microphone

Abstract

The present application relates to a microphone, comprising: a microphone body; a first transducer assembly disposed in the microphone body and defining an internal acoustic volume, the first transducer assembly comprising a diaphragm having at least one pore passing through the diaphragm; and an external acoustic volume located outside the first transducer assembly, the external acoustic volume being in acoustic communication with the internal acoustic volume, wherein an external acoustic delay associated with the at least one pore is substantially equal to zero.

Description

[0001] Information about divisional applications

[0002] This case is a divisional application. The parent case of the divisional application is an invention patent application with application date of July 18, 2018, application number 201880054693.9, and invention name “Mobile coil microphone transducer with auxiliary port”.

[0003] Cross Reference

[0004] This application claims the benefit of U.S. Patent Application No. 15 / 653,217, filed on July 18, 2017, the entire contents of which are incorporated herein. Technical Field

[0005] The present application relates generally to a dynamic microphone. In particular, the present application relates to minimizing the internal acoustic volume of a moving coil microphone transducer. Background Art

[0006] There are several types of microphones and related transducers (e.g., dynamic, crystal, condenser / capacitor (external bias and electret), etc.), which can be designed with various polar response patterns (cardioid, supercardioid, omnidirectional, etc.) Each type of microphone has its advantages and disadvantages depending on the application.

[0007] One advantage of dynamic microphones (including moving coil microphones) is that they are passive devices and therefore do not require active circuitry, external power supplies, or batteries to operate. In addition, dynamic microphones are generally robust or rugged, relatively inexpensive and less susceptible to moisture / humidity issues, and they exhibit potentially high gain before causing audio feedback issues. These attributes make dynamic microphones ideal for stage use and better suited to handling high sound pressures such as, for example, from close vocal programs, certain instruments (e.g., kick drums and other percussion instruments), and amplifiers (e.g., guitar amplifiers).

[0008] However, dynamic microphone capsules are typically larger than, for example, condenser microphones. This is because dynamic microphones typically employ acoustical compliance, or a large internal cavity C1 behind the diaphragm. A larger cavity tends to increase the overall axial length of the dynamic transducer, which increases the overall capsule size and limits the usable form factor and practical applications of the microphone.

[0009] Therefore, there is a need for a dynamic microphone transducer that provides, among other things, an improved form factor without sacrificing professional grade dynamic microphone performance. Summary of the invention

[0010] The present invention seeks to solve the above and other problems by, among other things, providing a moving coil microphone transducer having an active diaphragm port and an auxiliary port configured to be positioned parallel to the active diaphragm port and to introduce zero acoustic delay relative to the active diaphragm port. This arrangement effectively uses external acoustic volume to satisfy internal acoustic compliance requirements, thereby allowing the internal cavity volume of the transducer to be minimized.

[0011] For example, one embodiment includes a microphone transducer comprising a housing and a transducer assembly supported within the housing and defining an internal acoustic space. The transducer assembly includes: a magnet assembly; a diaphragm disposed adjacent to the magnet assembly and having a front surface and a rear surface; and a coil attached to the rear surface of the diaphragm and capable of moving relative to the magnet assembly in response to sound waves impinging on the front surface. The transducer assembly further includes: a primary port establishing acoustic communication between the internal acoustic space and an external cavity at least partially within the housing; and an auxiliary port positioned at the front surface of the diaphragm.

[0012] Another example embodiment includes a moving coil transducer assembly for a microphone. The transducer assembly includes a magnet assembly and a diaphragm disposed adjacent to the magnet assembly, the diaphragm having a front surface and a rear surface. The transducer assembly further includes a coil attached to the rear surface and capable of interacting with a magnetic field of the magnet assembly in response to sound waves impinging on the front surface. The transducer assembly also includes a first acoustic path adjacent to the rear surface of the diaphragm, and a second acoustic path through the front surface of the diaphragm.

[0013] Another example embodiment includes a microphone comprising a microphone body and a transducer assembly disposed in the microphone body and defining an internal acoustic volume. The transducer assembly includes a diaphragm having at least one aperture disposed through a front surface of the diaphragm. The microphone further includes an external acoustic volume positioned outside the transducer assembly, the external acoustic volume being in acoustic communication with the internal acoustic volume.

[0014] These and other embodiments, as well as various permutations and aspects, will be apparent and more fully understood from the following detailed description and accompanying drawings, which set forth illustrative embodiments that are indicative of the various ways in which the principles of the invention may be employed. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1is a schematic diagram illustrating the general appearance of a conventional moving coil microphone transducer assembly.

[0016] Figure 2 is a schematic diagram illustrating the general topography of an example moving coil microphone transducer assembly in accordance with one or more embodiments.

[0017] Figure 3 is a front cross-sectional view of an example moving coil microphone transducer in accordance with one or more embodiments.

[0018] Figure 4 yes Figure 3 A perspective cross-sectional view of the moving coil microphone transducer depicted in FIG.

[0019] Figure 5 is disposed in a portion of a microphone body according to one or more embodiments Figure 3 and 4 A perspective cross-sectional view of the moving coil microphone transducer depicted in FIG.

[0020] Figure 6 is a perspective view of an example diaphragm according to one or more embodiments.

[0021] Figure 7 is a front cross-sectional view of another example moving coil microphone transducer in accordance with one or more embodiments. DETAILED DESCRIPTION

[0022] The following description describes, illustrates and exemplifies one or more specific embodiments of the present invention according to the principles of the present invention. This description is not provided to limit the present invention to the embodiments described herein, but is used to illustrate and teach the principles of the present invention so that those skilled in the art can understand these principles, and with the understanding, can apply the principles to practice not only the embodiments described herein but also other embodiments that can be thought of according to these principles. The scope of the present invention is intended to cover all such embodiments that fall within the scope of the appended claims either literally or under the doctrine of equivalents.

[0023] It should be noted that in the description and drawings, the same or substantially similar elements may be marked by the same element symbols. However, sometimes these elements may be marked by different numbers, for example, such as in cases where such marking facilitates a clearer description. In addition, the drawings set forth herein are not necessarily drawn to scale, and in some examples, the scale may have been enlarged to more clearly depict certain features. Such marking and drawing practices do not necessarily involve potential general purposes. As stated above, this specification is intended to be viewed as a whole and interpreted according to the principles of the present invention as taught herein and as understood by those skilled in the art.

[0024] Figure 1The topography of a typical or conventional moving coil microphone transducer 10 is illustrated, which is shown with reference to a device designed according to the techniques described herein and in Figure 2 The morphology of the moving coil microphone transducer 20 shown in FIG. Figure 1 , a conventional transducer 10 has an acoustic compliance C1 defined behind a diaphragm 12 and in the form of a cavity 14 having a length l1. The external acoustic delay d1 of the transducer is defined by the distance (represented by resistance R1) between the front surface of the diaphragm 12 and a primary tuning port 16 located behind or at the rear of the diaphragm 12. Port 16 (also referred to as an "active diaphragm port" or "rear port") establishes acoustic communication between the internal cavity volume C1 and the external volume of a housing 18 surrounding the transducer 10. Figure 1 The acoustic flow (or path) for capturing sound waves from the rear of the transducer 10 is illustrated by the dashed line 19 which enters the acoustic cavity 14 via the primary port 16 .

[0025] The value of the cavity compliance C1, or the size of the internal cavity 14, depends on the primary port resistance R1 (also called "diaphragm tuning resistance" or "back port resistance") and the external acoustic delay d1. Since a typical directional moving coil transducer has a relatively large diaphragm, the distance across the front surface of the diaphragm is also large, resulting in a large external acoustic delay d1. The large external acoustic delay d1 is offset by a corresponding internal acoustic delay, which is designed to produce a phase shift to eliminate sound waves approaching from the direction that defines the external delay d1. The internal acoustic delay is produced by the diaphragm tuning resistance R1 working in conjunction with the internal cavity volume of the transducer. In particular, the internal acoustic delay can be made larger by setting the internal cavity volume or cavity compliance C1 to a high value and setting the tuning resistance R1 to a low value. The diaphragm tuning resistance R1 is set to a low value due to the following two characteristics of the transducer. First, assuming that the diaphragm tuning resistance R1 is connected to the diaphragm volume velocity, the resistance R1 is usually set equal to the critical damping resistance R of the diaphragm / coil system. d The value of R must be set to strictly suppress the diaphragm movement. d Set to a very low value to allow the moving coil microphone transducer to reproduce the entire audio bandwidth (eg, 20 Hertz (Hz) ≤ f ≤ 20 Kilohertz (kHz)).

[0026] Therefore, in a conventional moving coil microphone transducer, to improve the bandwidth of the transducer (e.g., to lower the lower cutoff frequency), the diaphragm tuning resistance R1 must be reduced to R d Therefore, the internal cavity volume of the typical directional moving coil microphone transducer 10 is relatively large, which tends to increase the overall axial length l1 of the transducer 10, such as Figure 1This configuration limits the usable form factor and applications of conventional moving coil microphone transducers.

[0027] In contrast, Figure 2 A moving coil microphone transducer 20 (also referred to herein as a "transducer assembly") according to an embodiment is shown, which includes, in addition to Figure 1 In addition to the diaphragm 12 and rear port 16 shown in FIG. 1 , an auxiliary tuning port 22 is also included, which is located at the front surface of the diaphragm 12. f The auxiliary port 22 shown is generally parallel to the central axis of the transducer assembly 20 (or the diaphragm 12 contained therein), and it introduces or provides a second acoustic flow (or path) through the front of the diaphragm 12 and along the central axis, as shown in FIG. Figure 2 2 is shown by the second dashed line 24. In addition, the auxiliary port 22 is positioned substantially parallel to the primary port 16. Thus, ports 22 and 16 form two parallel acoustic branches or paths in the transducer 20 (i.e., one path through each port), and the total series resistance as experienced by the diaphragm 12 of the transducer 20 is equal to R1║R f or the parallel equivalent resistance across the two acoustic branches (i.e., R f *R1 / (R f +R1)).

[0028] In an embodiment, the total series resistance of the transducer 20 is set equal to the critical damping resistance R of the diaphragm / coil system. d (i.e., R d =R1║R f ) to strictly inhibit diaphragm movement, just like Figure 1 However, assuming that the directivity condition is not affected by the resistance R f The value of the diaphragm tuning resistance R1 in the transducer 20 can be affected by the critical damping resistance R d decoupled (eg, need not be equal), which is different from transducer 10. For example, as long as equation R d =R1║R f , then the transducer 20 will still meet the internal acoustic compliance requirement even if R1 is increased to exceed R d Therefore, by choosing the parallel port resistance R f The resistance R1 can be increased to a value greater than the low critical damping resistance R d The value of .

[0029] In an embodiment, the diaphragm tuning resistance R1 of transducer 20 is increased to a high value, which allows for a reduction in cavity compliance C2 or a smaller sized internal cavity 26 due to the inverse relationship between diaphragm tuning resistance and internal cavity volume described above. Figure 2As shown in FIG. 1 , a smaller internal acoustic volume C2 can be obtained by selecting a smaller length l2 (e.g., Figure 1 In this way, adding the port 22 can minimize the internal cavity 26, thereby reducing the overall external size of the microphone transducer 20. In addition, the presence of the auxiliary port 22 can help to lower the cutoff frequency of the microphone transducer 20 because the diaphragm tuning resistance R1 does not need to be reduced to the critical damping resistance R d level.

[0030] In an embodiment, to prevent the reduced cavity compliance C2 from affecting the bandwidth and directivity (e.g., polar pattern) of the transducer 20, the microphone transducer 20 is configured such that the external acoustic delay d1 remains unchanged. This can be achieved by selecting a position of the auxiliary port 22 relative to the diaphragm 12 that does not introduce additional acoustic external delay (i.e., other than d1). For example, in Figure 2 , the auxiliary port 22 or the parallel acoustic branch formed thereby is co-located with or passes through the center of the front surface of the diaphragm 12 (e.g., on the central axis of the diaphragm 12), so that the second external acoustic delay d2 defined by the distance between the front surface of the diaphragm 12 and the auxiliary port 22 is zero (i.e., d2=0). During operation, due to the position of the parallel acoustic path, the transducer 20 can effectively use the volume outside the housing 18 to meet the internal acoustic compliance requirements, even though the cavity 26 is smaller. That is, the transducer 20 uses the external acoustic volume in combination with the internal acoustic volume 26 to perform microphone operation.

[0031] Thus, the techniques described herein provide a moving coil microphone transducer 20 in which the diaphragm tuning resistance R1 and the internal cavity compliance C2 can be adjusted without affecting basic microphone operation (i.e., bandwidth and directivity requirements). In some cases, the internal cavity 26 is minimized so that the microphone capsule can have a lower profile and overall mass for high sound pressure level (SPL) applications (e.g., guitar amplifiers, percussion instruments, etc.). In other cases, the internal cavity volume C2 can be adjusted to obtain a desired polar pattern (e.g., unidirectional, omnidirectional, cardioid, etc.). In either case, adjustment of the cavity compliance C2 parameter can be at least partially achieved by adjusting the tuning inertia L1 and / or external delay d1 values ​​of the microphone transducer 20.

[0032] In an embodiment, adding the auxiliary port 22 to the microphone transducer 20 can reduce the lower cutoff frequency (e.g., f L=110 Hz) without increasing the internal cavity volume C2 to restore rejection and significantly improve the performance of conventional transducer designs. However, the acoustic sensitivity of the microphone transducer 20 (e.g., f=1 kHz) may be affected by the presence of the auxiliary port 22 and / or the reduced internal cavity volume C2. In particular, the microphone sensitivity may be reduced by a desired gain factor G, where G=R d / R1. In one example embodiment, the auxiliary port 22 causes a reduction in the mid-band frequency response while maintaining the low and high frequency responses. Despite the lower mid-band sensitivity, the overall output of the microphone transducer 20 may be more balanced and sufficient for certain applications. For example, the reduced sensitivity may not be a problem for high sound pressure level (SPL) applications (e.g., guitar amplifiers, percussion instruments, etc.) or close-range conditions (e.g., vocal programs, etc.) or when amplification can be used. In some cases, the lower microphone sensitivity may be compensated by external means (e.g., such as active amplification, optimized magnetic circuits, etc.).

[0033] In an embodiment, adding the auxiliary port 22 to the diaphragm 12 does not change the low impedance characteristics of the transducer 20, at least because the branch resistance R f and diaphragm resistance Z m Therefore, the total equivalent impedance experienced by the diaphragm 12 is equal to R f ║Z m (i.e., R f *Z m / (R f +Z m )), which remains low because the equation is derived from the parallel branch resistance R f As mentioned above, you can choose the parallel branch resistance R f The diaphragm tuning resistance R1 can be increased to be higher than the critical damping resistance R d , while still keeping the total series resistance of the transducer 20 equal to or below the critical damping resistance R d (i.e., R d =R1║R f ). In some embodiments, the parallel branch resistance R f Selected to be greater than the critical damping resistance R d (i.e., produces an over-damping effect), so that adding the auxiliary port 22 to the diaphragm 12 effectively simplifies the acoustic design of the unidirectional moving coil microphone transducer to the acoustic design of a unidirectional capacitive transducer. f Selected to be less than the critical damping resistance R d , for example, in microphone applications where an underdamped effect is desired (e.g., in the case of a kick drum microphone). In other embodiments, the parallel branch resistance R f is chosen to be equal to the critical damping resistance Rd To produce an isolated transducer for active vibration cancellation (eg, using an accelerometer) that inherently matches a non-isolated active transducer.

[0034] Reference Figures 3 to 5 , which shows a cross-sectional view of an example moving coil microphone transducer 30 according to a particular embodiment. As illustrated, the transducer 30 includes a housing 32 and a transducer assembly 40 supported within the housing 32 to receive sound waves. Figure 3 and 4 , portions of the microphone transducer 30, including the housing 32 and the diaphragm 42, are shown as transparent for illustrative purposes. In embodiments, the housing 32 may form all or part of a microphone capsule that encloses the microphone transducer 30 and is connected to a larger microphone body 34 that is located at the bottom of the microphone body. Figure 5 Also in the embodiment, the transducer assembly 40 is at least similar in appearance to Figure 2 30 and has the same or similar functions and advantages as the microphone transducer 20 described above. In a particular embodiment, the microphone transducer 30 is configured for unidirectional microphone operation. In other embodiments, the microphone transducer 30 may be configured for other operating modes (cardioid, omnidirectional, etc.).

[0035] The transducer assembly 40 includes a magnet assembly 41 and a diaphragm 42 disposed adjacent to the magnet assembly 41. The diaphragm 42 has a front surface 43 disposed adjacent to the front inner surface of the housing 32 and an opposite rear surface 44 disposed adjacent to the magnet assembly 41. The front surface 43 of the diaphragm 42 is configured to allow sound waves to impinge thereon. The rear surface 44 of the diaphragm 42 is connected or attached to a coil 45 at an attachment point 46. As shown, the coil 45 is suspended from the diaphragm attachment point 46 and extends into the magnet assembly 41 without touching the side of the magnet assembly 41. The coil 45 is located within the transducer assembly 40 in this manner to be able to interact with the magnetic field of the magnet assembly 41 in response to sound waves impinging on the front surface 43 of the diaphragm 42.

[0036] The transducer assembly 40 defines an internal acoustic space 47 and includes at least one air passage or port 48 to establish or facilitate acoustic communication between the internal acoustic space 47 and an external cavity 50 positioned outside the transducer assembly 40. As shown, the external cavity 50 includes an acoustic space or volume defined between the housing 32 and the transducer assembly 40. The external cavity 50 may also include an acoustic space or space surrounding the microphone transducer 30 positioned outside the housing 32. As shown, the acoustic port 48 is formed below the outer edge portion 51 of the diaphragm 42 or adjacent to the rear surface 44 of the diaphragm 42. The outer edge of the diaphragm rim 51 is attached to the top of the magnet assembly 41 and / or the housing 32, while the inner edge of the diaphragm rim 51 is attached to the coil 45, thus creating a volume below the rim portion 51 of the diaphragm 42. In embodiments, the acoustic port 48 (also referred to herein as a "primary tuning port") may form all or part of a phase delay network for tuning the directivity of the microphone transducer 30. In the embodiment shown, two ports 48 are implemented on both sides of the transducer assembly 40. In other embodiments, the transducer assembly 40 may include a single port 48 on only one side of the transducer assembly 40.

[0037] The magnet assembly 41 includes a centrally disposed magnet 52 having its magnetic poles arranged substantially vertically along a central vertical axis of the housing 32. The magnet assembly 41 also includes an annular bottom pole piece 54, which is concentrically located outward from the magnet 52 and has the same magnetic pole as the magnetic pole of the upper portion of the magnet 52. The magnet assembly 41 further includes a top pole piece 56, which is disposed above the central magnet 52 and adjacent to the upper arm of the bottom pole piece 54. The top pole piece 56 has a magnetic pole opposite to the magnetic pole of the upper portion of the central magnet 52. When an acoustic wave impinges on the front diaphragm 42, the coil 45 moves relative to the magnet assembly 41 and its associated magnetic field to generate an electrical signal corresponding to the acoustic wave. The electrical signal can be transmitted via a coil connector and associated terminal leads (e.g., Figure 4 The electrical leads 60 shown in Figure 5 The electrical leads 61) shown in the figure are used for transmission.

[0038] The interior acoustic space 47 (e.g., similar to that described above and in Figure 2 The internal cavity 26 shown in FIG. 2 is defined by the space behind or adjacent to the rear surface 44 of the diaphragm 42, the central space generally associated with the magnet assembly 41, and the rear or back space located below the magnet assembly 41, such as Figures 3 to 5 The internal acoustic space 47 also includes a gap 57 formed around the coil 45, or a space between the coil 45 and the magnet 52 and a space between the coil 45 and the top pole piece 56. The main tuning port 48 (e.g., similar to that described above and in Figure 2) facilitates acoustic communication between the interior acoustic space 47 and the exterior cavity 50. In the illustrated embodiment, each primary port 48 is an aperture within the top pole piece 56 (also referred to herein as the "top") of the magnet assembly 41 to create an acoustic flow or path adjacent to the rear surface 44 of the diaphragm 42. The acoustic impedance 62 (e.g., similar to that described above and in Figure 2 The resistance R1 shown in FIG. 4 is disposed between the two pieces of the top pole piece 56 so that the sound waves passing through the port 48 encounter the acoustic resistance 62. The acoustic resistance 62 may be a fabric, a mesh, or other suitable material for creating a resistance to the acoustic flow at the port 48.

[0039] In an embodiment, the transducer assembly 40 further includes an auxiliary port 64 positioned at the front surface 43 of the diaphragm 42 to create an acoustic flow or path through the front surface 43. As shown, the auxiliary port 64 (e.g., similar to that described above and in Figure 2 The auxiliary port 64 is positioned generally parallel to the main port 48 positioned below or behind the outer edge 51 of the diaphragm 42. The auxiliary port 64 may be formed by or include one or more apertures disposed in or through the front surface 43 of the diaphragm 42, such as Figure 6 4 and described in more detail below. In the illustrated embodiment, the auxiliary port 64 is a single port positioned at the center and / or top of the dome 65 formed by the diaphragm 42, so that the acoustic delay between the main port 48 and the auxiliary port 64 is zero (e.g., d2=0). Placing the auxiliary port 64 at the center of the diaphragm 42 may provide the best or preferred frequency response performance of the microphone transducer 30. However, in other cases, if other frequency responses are preferred or can be tolerated, the auxiliary port 64 may be placed elsewhere on the diaphragm 42. For example, in such cases, the auxiliary port 64 may include multiple ports placed evenly across the diaphragm 42 or in a concentric array spread across the diaphragm 42.

[0040] Figure 6 An example auxiliary port 72 (e.g., similar to Figures 3 to 5 The auxiliary port 64 shown in FIG. Figures 3 to 5 The auxiliary port 72 is configured to create an acoustic impedance through the diaphragm 70 and substantially parallel to the acoustic impedance formed below the diaphragm 70 (e.g., similar to Figures 3 to 5 The second acoustic flow resistance (e.g., similar to the acoustic resistance 62 shown in FIG. Figure 2 The parallel port resistance R shown in f ).

[0041] In the illustrated embodiment, the auxiliary port 72 is located at the center of the dome portion 74 of the diaphragm 70 (e.g., similar to Figures 3 to 5 The dome portion 74 is formed by a resilient rim 76 (e.g., similar to Figures 3 to 5 In an embodiment, the diaphragm 70 is a one-piece structure such that the dome portion 74 and the resilient rim 76 are formed from a continuous piece of material. The outer edge 78 of the rim 76 can be attached to a transducer assembly including the diaphragm 70 (e.g., Figures 3 to 5 The top surface of the transducer assembly 40 shown in FIG. 1 is shown in FIG. 1 . The elastic rim 76 is connected or attached to the dome portion 74 at the inner edge 79. The rear surface of the inner edge 79 (e.g., similar to Figures 3 to 5 Attachment point 46 shown in FIG. 4) is attached to a coil of a transducer assembly (e.g., similar to Figures 3 to 5 In one embodiment, one or more acoustic paths are provided by a tuning port (e.g., similar to Figures 3 to 5 These acoustic paths are generally parallel to the acoustic paths formed by the auxiliary ports 72 through the diaphragm 42.

[0042] As shown, the auxiliary port 72 may be formed by a plurality of apertures 80. In some embodiments, the apertures 80 are patterned directly into or formed through the diaphragm material itself using, for example, laser cutting, die cutting, or other manufacturing techniques capable of perforating or creating holes in the diaphragm 70. In such cases, the patterned portion of the diaphragm 70 acts as a second acoustic resistance (e.g., R ) for any sound waves passing through the auxiliary port 72. f In other embodiments, the auxiliary port 72 is created by forming an aperture or hole 82 through the diaphragm 70 and covering the hole 82 with a separate sheet of material that includes a plurality of apertures 80 or is otherwise configured to provide a second acoustic impedance (e.g., R f ). In such cases, the diaphragm hole 82 may be formed by cutting or otherwise removing a portion of the diaphragm 70. The acoustically resistive material may be attached to the diaphragm material around the hole 82 using glue or other suitable adhesive. As an example, the acoustically resistive material may be a mesh or piece of fabric pre-perforated with a plurality of apertures 80. In such embodiments, the acoustically resistive material (also referred to herein as "perforated material") is a lightweight, low inertia material to avoid mass loading the diaphragm 70 due to the additional mass of the acoustically resistive material, or otherwise altering the operation of the microphone transducer.

[0043] In some alternative embodiments, a second microphone transducer assembly may be added to the microphone transducer 30 to cancel vibrations, or otherwise mitigate vibration sensitivity effects in the microphone transducer 30 due to the addition of the auxiliary port 64. For example, while the acoustic sensitivity of the microphone transducer 30 is scaled by a factor of the expected gain G, where G=R d / R1, but the vibration sensitivity of the microphone does not scale. This is because the structural excitation of the transducer is a "base excitation" caused by displacement of the microphone handle, direct contact with the microphone capsule, or other treatment of the microphone base. The resulting vibration response or microphone treatment noise depends on the total system damping (i.e., the parallel combination of the exposed ports 48 and 64 of the microphone transducer 30) which cannot be changed by adding the auxiliary port 64. Instead, the acoustic excitation occurs through or via the exposed ports 48 and 64 of the microphone transducer 30 and is therefore dependent on the damping through the individual acoustic network paths. Therefore, compared with a conventional transducer without an auxiliary port (e.g., Figure 1 The addition of the auxiliary port 64 may reduce the acoustic response of the microphone transducer 30 compared to the conventional microphone transducer 10). However, when the acoustic response of the microphone transducer 30 is scaled to be equal to the acoustic response of the conventional microphone transducer (e.g., by adjusting the microphone gain), the vibration response of the microphone transducer 30 may appear to be higher than the vibration response of the conventional transducer. For example, in an embodiment, the vibration sensitivity of the microphone transducer 30 with the auxiliary port 64 may be greater than that of a conventional microphone transducer with the same acoustic sensitivity. -1 times. Furthermore, a moving coil microphone transducer (like transducer 30) is already very susceptible to structural excitations due to the presence of coil 45. Therefore, microphone transducer 30 may require a vibration mitigation strategy to counteract the effects of adding auxiliary port 64.

[0044] Reference Figure 7 , which presents a vibration mitigation strategy that uses a secondary transducer to cancel the vibrations generated by the primary transducer. More specifically, Figure 7 An example microphone transducer 130 is depicted, which includes a first microphone transducer assembly 140 (also referred to as a "primary transducer") and a second microphone transducer assembly 240 (also referred to as a "canceling transducer"). The first microphone transducer assembly 140 may be substantially similar to that in Figures 3 to 51 and described above. For example, the first transducer 140 may include a magnet assembly 141, a diaphragm 142, and a coil 145 that are substantially similar to the magnet assembly 41, the diaphragm 42, and the coil 45 of the microphone transducer 30. The first transducer 140 may also include a primary acoustic port 148 similar to the primary port 48 of the microphone transducer 30, and an auxiliary acoustic port 164 that passes through a central dome portion 165 of the diaphragm 142 similar to the auxiliary port 64 of the microphone transducer 30.

[0045] To simplify frequency response matching and other microphone design considerations, the second transducer assembly 240 may be substantially identical to the first transducer assembly 140. For example, the second transducer assembly 240 may have the same structural frequency response as the first transducer 140 and may be oriented along the same excitation axis as the first transducer 140 but with opposite polarity than the first transducer 140. In some cases, the second transducer 240 may also have the same moving coil transducer construction as the first transducer 140. For example, the second transducer assembly 240 may include a magnet assembly 241, a diaphragm 142, and a coil 245 that are substantially similar to the magnet assembly 141, the diaphragm 142, and the coil 145 of the first microphone transducer assembly 140.

[0046] As shown, the two microphone transducers 140 and 240 may be incorporated into the same housing 132 so that the transducers 140 and 240 act together as a single microphone capsule with built-in vibration cancellation. To remove the vibration signal from the primary transducer 140, the output of the auxiliary transducer 240 must be electrically "subtracted" from the output of the primary transducer 140, with due consideration for the total microphone electrical output impedance. In an embodiment, this may be accomplished using one of two mechanical / acoustic implementations to construct a microphone using two transducers.

[0047] A first example implementation for placing two transducers in one microphone capsule involves completely isolating the internal acoustic field C2 of the first transducer 140 from the internal acoustic field C3 of the second transducer 240, so that the two transducers 140 and 240 are completely independent. This implementation may be optimal under certain directional constraints, but does not allow minimizing the size of the microphone capsule. Therefore, the first implementation may not be preferred when trying to achieve a small form factor.

[0048] Figure 7 A second example implementation is described in which the second microphone transducer assembly 240 is placed within the internal acoustic cavity 147 (or acoustic domain C2) of the first microphone transducer assembly 140. As shown, the second transducer assembly 240 requires at least C3 = C f +C b The sound range or volume of Cf is the volume in front of the diaphragm 242 and C b is the volume behind the diaphragm 242. In a second embodiment, the acoustic domain C3 of the second transducer 240 is shared with the acoustic domain C2 of the first transducer 140. Cavities C2 and C3 may be coupled through a port 290 having an acoustic impedance R3 so that the second transducer 240 may operate within the primary tuning volume C2 of the first transducer 140. In some embodiments, the cancellation transducer 240 may be completely packaged within the primary transducer 140 so that no additional space is required to accommodate the second transducer assembly 240. In such cases, the size and shape of the housing 132 may be substantially similar to the housing 32 of the microphone transducer 30.

[0049] In the illustrated configuration, the second transducer 240 is coupled to the structural perturbations and internal acoustic perturbations of the first transducer 140, but can be isolated from the external acoustic perturbations experienced by the first transducer 140. This is because the internal acoustic domain C2 of the primary transducer 140 is partially isolated from external acoustic perturbations due to the acoustic resistance R1 through the primary port 148 of the first transducer 140. At the same time, the cavity resistance within the expected bandwidth causes the acoustic pressure to vary uniformly within the cavity C2. Therefore, the cavity pressure fluctuations of C2 do not excite the diaphragm 242 of the cancellation transducer 240 (or if they do excite the diaphragm 242, they can be accounted for in the resulting frequency response using known techniques). In addition, if additional isolation is required, then cavity segmentation through acoustic resistance grafting can be used, but depending on the resistance through the zero delay port 164, the resistance R1 through the primary port 148 can be large enough for isolation.

[0050] In an embodiment, at least for the above Figure 2 For the same reasons discussed above, the total series resistance of the first transducer 140 can be set to be equal to or lower than the critical damping resistance R d (i.e., R d =R1║R f1 ), where R f1 is the acoustic impedance through the auxiliary port 164 of the first transducer 140. To provide a matching vibration frequency response, the second transducer 240 may be configured to have the same R as the primary transducer 140. d This can be achieved at least in part by using the techniques described above to create an auxiliary port 264 through the diaphragm 242 of the second transducer 240 similar to the auxiliary port 164 of the first transducer 140. For example, the auxiliary port 264 can be created by creating a plurality of holes in the center of the central dome portion 265 of the diaphragm 242 or by placing a separate mesh or cloth over the holes through the central dome portion 265 (see, e.g., Figure 6). In addition, the second transducer 240 can be configured so that the auxiliary port 164 represents the only acoustic path from the front of the diaphragm 242 to the rear of the diaphragm 242, thereby making the total series resistance of the second transducer 240 equal to the acoustic resistance R through the auxiliary port 264. f2 Therefore, by simply changing the resistance R f2 Set equal to the critical damping resistance R d (i.e., R f2 =R d ), the vibration response of the second transducer 240 can match the vibration response of the first transducer 140.

[0051] In an embodiment, the internal cavity 147 of the first transducer assembly 140 can be increased by increasing the resistance R through the auxiliary port 164 of the first transducer 140. f1 Make it exceed the critical damping resistance R d (i.e., R f1 >R d ) and passing through the resistance R of the auxiliary port 264 of the second transducer 240 f2 is set equal to the critical damping resistance (i.e., R f1 =R d ) while keeping the size to a minimum (e.g., as Figure 3 Thus, by using the existing internal cavity 147 of the first transducer 140 to operably house the second transducer 240, the illustrated implementation can provide vibration cancellation without sacrificing a smaller microphone capsule size of the microphone transducer 130.

[0052] In some embodiments, microphone transducer 130 may be configured to obtain first order directivity while also accounting for the pressure response from auxiliary transducer 240 within the combined electrical signal output by microphone transducer 130. Although second transducer 240 is provided by a resistance R through auxiliary port 264 f2 The secondary transducer 240 is effectively bypassed, but the secondary transducer 240 may output a low level pressure response which, unless taken into account, may affect the frequency response of the primary transducer 140, or at least produce a "noise floor" that acts as a minimum rejection level of the polar pattern of the microphone. One technique to address this problem is to modify the polar response of the primary transducer 140 to match the pressure response of the secondary transducer 240 by intentionally "mistuning" the polar response of the primary transducer 140 so that when the response signal is subtracted, the resulting output signal is the desired polar response. For example, to obtain a unidirectional microphone using dual transducers in a shared volume implementation, the individual responses of the primary transducer 140 may be pushed toward omnidirectional compared to the desired polar response, and the secondary transducer 240 may have a cavity pressure or C in the cavity in front of the diaphragm at low frequencies. fProportional pressure response. At higher frequencies, the acoustic response may not be affected by the second transducer 240 because the amplitude of the pressure response decreases.

[0053] Thus, the techniques described herein provide for minimizing the internal acoustic volume of a moving coil microphone transducer, without sacrificing low frequency bandwidth (eg, f=100 Hz) or affecting the directional characteristics of the microphone, compared to conventional moving coil microphone transducers.

[0054] The present invention is intended to illustrate how to design and use various embodiments according to the present technology, rather than to limit the true, expected and reasonable scope and spirit of the present invention. The foregoing description is not intended to be exhaustive or limited to the precise form disclosed. In view of the above teachings, modifications or changes are possible. The embodiments are selected and described to provide the best description of the principles of the described technology and its practical application, and to enable those skilled in the art to utilize the technology in various embodiments and to expect various modifications to be suitable for specific purposes. All such modifications and changes are within the scope of the embodiments determined by the attached claims that may be amended during the pendency of this patent application and all its equivalents interpreted according to the scope of its authorization fairly, legally and reasonably.

Claims

1. A microphone, comprising: Microphone body; a first microphone transducer assembly disposed in the microphone body, the first microphone transducer assembly comprising a first diaphragm and an interior cavity defining an interior acoustic volume; an external acoustic volume located external to the first microphone-transducer assembly, the external acoustic volume being in acoustic communication with the internal acoustic volume; and A second microphone transducer assembly is disposed within the interior acoustic volume of the first microphone transducer assembly, the second microphone transducer assembly including a second diaphragm having one or more apertures therethrough. 2 . The microphone of claim 1 , wherein the first microphone transducer assembly further comprises a tuning port for establishing acoustic communication between the external acoustic volume and the internal acoustic volume.

3. The microphone of claim 2, wherein an acoustic resistance associated with the tuning port is less than a critical damping resistance of the first diaphragm.

4. The microphone of claim 2, wherein a first acoustic path formed by the tuning port is disposed substantially parallel to a second acoustic path formed by the one or more apertures in the second diaphragm.

5. The microphone of claim 1, wherein the one or more apertures include a plurality of apertures formed through a material of the second diaphragm and configured to create a resistance to acoustic flow through a center of the second diaphragm.

6. The microphone of claim 1, further comprising a perforated material configured to cover the one or more apertures and create a resistance to acoustic flow through a center of the second diaphragm.

7. A microphone, comprising: a microphone transducer assembly defining an internal acoustic volume and comprising a diaphragm and at least one aperture through the diaphragm; an external acoustic volume located external to the microphone transducer assembly; and a primary tuning port for establishing acoustic communication between the outer acoustic volume and the inner acoustic volume, Wherein an external acoustic delay between the primary tuning port and the at least one aperture is substantially equal to zero.

8. The microphone of claim 7, wherein an acoustic resistance associated with the primary tuning port is greater than a critical damping resistance of the diaphragm.

9. The microphone of claim 7, wherein the at least one aperture is disposed through a center of the diaphragm.

10. The microphone of claim 9, wherein the at least one aperture is covered by a perforated material configured to create a resistance to acoustic flow through the center of the diaphragm.

11. The microphone of claim 9, wherein the at least one aperture comprises a plurality of apertures configured to create a resistance to acoustic flow through the center of the diaphragm.

12. The microphone of claim 7, wherein a first acoustic path formed by the primary tuning port and a second acoustic path formed by the at least one aperture are disposed substantially parallel to a central axis of the diaphragm.

13. The microphone of claim 7, wherein the primary tuning port is located below a resilient rim of the diaphragm.

14. The microphone of claim 7, wherein the microphone transducer assembly further comprises: A magnet assembly disposed adjacent to the diaphragm and a coil attached to the rear surface of the diaphragm, the coil movable relative to the magnet assembly in response to sound waves impinging on the front surface of the diaphragm.

15. The microphone of claim 14, wherein the primary tuning port is an aperture within a top portion of the magnet assembly disposed adjacent to the rear surface of the diaphragm.

16. The microphone of claim 7, further comprising a second microphone transducer assembly in acoustic communication with the microphone transducer assembly.

17. The microphone of claim 7, further comprising a second microphone transducer assembly, wherein the microphone transducer assembly is disposed within an interior acoustic volume of the second microphone transducer assembly.

18. A microphone, comprising: Microphone body; a first microphone transducer assembly disposed in the microphone body and defining an internal acoustic volume, the first microphone transducer assembly comprising a diaphragm having at least one aperture therethrough; and an external acoustic volume located external to the first microphone transducer assembly, the external acoustic volume being in acoustic communication with the internal acoustic volume via a primary tuning port, Wherein an external acoustic delay between the primary tuning port and the at least one aperture is substantially equal to zero.

19. The microphone of claim 18, wherein the first microphone transducer assembly further comprises the primary tuning port for establishing acoustic communication between the external acoustic volume and the internal acoustic volume.

20. The microphone of claim 19, wherein an acoustic resistance associated with the primary tuning port is greater than a critical damping resistance of the diaphragm.

21. The microphone of claim 19, wherein a first acoustic path formed by the primary tuning port and a second acoustic path formed by the at least one aperture are disposed substantially parallel to a central axis of the diaphragm.

22. The microphone of claim 18, wherein the at least one aperture is disposed through a center of the diaphragm.

23. The microphone of claim 22, wherein the at least one aperture comprises a plurality of apertures configured to create a resistance to acoustic flow through the center of the diaphragm.

24. The microphone of claim 22, wherein the at least one aperture is covered by a perforated material configured to create a resistance to acoustic flow through the center of the diaphragm.

25. The microphone of claim 18, further comprising a second microphone transducer assembly disposed within the interior acoustic volume of the first microphone transducer assembly.

26. The microphone of claim 25, wherein the second microphone transducer assembly includes a second diaphragm having one or more second apertures therethrough.

27. The microphone of claim 18, further comprising a second microphone transducer assembly in acoustic communication with the first microphone transducer assembly.

28. The microphone of claim 18, further comprising a second microphone transducer assembly, wherein the first microphone transducer assembly is disposed within an interior acoustic volume of the second microphone transducer assembly.

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