Patent Publication Number: US-11051094-B2

Title: Interchangeable port acoustical cap for microphones

Description:
FIELD 
     The present disclosure relates generally to microphones, and more particularly to small microphones that may be configured as, for example, lavalier, lapel, clip, body, earset, headset, collar, or neck microphones. These types of microphones can be worn by or attached to a person or instrument. 
     BACKGROUND 
     Microphones convert sound into an electrical signal through the use of a transducer that includes a diaphragm to convert sound into mechanical motion, which in turn is converted to an electrical signal. Generally, microphones can be categorized by their transducer method (e.g., condenser, dynamic, ribbon, carbon, laser, or microelectromechanical systems (MEMS)). 
     One use of a microphone is amplifying a single person or specific instrument, such as in the context of television, theater, public speaking, telemarketing, or a musical performance. In these instances, a user may either hold the microphone or use a microphone stand. An alternative, however, is to attach the microphone to a piece of clothing or the body. Microphones made for this purpose include lavalier, lapel, clip, body, headset, earset, collar, or neck microphones. These microphones may be more mobile and may allow one to use their hands without also having to use a microphone stand. 
     These type of microphones (e.g., lavalier microphones) can also be used with acoustical caps that cover the microphone. These acoustical caps may include holes that allow sound to enter into a resonant cavity that boosts or attenuates certain frequencies and thus changes the frequency response of the sound that the microphone receives. Which frequencies are emphasized and attenuated by the acoustical cap depend on size and shape of the hole(s) or inlet(s) of the acoustical cap as well as the size and shape of the cavity defined by the acoustical cap. This use of the size and shape of a cavity and its inlet(s) to emphasize certain acoustic frequencies is an example of taking advantage of what is commonly known as Helmholtz resonance. In order to change the frequency response of the sound the microphone receives based on recording in different environments, users will alternate between caps that have different sizes of inlets and create different sizes of resonate cavities. 
     BRIEF SUMMARY 
     The following presents a simplified summary of the disclosure in order to provide a basic understanding of some aspects of the disclosure. This summary is not an extensive overview of the disclosure. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. The following summary merely presents some concepts of the disclosure in a simplified form as a prelude to the more detailed description provided below. 
     In one example, a lavalier microphone may include a mechanical enclosure or housing that carries the microphone&#39;s circuitry, including the microphone&#39;s diaphragm. Sound travels to the microphone&#39;s diaphragm through a sound passage that includes an opening in the mechanical enclosure. In this example, the lavalier microphone can be covered by an acoustical cap with at least two inlets and two corresponding cavities. The inlets and their corresponding cavities can form different Helmholtz resonators. When using the lavalier microphone, a user can orient the acoustical cap to align one of the two acoustic passages. Each Helmholtz resonator can be designed to allow the lavalier microphone to receive sounds with different frequency responses, which may allow a user to utilize the same lavalier microphone and with a single acoustical cap for better performance in a variety of different recording circumstances. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present disclosure and the advantages thereof may be acquired by referring to the following description in consideration of the accompanying drawings, in which like reference numbers indicate like features, and wherein: 
         FIG. 1  is a schematic of an example lavalier microphone without an acoustical cap; 
         FIG. 2  is a schematic of the lavalier microphone of  FIG. 1  that includes an acoustical cap in a first orientation relative to the lavalier microphone; 
         FIG. 3  is an example frequency response graph of the example lavalier microphone of  FIG. 1  without an acoustical cap; 
         FIG. 4  is an example frequency response graph of the example lavalier microphone of  FIG. 1  with the cap in the orientation of  FIG. 2 ; 
         FIG. 5  is a schematic of the example lavalier microphone of  FIG. 1  that includes the acoustical cap in a second orientation relative to the lavalier microphone; 
         FIG. 6  is an example frequency response graph of an example lavalier microphone of  FIG. 1  with the acoustical cap in the orientation of  FIG. 5 ; 
         FIG. 7A  is a perspective top view of a lavalier microphone with an acoustical cap in a first orientation relative to the lavalier microphone; 
         FIG. 7B  is a cross-section of the lavalier microphone and acoustical cap in  FIG. 7A ; 
         FIGS. 8A and 8B  are a side view and a cross-section, respectively, of the lavalier microphone with the acoustical cap of  FIG. 7A  where the acoustical cap is in a second orientation relative to the lavalier microphone; and 
         FIG. 9  is a diagram of a Helmholtz resonator. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of the various examples, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration various examples in which aspects may be practiced. References to “embodiment,” “example,” and the like indicate that the embodiment(s) or example(s) of the invention so described may include particular features, structures, or characteristics, but not every embodiment or example necessarily includes the particular features, structures, or characteristics. Further, it is contemplated that certain embodiments or examples may have some, all, or none of the features described for other examples. And it is to be understood that other embodiments and examples may be utilized and structural and functional modifications may be made without departing from the scope of the present disclosure. 
     Unless otherwise specified, the use of the serial adjectives, such as, “first,” “second,” “third,” and the like that are used to describe components, are used only to indicate different components, which can be similar components. But the use of such serial adjectives are not intended to imply that the components must be provided in given order, either temporally, spatially, in ranking, or in any other way. 
     Also, while the terms “front,” “back,” “side,” and the like may be used in this specification to describe various example features and elements, these terms are used herein as a matter of convenience, for example, based on the example orientations shown in the figures and/or the orientations in typical use. Nothing in this specification should be construed as requiring a specific three dimensional or spatial orientation of structures in order to fall within the scope of the claims. 
     Lavalier microphones may be used with an acoustical cap that covers the microphone and creates a resonant cavity. The microphone can be any number of different types, including MEMS, condenser, dynamic, ribbon, and optical. 
     The acoustical cap has inlets that allow sound to enter a resonant cavity. By adjust the sizes and shape of inlet and resonant cavity created by the acoustical cap, one can adjust the frequency response of sound that the microphone receives. For example, one can design the acoustical cap&#39;s inlet and respective resonant cavity to form a Helmholtz resonator. The classic Helmholtz resonator is a tube connected to a volume of air as shown in  FIG. 9 . 
       FIG. 9 , D is the tube diameter, and L is the tube length. V is the volume of air in the acoustical cavity in which the resonator terminates. Using these basic measurements, one can use the following equations as first order approximations to design the resonant cavity for specific performance characteristics: 
     
       
         
           
             M 
             = 
             
               
                 Acoustical 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 Moving 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 Mass 
               
               = 
               
                 
                   
                     
                       ρ 
                       0 
                     
                     ⁢ 
                     L 
                   
                   
                     π 
                     ⁢ 
                     
                       r 
                       2 
                     
                   
                 
                 ⁢ 
                 
                   
                     k 
                     ⁢ 
                     g 
                   
                   
                     m 
                     3 
                   
                 
               
             
           
         
       
       
         
           
             
               C 
               v 
             
             = 
             
               
                 Acoustical 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 Compliance 
               
               = 
               
                 
                   V 
                   
                     
                       ρ 
                       0 
                     
                     ⁢ 
                     
                       c 
                       2 
                     
                   
                 
                 ⁢ 
                 
                   
                     m 
                     5 
                   
                   N 
                 
               
             
           
         
       
       
         
           
             R 
             = 
             
               
                 Acoustical 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 Resistance 
               
               = 
               
                 
                   
                     
                       √ 
                       2 
                     
                     ⁢ 
                     ω 
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                       ρ 
                       0 
                     
                     ⁢ 
                     μ 
                   
                   
                     π 
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                 ⁢ 
                 
                   ( 
                   
                     
                       L 
                       r 
                     
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                     2 
                   
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                     N 
                     * 
                     s 
                   
                   
                     m 
                     5 
                   
                 
               
             
           
         
       
       
         
           
             
               f 
               0 
             
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                 Resonant 
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                 Frequency 
               
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                   1 
                   
                     2 
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                     π 
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                         M 
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                           C 
                           v 
                         
                       
                     
                   
                 
                 ⁢ 
                 Hz 
               
             
           
         
       
       
         
           
             Q 
             = 
             
               
                 Quality 
                 ⁢ 
                 
                     
                 
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                 Factor 
               
               = 
               
                 
                   1 
                   R 
                 
                 ⁢ 
                 
                   
                     M 
                     
                       C 
                       v 
                     
                   
                 
               
             
           
         
       
       
         
           
             
               ρ 
               0 
             
             = 
             
               Density 
               ⁢ 
               
                   
               
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               of 
               ⁢ 
               
                   
               
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               Air 
             
           
         
       
       
         
           
             μ 
             = 
             
               Viscosity 
               ⁢ 
               
                   
               
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               Coefficient 
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               Air 
             
           
         
       
       
         
           
             c 
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               Speed 
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               Sound 
             
           
         
       
       
         
           
             r 
             = 
             
               Tube 
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               Radius 
             
           
         
       
       
         
           
             V 
             = 
             
               Cavity 
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               Volume 
             
           
         
       
       
         
           
             ω 
             = 
             
               Angular 
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               Frequency 
             
           
         
       
     
     The above equations represent a starting point for designing the shape of a resonant cavity between the acoustical cap and the microphone and would not be the sole predictor of performance. 
     Lavalier microphones may be wired or wireless. If wired, these microphones can be connected to a transmitter or receiver via any one of a variety of different cables, including a twisted wire pair, a coaxial cable, or fiber optics. These wired microphones can also connect to a transmitter or receiver using any one of a variety of different connectors, including a LEMO connector, an XLR connector, a TQG connector, a TRS connector, a USB, or RCA connectors. Lavalier microphones can also be wireless and connect an audio system through any one of a variety of protocols, including WiMAX, LTE, Bluetooth, Bluetooth Broadcast, GSM, 3G, 4G, 5G, Zigbee, 60 GHz Wi-Fi, Wi-Fi (e.g., compatible with IEEE 802.11a/b/g), or NFC protocols. In this embodiment, a transmitter can be included within or attached to the microphone. 
       FIG. 1  is a schematic of an example lavalier microphone. A MEMS microphone die  101  is attached to substrate  103 . Substrate  103  may be a printed circuit board (PCB). In this example, a MEMs microphone is used, but other types of microphones may be used. Further, the MEMs microphone die  101  may be attached to the substrate  103  with a die bonding material, such as an epoxy resin adhesive or silicone resin adhesive, so that no gap exists between the MEMs microphone die  101  and substrate  103 . 
     An ASIC (Application Specific Integrated Circuit) chip  105  is also connected to substrate  103 . The ASIC chip  105  is an integrated chip that amplifies the electrical output from MEMs microphone die  101 . It can also be mounted to substrate  103  by a die-bonding material, such as an epoxy resin adhesive or silicone resin adhesive, so that no gap exists between the ASIC chip  105  and substrate  103 . MEMs microphone die  101  and ASIC chip  105  can be connected electronically, such as by a wire, or can be incorporated into a single chip. 
     The described circuitry is surrounded in a mechanical enclosure  107 , which in certain examples can be in the form of a housing. Although illustrated as solid, the mechanical enclosure  107  can also be a hollow shell that is metal, rigid plastic, or similar material. In this embodiment, the substrate  103  would by placed inside the mechanical enclosure  107  and secured, for example, by using a friction fit to snap into the mechanical enclosure  107 , by an adhesive, by screws, or by some other similar means. 
     As illustrated in  FIG. 1 , sound reaches the MEMs microphone die  101  through sound passage  109 , which is defined by a hole in the substrate  103 , seal  111 , and acoustical mesh  113 . Seal  111  can be part of mechanical enclosure  107  or made of plastic, rubber, or other appropriate material to ensure that sound is confined to the sound passage  109 . Acoustical mesh  113  can be made of cloth (e.g., nylon) or metal (e.g., stainless steel) and protects the MEMs microphone die  101  from dust and moisture. 
     The configuration of the circuitry in  FIG. 1  is a back-port configuration, meaning that sound passage  109  includes a hole in substrate  103 . However, in other example, the sound passage  109 —and consequently, seal  111  and wire mesh  113 —could be on the opposite side of the mechanical enclosure  107 . This is a front-port configuration. The hole in substrate  103  would be unnecessary in this configuration. In yet another example, sound passage  109 —and consequently, wire mesh  113 —may be made in another side of the mechanical enclosure  107 , which would require a bend in the passage, and consequently, seal  111 . This is a side-port configuration. In a side-port configuration, sound passage  109  may or may not include a hole in the substrate  103  as in a back-port configuration. 
       FIG. 2  is a schematic of the lavalier microphone of  FIG. 1  that also includes acoustical cap  201  in a first orientation. Acoustical cap  201  has two sound inlets. For clarity, these will be referred to as presence boost inlet  202  and speech boost inlet  204 . In this orientation, acoustical cap  201  is oriented to allow sound to enter through sound presence boost inlet  202 , pass through the presence boost sound cavity  206 , pass through the acoustical mesh  113 , and pass through the sound passage  109  to reach the MEMs microphone die  101 . While in this orientation, sound may enter the speech boost inlet  204  and speech boost cavity  208 , but the sound will be inhibited from reaching the MEMs microphone die  101  because the mechanical enclosure  107  creates a barrier. 
       FIG. 3  is an example of a frequency response graph of a lavalier microphone without an acoustical cap.  FIG. 4  is an example frequency response graph of the lavalier microphone when the acoustical cap  201  is in the first orientation as illustrated in  FIG. 2 . In the example of  FIG. 4 , the frequency response is balanced through a wide frequency range with a “boost” at approximately 10 kHz with a quality factor of approximately 5, which would be beneficial in musical performances when a microphone would be expected to amplify a wide range of frequencies and would also account for the space of the room of the performance. 
       FIG. 5  is a schematic of the lavalier microphone of  FIG. 1  that includes an acoustical cap  201  in a second orientation that is rotated 180 degrees from the orientation in  FIG. 2 . In this orientation, acoustical cap  201  is oriented to allow sound to enter through speech boost inlet  204 , pass through speech boost cavity  208 , pass through the acoustical mesh  113 , and pass through the sound passage  109  to reach the MEMs microphone die  101 . While in this orientation, sound may still enter presence boost inlet  202  and sound presence boost cavity  206 , but the sound will be inhibited from reaching the MEMs microphone die  101  because the mechanical enclosure  107  creates a barrier. 
       FIG. 6  is an example frequency response graph of the lavalier microphone when the acoustical cap  201  is in the second orientation as illustrated in  FIG. 6 . In this example, the frequency response includes a mid-frequency “boost” at approximately 6 kHz with a quality factor of approximately 8, which would emphasize speech. This frequency response would be helpful when the lavalier microphone is used in a film or news reporting situations and when the microphone is buried in clothing to hide the microphone from view. 
       FIGS. 7A, 7B, 8A, and 8B  are illustrations of a lavalier microphone with an acoustical cap.  FIGS. 7A and 7B  are illustrations of the lavalier microphone with the acoustical cap in a specific orientation, while  FIGS. 8A and 8B  are the same lavalier microphone with the same acoustical cap but rotated 180 degrees in relation to the lavalier microphone from the orientation of  7 A and  7 B. 
     Specifically,  FIG. 7A  is an illustration of a lavalier microphone with an acoustical cap  701  in a first orientation relative to the microphone.  FIG. 7A  shows an angled top perspective with an inlet  703  visible on the top of acoustical cap  701 . Inlet  703  allows for sound to pass through to a resonant cavity between the acoustical cap  701  and the microphone.  FIG. 7B  is a cross section of this example, showing the acoustical cap  701  and mechanical enclosure  705  of the lavalier microphone. As stated, in this orientation, sound will pass through inlet  703  to sound cavity  707 , which produces a specific frequency response based on the shape of inlet  703  and sound cavity  707 . The sound would then enter the microphone through sound passage  709  in mechanical enclosure  705  for processing.  FIG. 7B  also shows a second inlet  711  for sound to enter into a second sound cavity  713 . Although sound may enter inlet  711  into sound cavity  713 , the sound is prevented from entering sound cavity  707 , and thus sound passage  709 , because it is blocked by mechanical enclosure  705 &#39;s contact with acoustical cap  701 , as illustrated. 
       FIG. 8A  is an illustration of the lavalier microphone from  FIGS. 7A and 7B  but with acoustical cap  701  in a second orientation relative to the lavalier microphone.  FIG. 8A  shows a side view of acoustical cap  701  with inlet  711  visible.  FIG. 8B  is a cross section of this example showing acoustical cap  701  rotated 180 degrees in relation to mechanical enclosure  705 . In this orientation, sound will pass through inlet  711  to sound cavity  713 , which produces a specific sound frequency response based on the shape of inlet  711  and sound cavity  713  that is different from the frequency response produced by sound inlet  703  and sound cavity  707 . Sound would then enter the microphone as before through sound passage  709  of mechanical enclosure  705  for processing. Sound may still enter inlet  703  and sound cavity  707 , but the sound is prevented from entering sound cavity  713 , and thus sound passage  709 , because it is again blocked by mechanical enclosure  705 &#39;s contact with acoustical cap  701  as illustrated. 
     The inlet and sound cavity combinations of the above embodiments are just examples of possible resonators, and it is understood that various sizes and shapes of both inlets and cavities may be used. Thus, one can use this technology in a variety of settings (e.g., theater, small venue, concert hall, auditorium) and for a variety of purposes (e.g., miking instruments or voices, miking for a musical performance or public speaking event) by creating various frequency responses for the microphone. 
     In the example illustrated in  FIGS. 7 and 8 , both the acoustical cap  701  and mechanical enclosure  705  are depicted as cylinders, but both could also be a variety of shapes (e.g., cubes, rectangular prisms, spheres). Further, the acoustical cap can have more than two inlets and corresponding cavities. For example, a cylindrical acoustical cap could include a four different inlets and corresponding cavities separated by 90 degrees around the cylinder. The placement of the inlets and corresponding cavities on the acoustical cap can be based on the size and shape of the both the mechanical enclosure and acoustical cap and the location of the sound passage (e.g., whether it is in a front, back, or side port configuration). 
     In the example of  FIGS. 7-8 , acoustical cap  701  is attached to mechanical enclosure  705  by sliding the acoustical cap  701  over the mechanical enclosure  705 . Although not pictured, the acoustical cap  701  could be secured to the mechanical enclosure  705  in a variety of methods, including a snap-fit type connection (e.g., projections on mechanical enclosure  705  that engage with cutouts on acoustical cap  701 ), latches, buttons, or straps. These type of connections would allow a user to completely remove acoustical cap  701  from the mechanical enclosure  705 , such as when a user is removing acoustical cap  701  to turn the cap to utilize another sound inlet and corresponding cavity or when a user is substituting the cap for another. 
     Alternatively, an acoustical cap could be fixed to the mechanical enclosure. In this example, the acoustical cap would be attached in a way that it could swivel or rotate around the mechanical enclosure (e.g., by a screw or pin) so a user would alternate between various inlets and cavities by swiveling or rotating the acoustical cap around the mechanical enclosure. 
     In another example, a microphone unit comprises a microphone assembly, a mechanical enclosure that houses the microphone assembly. The mechanical enclosure comprises an outer surface, a sound inlet on the outer surface, and a sound passage that allows sound to travel from the sound inlet to a microphone. The mechanical enclosure may further include a seal that surrounds the sound pathway. The microphone unit also comprises an acoustical cap with an outer surface and an inner surface defining a cavity within which the mechanical enclosure may be coupled. The acoustical cap comprises at least two acoustical inlets in the outer surface and at least two resonant cavities that have openings on the inner surface in the acoustical cap, wherein at least a first acoustical inlet of the at least two acoustical inlets connects to a first resonant cavity of the at least two resonant cavities, and at least a second acoustical inlet of the at least two acoustical inlets connects to a second resonant cavity of the at least two resonant cavities. The first acoustical inlet differs in dimensions than the second acoustical inlet. Further, the first resonant cavity differs in dimensions than the second resonant cavity. The two different resonator cavities cause at least two different frequency responses. For instance, one frequency response could emphasize frequencies associated with a human voice or to emphasize a specific frequency such as 10 kHz. The acoustical cap is removably coupled to the mechanical enclosure. The microphone assembly may further comprise a transmitter to allow the microphone unit to wirelessly connect to a receiver. 
     The above examples provide acoustical caps having more than one acoustical response. In certain examples having separate acoustical caps for different recording situations may require a user to carry multiple acoustical caps. If a user only has a single acoustical cap, that acoustical cap may not allow the user to adjust on the fly the frequency response of the sound that the microphone receives. Further, having acoustical caps with only a single frequency resonator may require manufacturers to produce and sell many different acoustical caps for the various circumstances one would utilize these type of microphones. This may add inefficiencies in the manufacturing process and supply chain. 
     Finally, although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.