . For example, the transducer assembly  200 , as shown in  FIG. 2 , may differ from the assembly  100  of  FIG. 1  in that a piezoelectric disk assembly  233  may be comprised of a piezoelectric disk portion  234 , a flexible diaphragm  236 , and the PCB  220 , of which the piezoelectric disk portion  234  and the PCB  220  are rigidly connected to a top surface of the flexible diaphragm  236 . The flexible diaphragm  236  may be substantially similar or identical to the flexible diaphragm  136  described with respect to  FIG. 1 . The piezoelectric disk portion  234  may also be substantially similar or identical to the piezoelectric disk portion  134  of  FIG. 1 . 
     The transducer assembly  200  may configure the PCB  220  to additionally function as a tunable mass (where the tunable mass  138  as shown in  FIG. 1  is omitted, via weighting the PCB  220  to function as the mass in addition to a signal conditioning unit). In one aspect, the PCB  220  may be weighted by varying a size, thickness, material, or other characteristic, such that the PCB package size, when disposed within the piezoelectric disk assembly  233 , mimics the size and mass distribution of the tunable mass as described in  FIG. 1 . Accordingly, the PCB  220  may be disposed on and rigidly connect with the piezoelectric disk portion  234 . A connecting wire  222  and a connecting wire  224  may connect the PCB  220  with a respective one of the piezoelectric disk portion  234  and the flexible diaphragm  236 . 
     The configuration depicted in  FIG. 2  may provide several advantages, including a reduction of the number of parts in the transducer assembly  200 , which may reduce manufacturing costs, simplify design complexity, and increase part longevity and functional reliability. In other aspects, by integrating the PCB and the tunable mass into a single unit that moves with the piezoelectric disk assembly  233 , the transducer assembly  200  may experience reduced signal noise from external vibrations, because the PCB is decoupled from the housing except through the flexible diaphragm  236 . 
       FIG. 3  depicts another example piezoelectric diaphragm transducer apparatus (hereafter “transducer assembly  300 ”) adhered to the resonating surface  116 . Except where expressly described in the following paragraphs, the transducer assembly  300  may be substantially similar or identical to the transducer assembly  100  as shown in  FIG. 1 . For example, the transducer assembly  300  as shown in  FIG. 3  may differ from the assembly  100  of  FIG. 1  in that a piezoelectric disk assembly  333  may include a piezoelectric disk portion  334 , a flexible diaphragm  336 , and a tunable mass  338 . However, in the example embodiment of  FIG. 3 , a PCB  320  may be included as an integrated part of a housing  302 . In  FIG. 3 , an EMF shield layer  318  is depicted. The EMF shield layer  318  may be separate from (and rigidly connected with) the assembly housing  302 , or alternatively, may be integrated with the housing  302  such that the EMF shield layer  318  is provided as a property of a molding additive and not a separate part distinct from the housing  302 . In this example, the housing  302  may be constructed of a thermoplastic having electromagnetic shielding properties. 
     In another aspect, the PCB  320  may be sandwiched between the EMF shield layer  318  and the housing  302 . This example configuration may provide EMF shielding properties that protect the PCB  320  from EMF external vibrations originating from the exterior surface side of the transducer assembly  300  and may also protect the PCB  320  from EMF originating from the interior portion  306  side of the transducer assembly  300 . For example, EMF vibrations could originate from inside of the vehicle through the resonating surface  116  (which may be glass). 
     The flexible diaphragm  336  may be substantially similar or identical to the flexible diaphragm  136  described with respect to  FIG. 1 . The piezoelectric disk portion  334  may also be substantially similar or identical to the piezoelectric disk portion  134  of  FIG. 1 . 
     The configuration depicted in  FIG. 3  may provide several advantages, including a reduction in parts that are movable in the assembly (which may reduce unwanted signal content caused by movement of the components). Other possible advantages may include a reduction of manufacturing costs associated with removing design complexity and an increase in part longevity in the field. In other aspects, by integrating the PCB to be integral with the housing  302 , the transducer assembly  300  may further enhance signal sensitivity and reduced signal noise from vibrations, because the PCB is integrated with the housing  302  without the need for connecting means and the possibility of micro-movements associated with physical connection of separate members. 
       FIG. 4A  depicts another example piezoelectric diaphragm transducer apparatus (hereafter “transducer assembly  400 ”), where the transducer assembly  400  includes a PCB  420  integrated within an electrically shielded wall of an EMF shield layer  418 . Except where expressly described in the following paragraphs, the transducer assembly  400  may be substantially similar or identical to the transducer assembly  100  as shown in  FIG. 1 . For example, the transducer assembly  400  as shown in  FIG. 4A  may differ from the assembly  100  of  FIG. 1  in that a piezoelectric disk assembly  433  may include a piezoelectric disk portion  434 , a flexible diaphragm  436 , and a tunable mass  438 . 
     The flexible diaphragm  436  may be substantially similar or identical to the flexible diaphragm  136  described with respect to  FIG. 1 . The piezoelectric disk portion  434  may also be substantially similar or identical to the piezoelectric disk portion  134  of  FIG. 1 . 
     In one aspect, the PCB  420  may be insert molded with the EMF shield layer  418 , and the EMF shield layer  418  may be rigidly disposed in connection with the housing  402 . 
     The configuration depicted in  FIG. 4A  may provide several advantages, including a reduction of connecting parts in the assembly, which may reduce manufacturing costs and may provide a reduction in design complexity. Fewer connected parts could also increase part longevity and functional reliability. In other aspects, by integrating the PCB  420  with the housing  402  and/or the EMF shield layer  418 , the transducer assembly  400  may enhance signal sensitivity and achieve reduced signal noise from vibrations, because the PCB is integrated with the housing  402  and/or the shield layer  418 , without the need for connecting means and the possibility of micro-movements associated with physical connection of separate members. 
       FIG. 4B  depicts another example piezoelectric diaphragm transducer apparatus (hereafter “transducer assembly  401 ”), where a housing  403  is disposed rigidly connected with a separate annular ring  412  such that the flexible diaphragm  436  is rigidly sandwiched between the two connected pieces. Although the transducer assembly  401  is depicted with the PCB  420  integrated within an electrically shielded wall of an EMF shield layer  418 , it is possible to apply the two-piece housing and annular ring configuration of  FIG. 4B  to any of the configurations described with respect to  FIGS. 1-4A . 
     Except where expressly described in the following paragraphs, the transducer assembly  400  may be substantially similar or identical to the transducer assembly  100  as shown in  FIG. 1 . For example, the transducer assembly  401  as shown in  FIG. 4B  may differ from the assembly  100  of  FIG. 1  in that the housing  403  is configured to rigidly connect with an annular ring  412 , which may be a separate part from the housing  403 , by fastening means, such as, for example, a snap fit with undercut snap features, a press fit, adhesive bonding, fasteners (e.g., screws/bolts) or another fastening means. 
     The configuration depicted in  FIG. 4B  may provide several advantages including ease of assembly of the transducer assembly  401 , which may reduce manufacturing costs and may provide a reduction in design complexity. In other aspects, by rigidly connecting the housing  403  with the annular spacer  412  as two separate pieces that rigidly sandwich the flexible diaphragm  436  between the members, a conventional piezoelectric diaphragm may be transformed from a sound output device into an input device as described herein. 
       FIG. 5  schematically depicts an example PCB circuit  500  for use with any one of the apparatuses depicted in  FIGS. 1-4B . The PCB circuit  500  can include a disc element circuit  505  and a preamp circuit  510 . In one example, the circuit  500  may include a preamp circuit and bandpass filter. The bandpass filter may provide an output signal having content between 150 Hz to 8 kHz and omit other signal content. The op-amp may increase output voltage such that the circuit  500  may provide a signal to a microphone input circuit  515  having sufficient amplitude to support a clear and unambiguous output that may be used for voice recognition. 
       FIG. 6  is an overhead view  6 - 6  (as noted by the arrows  6 - 6  in  FIG. 1 ) of the flexible diaphragm  136 . View  6 - 6  depicts the rigid connection surface disposed about a peripheral edge of the diaphragm  136  (that mates with the rigidly connected annular edge  140 ). By connecting the flexible diaphragm  136  at the edges only with a secure connecting means that positively transmits vibration to the flexible diaphragm  136 , the connection footprint leaves ample interior space that allows the flexible diaphragm  136  to flex from the air pressure differential created by micro-vibrations through the resonating surface  116 . 
       FIGS. 11A and 11B  depict a piezoelectric diaphragm transducer apparatus  600 , according to example embodiments of the present disclosure. Except where expressly described in the following paragraphs, the transducer assembly  600  may be substantially similar or identical to the transducer assembly  100  as shown in  FIG. 1 . In the transducer assembly  600  as shown in  FIGS. 11A and 11B , the housing  102  may be connected to the annular spacer  112  via an attachment assembly  602 . In some instances, the attachment assembly  602  may not require adhesives to hold the piezoelectric disk assembly  133  between the housing  102  and the annular spacer  112 . Adhesives may cause damping and lessens the vibration transfer from the glass to the piezoelectric disk assembly  133 . Thus, the lack of adhesives may provide the technical advantage of increased functionality and accuracy of the piezoelectric diaphragm transducer apparatus  600 . 
     The annular spacer  112  may include a slot  604 . In some instances, the slot  604  may be annular. For example, the slot  604  may extend around the circumference of the annular base  112 . The slot  604  may be any suitable sized, shape, or configuration. The slot  604  may include a ledge  606  and a wall  608 . In some instances, the ledge  606  and the wall  608  may be transverse to each other. The ledge  606  and the wall  608  may be any suitable size, shape, or configuration. One or more protrusions  610  may extend from the wall  608 . The protrusions  610  may be any suitable size, shape, or configuration. 
     The housing  102  may include a groove  612 . In some instances, the groove  612  may be annular. For example, the groove  612  may extend around an inner circumference of the housing  102 . The groove  612  may be any suitable size, shape, or configuration. The groove  612  may include a ledge  614  and a wall  616 . In some instances, the ledge  614  and the wall  616  may be transverse to each other. The ledge  614  and the wall  616  may be any suitable size, shape, or configuration. One or more channels  618  may be disposed within the wall  616 . The channels  618  may include an open end  620  and a closed end  622 . In some instances, the channels  618  may include a first portion  624  and a second portion  626 , which is traverse from the first portion  624 . That is, the channels  618  may be L-shaped or the like. The channels  618  may be any suitable size, shape, or configuration. 
     The slot  604  of the annular spacer  112  and the groove  612  of the housing  102  may be configured to mate with each other. That is, the slot  604  and groove  612  may complement each other. In this manner, the protrusions  610  may be configured to mate with the channels  618 . For example, a protrusion  610  may pass into a channel  618  through the open end  620  of the channel  618  and move along the first portion  624  of the channel  618  when the housing  102  is pressed against the annular spacer  112 . Next, as the housing  102  is rotated, the protrusion  610  may travel along the second portion  626  of the channel  618 . In some instances, the second portion  626  of the channel  618  may be angled (e.g., as slight incline) such that the housing  102  is tightened against the annular spacer  112  as the housing  102  is rotated onto the annular spacer  112 . For example, the second portion  626  of the channel  618  may be angled away from the annular spacer  112 . In this manner, the protrusion  610  may travel along the second portion  626  of the channel  618 , which may cause the protrusion  610  to apply greater and greater force against the second portion  626  of the channel  618  as the protrusion  610  travels further up and into the second portion  626  of the channel  618 . 
     The piezoelectric disk assembly  133  may be disposed between the housing  102  and the annular spacer  112 . For example, an outer edge  628  of the piezoelectric disk assembly  133  may be sandwiched (i.e., trapped) between the ledge  606  of the annular spacer  112  and the ledge  614  of the housing  102 . In this manner, the piezoelectric disk assembly  133  may be secured in place without the use of adhesives. 
       FIG. 7  depicts a schematic of an example vehicle control system  700  configured to receive a sound input signal from a transducer assembly  745 . The transducer assembly  745  may be substantially similar or identical to any of the transducer assemblies  100 ,  200 ,  300 , or  400 , as described with respect to corresponding  FIGS. 1-4B ). Although described hereafter as an autonomous vehicle, the control system  700  that may be configured for use in a vehicle  705 , which may be an autonomous vehicle, a semi-autonomous vehicle, or a conventionally driven vehicle. The control system  700  can include a user interface  710 , a navigation system  715 , a communication interface  720 , autonomous driving sensors  730 , an autonomous mode controller  735 , and one or more processing device(s)  740 . The control system  700  may further include a voice recognition system  755 . The transducer assembly  745  may provide input signals to the voice recognition system  755 , which may be configured to interpret the input signals to a contextualized voice input. In one embodiment, the control system  700  may perform one or more vehicle actions based on the input, such as starting a drive motor, stopping the vehicle, performing steering or braking actions, or other vehicle operations. 
     The user interface  710  may be configured or programmed to present information to a user during operation of the vehicle  705 . In one aspect, the user interface may provide auditory output of the signal received from the transducer assembly  745 . Moreover, the user interface  710  may be configured or programmed to receive user inputs, and thus, it may be disposed in or on the vehicle  705  such that it may be viewable, audible, or interactive by a passenger or operator. For example, in one embodiment where the vehicle  705  is a passenger vehicle, the user interface  710  may be located in the passenger compartment. 
     The navigation system  715  may be configured and/or programmed to determine a position of the autonomous vehicle  705 . The navigation system  715  may include a Global Positioning System (GPS) receiver configured or programmed to triangulate the position of the AV  705  relative to satellites or terrestrial based transmitter towers. The navigation system  715 , therefore, may be configured or programmed for wireless communication. The navigation system  715  may be further configured or programmed to develop routes from a current location to a selected destination, as well as display a map and present driving directions to the selected destination via, e.g., the user interface  710 . In some instances, the navigation system  715  may develop the route according to a user preference. Examples of user preferences may include maximizing fuel efficiency, reducing travel time, travelling the shortest distance, or the like. 
     In one aspect, the vehicle control system  700  may be configured to receive audio data from the piezoelectric diaphragm transducer  750  (hereafter “transducer  750 ”) and perform one or more vehicle operations based on the audio data. For example, the vehicle control system  700  (hereafter “control system  700 ”) may receive the audio data, where the data includes one or more engine or motor sounds indicative of an automotive maintenance issue that requires imminent attention or servicing. Accordingly, the control system  700  may receive the audio data, compare the audio data to a database of audio sounds correlated with automotive maintenance indications, and determine based on a match of the audio data to a maintenance indication, that the vehicle requires imminent maintenance. Responsive to determining that the vehicle requires imminent maintenance, the control system  700  may control the autonomous mode controller  735  to navigate to a service location or other safe location such that the maintenance issue can be addressed. In one aspect, the control system  700  may obtain information from the navigation system  715  and navigate the vehicle  705  to the service location based on the GPS information. 
     In another aspect, the voice recognition system  755  may receive the audio data and determine that the audio is indicative of human speech. The control system  700  may cause the voice recognition system  755  to recognize the speech content in the audio data and evaluate the speech content for context that indicates an imminent need for a vehicle control action, such as stopping the vehicle, slowing down a velocity of the vehicle, steering the vehicle to a side of the road, etc. 
     The control system  700  may facilitate communication between the driver of the vehicle  705  and another driver. For example, another vehicle may pull up next to the vehicle  705 , and the driver of the other vehicle may initiate an impromptu communication. The driver of the second vehicle may attempt to get the attention of the driver of the vehicle  705 , perhaps by asking for directions with the hope that their voice is heard through the closed window of the vehicle  705 . Although the driver, with windows up, music playing, etc., may not normally be able to hear the second driver&#39;s communication, the voice recognition system  755  may receive the speech input (sound) through the transducer  750 , which may be attached to the automotive glass  760  of the vehicle  705 , and determine, via the voice recognition system  755 , that the speech content of the sound received from the transducer  750  correlates to a need to play an audio feed through the audio system of the vehicle  705 . The control system  700  may output the voice signal by way of the communication interface  720  and/or the user interface device  710 . In this example, although the window is up, a clear recreation of the individual&#39;s voice may sound through the vehicle sound system(s) such that the driver of the vehicle  705  can clearly hear the question being asked by the other driver. 
     In another example, an observer outside of the vehicle may notice that the vehicle operator has left an object (e.g., a cup of coffee) on the roof of the vehicle and has inadvertently begun to drive off with the cup of coffee on the roof. The observer may yell, “Driver! Your coffee is on the roof!” Although the driver may not be able to hear the verbal expression, the control system  700  may receive the audio data via the transducer  750 , interpret the data to contextualize the speech content indicating “coffee on the roof,” compare the context to a database indicative of actions correlated with particular phrases in context (e.g., “coffee on the roof” correlates to a need to slow down and stop the vehicle when safely able to do so), and issue vehicle control commands to the autonomous mode controller  735  based at least in part on the correlated action associated with the phrase that was contextualized by the voice recognition system. 
     The communication interface  720  may be configured or programmed to facilitate wired and/or wireless communication between the components of the vehicle  705  and other devices, such as a remote server or another vehicle when using a vehicle-to-vehicle communication protocol. The communication interface  720  may also be configured and/or programmed to communicate directly from the vehicle  705  to a mobile device using any number of communication protocols such as Bluetooth®, Bluetooth® Low Energy, or Wi-Fi. 
     A telematics transceiver  725  may include wireless transmission and communication hardware that may be disposed in communication with one or more transceivers associated with telecommunications towers and other wireless telecommunications infrastructure. For example, the telematics transceiver  725  may be configured and/or programmed to receive messages from, and transmit messages to one or more cellular towers associated with a telecommunication provider, and/or and a Telematics Service Delivery Network (SDN) associated with the vehicle  705 . In some examples, the SDN may establish communication with a mobile device, which may be and/or include a cell phone, a tablet computer, a laptop computer, a key fob, or any other electronic device. An internet connected device such as a PC, Laptop, Notebook, or Wi-Fi connected mobile device, or another computing device may establish cellular communications with the telematics transceiver  725  through the SDN. 
     The communication interface  720  may also communicate using one or more vehicle-to-vehicle communications technologies. An example of a vehicle-to-vehicle communication protocol may include, for example, a dedicated short-range communication (DSRC) protocol. Accordingly, the communication interface  720  may be configured or programmed to receive messages from and/or transmit messages to a remote server and/or other autonomous, semi-autonomous, or manually-driven vehicles. In some aspects, the transducer  750  may generate a sound signal that is transmitted to another vehicle using the vehicle-to-vehicle communication protocol. 
     The autonomous driving sensors  730  may include any number of devices configured or programmed to generate signals that help navigate the vehicle  705  while the vehicle  705  is operating in the autonomous (e.g., driverless) mode. Examples of autonomous driving sensors  730  may include a radar sensor, a LIDAR sensor, a vision sensor, or the like. The autonomous driving sensors  730  may help the vehicle  705  “see” the roadway and the vehicle surroundings and/or negotiate various obstacles while the vehicle is operating in the autonomous mode. 
     The autonomous mode controller  735  may be configured or programmed to control one or more vehicle subsystems while the vehicle is operating in the autonomous mode. Examples of subsystems that may be controlled by the autonomous mode controller  735  may include one or more systems for controlling braking, ignition, steering, acceleration, transmission control, and/or other control mechanisms. The autonomous mode controller  735  may control the subsystems based, at least in part, on signals generated by the autonomous driving sensors  730 . It is contemplated that the control system  700  may control one or more subsystems using information received from the transducer  750 . Example information may include speech data as described above, vehicle sounds indicative of a mechanical failure or need for maintenance, emergency situations indicated by sounds such as, for example, a siren of an emergency vehicle, and other auditory input. 
       FIGS. 8A and 8B  depict a front view of a rear-view mirror  805  and a partial section view of the rear-view mirror  805 , respectively. The rear-view mirror  805  is configured with a piezoelectric diaphragm transducer  810  (hereafter “transducer assembly  810 ”) that may receive vibrational input from the rear-view mirror glass  820  of the rear-view mirror  805 , and produce a sound signal that may be used for various purposes. The transducer assembly  810  may be substantially similar or identical to the transducer assembly  100  as described with respect to  FIG. 1 . 
     The section view A-A as shown in  FIG. 8B  depicts the transducer assembly  810  on an interior portion  815  of the rear-view mirror  805 . The transducer assembly  810  is depicted rigidly connected with an inside surface  825  of the rear-view mirror glass  820 . In an example embodiment, the transducer assembly  810  may act as the sound input device for use on an interior surface of a vehicle (e.g., inside of a vehicle similar to the vehicle  705  as shown in  FIG. 7 ) such that the transducer  810  may capture sound input through the glass  820 , and transmit the sound input to a connected vehicle computer. The configuration as shown in  FIGS. 8A and 8B  may replace or supplement an interior microphone that is often configured inside the cabin of the vehicle (e.g., where the microphone is integrated with the rear-view mirror, the sun visor, or at another interior location). 
     In some aspects, the transducer assembly  810  may be installed on other non-glass surfaces of a vehicle. For example,  FIG. 9  depicts a vehicle  905  having example transducer assemblies  910 ,  915 ,  920 ,  925 ,  930 , and  935  rigidly adhered to various vehicle surfaces that provide various respective benefits as resonating surfaces. The transducer assemblies  910 - 935  may connect with and be disposed in communication with a vehicle control system  940  via a control bus  945 . The control system  945  may be substantially similar or identical to the control system  700  described with respect to  FIG. 7 . 
     The vehicle control system  940 , in some aspects, may connect with the transducer assembly  910 , which may rigidly connect with an exterior surface of a vehicle windshield  950  beneath a window bezel  955 . One advantage to placing the transducer assembly at a location on the windshield behind a bezel may include taking advantage of a large area of the resonating surface (e.g., the windshield  950 ), which may produce high quality sound signals that originate from a forward position with respect to the vehicle  905 . Accordingly, the sound may resonate through the windshield, with which the transducer assembly  910  may generate an output signal. 
     The control system  905  may be disposed in electrical communication with the transducer assembly  925  configured on the rear-view mirror of the vehicle  905 , which may provide means for sound pickup originating from the side or rear of the vehicle  905 . Moreover, vocal communication from individuals standing outside of the vehicle  905  may be generally level with the transducer assemblies  910 ,  925 ,  930 ,  935 , etc., such that voices are readily received by the resonating surfaces and transducer assemblies attached thereto. 
       FIG. 10  shows a section view of one example configuration for attaching a transducer assembly  1015  to an exterior surface of automotive glass  1005  beneath a glass bezel  1025 . The automotive glass  1005  may include an indexed recess  1010  forming a pocket for mounting the transducer assembly  1015 . The indexed recess  1010  may provide clearance (e.g., clearance  1020 ) between surfaces of the transducer assembly  1015  and any other vehicle members adjacent to the assembly such as, for example, the glass bezel  1025 . Producing clearance may mean that adjacent parts to the transducer assembly  1015  do not contact the transducer assembly  1015 . By providing the recess  1010  in the automotive glass  1005 , the transducer assembly  1015  may be installed at locations of the vehicle that may be out of sight from users and may protect the transducer assembly  1015  from the weather or physical damage due to bumping, etc. It should be appreciated, however, that among the many advantages of embodiments described herein, the transducer assembly  1015  (and other similar transducer assemblies described herein) may function as robust and weather resistant microphones that may be installed on vehicle exterior surfaces because they are generally unaffected by weather, dirt, etc. 
     In the above disclosure, reference has been made to the accompanying drawings, which form a part hereof, which illustrate specific implementations in which the present disclosure may be practiced. It is understood that other implementations may be utilized, and structural changes may be made without departing from the scope of the present disclosure. References in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a feature, structure, or characteristic is described in connection with an embodiment, one skilled in the art will recognize such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. 
     It should also be understood that the word “example” as used herein is intended to be non-exclusionary and non-limiting in nature. More particularly, the word “exemplary” as used herein indicates one among several examples, and it should be understood that no undue emphasis or preference is being directed to the particular example being described. 
     A computer-readable medium (also referred to as a processor-readable medium) includes any non-transitory (e.g., tangible) medium that participates in providing data (e.g., instructions) that may be read by a computer (e.g., by a processor of a computer). Such a medium may take many forms, including, but not limited to, non-volatile media and volatile media. Computing devices may include computer-executable instructions, where the instructions may be executable by one or more computing devices such as those listed above and stored on a computer-readable medium. 
     With regard to the processes, systems, methods, heuristics, etc. described herein, it should be understood that, although the steps of such processes, etc. have been described as occurring according to a certain ordered sequence, such processes could be practiced with the described steps performed in an order other than the order described herein. It further should be understood that certain steps could be performed simultaneously, that other steps could be added, or that certain steps described herein could be omitted. In other words, the descriptions of processes herein are provided for the purpose of illustrating various embodiments and should in no way be construed so as to limit the claims. 
     Accordingly, it is to be understood that the above description is intended to be illustrative and not restrictive. Many embodiments and applications other than the examples provided would be apparent upon reading the above description. The scope should be determined, not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. It is anticipated and intended that future developments will occur in the technologies discussed herein, and that the disclosed systems and methods will be incorporated into such future embodiments. In sum, it should be understood that the application is capable of modification and variation. 
     All terms used in the claims are intended to be given their ordinary meanings as understood by those knowledgeable in the technologies described herein unless an explicit indication to the contrary is made herein. In particular, use of the singular articles such as “a,” “the,” “said,” etc. should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary. Conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments could include, while other embodiments may not include, certain features, elements, and/or steps. Thus, such conditional language is not generally intended to imply that features, elements, and/or steps are in any way required for one or more embodiments.