This disclosure relates to sound-producing acoustic receivers and, more specifically, to balanced armature receivers having improved acoustic performance and diaphragms for such receivers.
Balanced armature receivers (also referred to herein as “receivers”) capable of producing an acoustic output signal in response to an electrical input signal are known generally. Receivers typically include a coil disposed about an armature at least a portion of which is movable between permanent magnets retained by a yoke in response to an electrical input signal applied to the coil. These and other components are typically disposed within a housing. The movable portion of the armature is linked to a movable portion of a diaphragm that separates the housing into front and back volumes. Movement of the diaphragm creates an acoustic output signal at an output port of the housing. Such receivers are commonly used in hearing aids, wired and wireless earphones, some of which are known as True Wireless Stereo (TWS) devices, among others. Consumers increasingly expect hearing devices to faithfully reproduce source audio. However current receiver diaphragms are susceptible to bending and resonances that can reduce output and provide less than optimal acoustic performance.
For a more complete understanding of the disclosure, reference should be made to the following detailed description and accompanying drawings wherein:
Those of ordinary skill in the art will appreciate that elements in the figures are illustrated for simplicity and clarity. It will be appreciated further that certain actions and/or steps may be described or depicted in a particular order of occurrence while those having ordinary skill in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein.
The present disclosure relates to balanced armature receivers and diaphragms comprising a paddle for such receivers, wherein the paddle is structured to provide improved acoustic performance as described herein.
According to one aspect of the disclosure, the paddle comprises a material having greater stiffness, in at least one direction, than can be obtained using conventional diaphragm materials, such as aluminum or stainless steel. Increasing the stiffness of the paddle at least along its major dimension improves acoustic performance by reducing bending of the diaphragm and particularly the paddle. The increased stiffness also moves resonances to higher frequencies and permits reducing the height of the diaphragm and thus the overall size of the receiver.
The paddle can be stiffened either by changing its shape or by forming the paddle from a material having a modulus that provides the desired performance. Decreasing the mass of the paddle also increases resonant frequencies of the diaphragm. The specific modulus of a material is equal to Young's modulus/density. Young's modulus is the modulus of elasticity and is equal to the stress/strain of the material. The modulus of the material constituting the paddle can be isotropic or anisotropic. In some implementations, the paddle comprises a material having a specific modulus of at least about 30 MPa/(kg/m3) in at least one dimension of the paddle. In another implementation, the paddle comprises a material having a specific modulus of at least about 28 MPa/(kg/m3) in at least one dimension.
Table I below includes specific modulus data for selected isotropic and anisotropic materials from which the paddle and in some embodiments other parts of the diaphragm can be fabricated. In Table I, carbon fiber and graphene are identified as anisotropic although other known and future materials may also exhibit this property. The other materials in Table I are isotropic. Also, only Aluminum (1145-H19) and Stainless Steel (304) have a specific modulus less than 28 MPa/(kg/m3).
According to another aspect of the disclosure, the paddle comprises a material having a reduced density which reduces the mass of the paddle compared to higher density materials. Reducing the mass of the paddle increases sensitivity, improves frequency response, and reduces the required stiffness of the diaphragm. In some receiver implementations, the paddle comprises a material having a density less than about 2400 kg/m3. However this range may be different depending on the size and geometry of the receiver and diaphragm, among other characteristics thereof. For example, a higher density may be acceptable if weight-reducing slots are formed in the paddle to offset the increased mass associated with the higher density, provided the slotted paddle is sufficiently stiff to prevent bending and other problems associated with lack of stiffness.
In
The receiver housing also comprises a sound port acoustically coupling the front volume to an exterior of the housing. In
The receiver comprises a linkage connecting the movable portion of the armature to the paddle. In
Electric currents representing sounds to be produced are applied to the coil which causes the armature to move between the magnets and causes resulting movement of the paddle in directions 140, shown in
In
The diaphragm comprises a membrane (also referred to herein as a “surround”) covering at least a portion of the diaphragm body and particularly the gap between the paddle and the frame. The membrane generally provides an air barrier between the front and back volumes of the housing and must be suitably flexible or resilient to permit movement of the paddle relative to the frame without undue restraint. The membrane can be a film or layer disposed on, or applied to, all or less than all, of a surface of the diaphragm body. Alternatively, the membrane can be a strip or bead of material disposed on only select portions of the frame and paddle sufficient to cover the gap. The membrane can be made from a highly elastic material (e.g., silicone) or a relatively non-elastic material having a profile and thickness that permits movement of the paddle relative to the frame. Such materials include Mylar, urethane, siloxane, and adhesive, among other known and future materials.
In
In
In
In some implementations, the specific modulus of the paddle is greater along the major dimension of the paddle compared to the minor dimension of the paddle.
In
The material comprising the diaphragm body or at least the paddle thereof can comprise any one or more of carbon fiber or other composites, Mica, AlBeMet 140, AlBeMet 162 H, Beryllium, Graphene, Monolayer carbon (graphene), Bi-layer and poly-layer carbon (graphene) or Carbon nanotubes, binding media (e.g., epoxy or other adhesive) and the like. Advantageously, such candidate materials can provide a light-weight paddle material and enhanced stiffness. In some implementations, only the paddle comprises one or more of these materials and the frame comprises a more conventional material like steel or aluminum. In other implementations, the paddle, frame and hinge comprise the same material or combination of materials.
In one embodiment, at least the paddle comprises a carbon fiber composite. Such composites have a high stiffness to mass ratio, and may have a lower cost than other materials after process refinement. In implementations where the diaphragm body is an assembly of discrete components, the frame can be fabricated from the same or different material than the paddle. The material of the frame, paddle, and hinge will generally be the same for unitary diaphragm bodies. In one embodiment, the paddle is a carbon fiber and the frame is some other material, conventional or otherwise.
While the disclosure and what is presently considered to be the best mode thereof has been described in a manner that establishes possession by the inventor and that enables those of ordinary skill in the art to make and use the same, it will be understood and appreciated that there are many equivalents to the embodiments disclosed herein and that myriad modifications and variations may be made thereto without departing from the scope and spirit of the invention, which are to be limited not by the exemplary embodiments but by the appended claims and their equivalents.
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Number | Date | Country | |
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