Patent Application
20230217175
The present disclosure relates generally to balanced armature (BA) receivers and more particularly to balanced armature receivers having improved frequency response, diaphragms and components for such balanced armature receivers.
Balanced armature receivers (also referred to herein as “receivers” and “BAs”) capable of producing an acoustic output signal in response to an electrical audio signal are commonly used in hearing aids, wired and wireless earphones, and True Wireless Stereo (TWS) devices, among other hearing devices. BA receivers generally comprise a housing in the form of a cup and cover enclosing a diaphragm that separates an interior of the housing into a back volume and a front volume. An electromagnetic motor includes an electrical coil disposed about an armature (also referred to herein as a “reed”) having a free end portion movably disposed between permanent magnets retained by a yoke. A drive rod or other link mechanically connects the reed to a movable part of the diaphragm known as a paddle. The reed vibrates between the magnets when an electrical signal (representing sound) is applied to the coil, otherwise the reed is balanced between the magnets. The moving diaphragm expels sound out of a sound port of the housing via the front volume.
A plot of the BA receiver output sound pressure level (SPL) typically in decibels (dB) versus frequency in hertz (Hz) is referred to herein as the “frequency response”. The acoustic output of the receiver is generally not uniform across all audible frequencies and includes multiple amplitude peaks attributable to mechanical and acoustic resonances. Some of the frequency response peak are predominately attributable to the user's ear canal or to portions of the hearing device coupling the receiver to the ear canal. Another peak is predominately attributable to the diaphragm and more particularly to a bending mode of the paddle. This bending-mode peak typically has a frequency higher than a peak attributable to the user's ear.
An industry-standard ear-simulator is often used for modeling receivers worn by a user. One such simulator is specified by the International Electrotechnical Commission (IEC) 60318-4 standard and is known as a high-resolution 711 coupler. Other simulators can also be used to model receiver performance. Receiver performance is typically measured with the receiver coupled to a coupler, but the frequency response peaks may shift and other peaks may arise when the receiver is actually integrated with a hearing device. Such changes are generally attributable to the acoustic output path or acoustic impedances resulting from the unique structure of the hearing device, among other factors.
In some receivers (e.g., in tweeters) higher SPL peaks may exist at frequencies above the audible range of many users. Such peaks can be attributable to a bending-mode of the paddle, among other causes. For example, some people cannot hear frequencies higher than 18 kHz or less. A diaphragm resonator can shift resonance of these higher frequency peaks to a limited extent, but a resonator alone may be unable to shift the resonance to frequencies perceptible by some people. Thus, there is a desire to provide receivers having improved frequency performance.
The objects, features and advantages of the present disclosure will become more fully apparent from the following detailed description and the appended claims considered in conjunction with the accompanying drawings. The drawings depict only representative embodiments and are therefore not considered to limit the scope of the disclosure.
Those of ordinary skill in the art will appreciate that the figures are illustrated for simplicity and clarity and therefore may not be drawn to scale and may not include well-known features, that the order of occurrence of actions or steps may be different than the order described or be performed concurrently unless specified otherwise, and that the terms and expressions used herein have the meaning understood by those of ordinary skill in the art except where different meanings are attributed to them herein.
The disclosure relates generally to balanced armature receivers and more particularly to balanced armature receivers having improved frequency response, as well as balanced armature receiver diaphragms and components for such receivers.
The diaphragm generally comprises a paddle movable relative to a frame disposed about a periphery of the paddle. A gap separates the paddle from the frame and a flexible or elastic film covers the gap and permits the paddle to move relative to the frame when driven by a motor of the receiver. The film can cover the entire paddle and frame or only regions of the paddle and frame adjacent to the gap. The film can also cover any mass-reducing apertures in the paddle in embodiments where such apertures are present. In some receiver implementations, the diaphragm includes a barometric relief vent through the paddle, film or frame to equalize pressure in the back volume. In these implementations, the back volume vents to the exterior of the housing via the front volume. Alternatively, the barometric relief vent can be located in a wall portion of the housing defining the back volume wherein the back volume vents directly to an exterior of the housing instead of to the exterior of the housing via the front volume.
Generally, the receiver includes a motor disposed in the housing for actuating the diaphragm. In
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Paddles used in BA receivers configured for in-ear and on-ear applications can be formed from a sheet material having a thickness between 0.03 mm and 0.07 mm. As suggested, other portions of the diaphragm can also be fabricated from the same sheet material. The thickness of other receiver paddles may be outside this range. Additionally, the overall thickness of a paddle comprising a sheet material shaped to form a stiffening-rib may be thicker than the thickness of the sheet material. In these and other paddles, the paddle has an effective modulus not less than 30 GPa. The effective modulus for sheet material can be characterized by its flexural modulus (also known as the bending modulus or bending modulus of elasticity), which is a mechanical property that measures a material's stiffness or resistance to bending. The effective modulus is less for sheet materials having an array of apertures, holes, or openings, compared to the same sheet, made of the same alloy or composite, that does not contain apertures, holes, or openings. The flexural modulus is expressed as a ratio of stress to strain and the standard unit of measure is the Pascal (Pa or N/m2).
According to one aspect of the disclosure, a balanced armature receiver diaphragm comprises a paddle having an area of concentrated mass located between opposite ends of the paddle and between opposite sides of the paddle (e.g., in or near a central portion of the paddle). The area of concentrated mass has an area density greater than an area density of other portions of the paddle. The “area density” for the purposes of this disclosure means the mass of a portion of the paddle (e.g., the area of concentrated mass) divided by the area of that portion of the paddle. In one implementation, the area density of the area of concentrated mass is at least twice the area density of other portions of the paddle. In another implementation, the area density of the area of concentrated mass is at least thrice the area density of other portions of the paddle. In another implementation, the area density of the area of concentrated mass is at least six times the area density of other portions of the paddle. In one implementation, the area of concentrated mass comprises at least 10% of a total mass of the paddle. In another implementation, the area of concentrated mass comprises at least 25% of a total mass of the paddle. In another implementation, the area of concentrated mass comprises at least 40% of a total mass of the paddle. In the diaphragm implementations described herein, the paddle can be devoid of a resonator. In other implementations, the diaphragm and particularly the paddle includes a resonator in combination with an area of concentrated mass.
The area density of the area of concentrated mass can be increased by adding material to the area of concentrated mass or by removing material from portions of the paddle other than the area of concentrated mass, or by a combination thereof. Representative examples are described further herein.
In some implementations, a discrete element contributes to the area of concentrated mass on the paddle. The discrete element can have various different shapes, representative examples of which are described herein. The discrete element can be located on a top or bottom surface of the paddle, or on both the top and bottom surfaces of the paddle. The discrete element can be retained on the paddle by an adhesive, epoxy weld, rivet, crimp or other fastening mechanism. In
Alternatively, the area of concentrated mass can be an area of the paddle having increased thickness compared to other portions of the paddle. The increased thickness can be material located on the top side, bottom side, or on both the top and bottom sides of the paddle. Such a paddle can be an unassembled unitary member made in casting, coining, or additive manufacturing operations, among others. In these implementations, the area density of the area of concentrated mass is attributable, at least in part, to the additional material integrated into the paddle.
In other implementations, the paddle includes a plurality of mass-reducing apertures in portions of the paddle other than the area of concentrated mass. The mass reduction of the paddle can be optimized by selecting the size and shape of the apertures and by appropriately distributing the apertures about the paddle. Such apertures can be formed in stamping, milling, casting or additive manufacturing operations, among others. In these implementations, the area density of the area of concentrated mass is attributable, at least in part, to fewer apertures (if any) per unit area in the area of concentrated mass compared to the apertures per unit area in the other portions of the paddle. In some implementations, there are no apertures in the area of concentrated mass. The mass of the paddle with or without apertures can also be reduced by appropriate selection of the material and dimensions of the paddle.
In other implementations, the paddle can include apertures in combination with material added to the area of concentrated mass as described above. In
Table I below includes a non-exhaustive list of representative materials from which the paddle, other portions of the diaphragm, and the discrete or integrated element contributing to the area density of the area of concentrated mass can be fabricated. The values in Table I are approximate and may vary by exact material composition and geometry or shape. Also materials having a lower density or smaller thickness may be used where a lesser reduction in the frequency of the frequency response peak is desired.
In one implementation, the area of concentrated mass comprises a material having a density greater than 2.7 grams per cubic centimeter (g/cm3). In other implementations, the area of concentrated mass comprises a material having a density of more than 7.0 g/cm3 (e.g., stainless steel) or more than 13.0 g/cm3 (e.g., tungsten carbide). In some implementations, the area of concentrated mass has an area density over 10 mg/cm2. For example, a 0.05 mm thick solid aluminium sheet is about 13.5 mg/cm2. In one implementation, the area of concentrated mass has an area density of more than 50 mg/cm2. In another implementation, the area of concentrated mass has an area density more than 100 mg/cm2. In another implementation, the area of concentrated mass has an area density greater than 200 mg/cm2. For example, a 0.05 mm thick stainless steel sheet fastened to a 0.05 mm thick aluminium sheet has an area density of about 53 mg/cm2, a 0.14 mm thick stainless steel sheet fastened to a 0.05 mm thick aluminium sheet has an area density of about 124 mg/cm2, and a 0.14 mm thick tungsten carbide sheet fastened to a 0.05 mm thick aluminium sheet has an area density of about 224 mg/cm2. The foregoing representative examples are non-exhaustive and non-limiting.
Increasing the overall mass of the paddle increases the total moving mass of the receiver in operation and can lower the frequency of the first peak or other frequency response peaks below the peak predominately attributable to the diaphragm. Increasing the overall mass of the paddle can also decrease the amplitude of the response after the first peak. Therefore, it is generally preferred not to increase the overall mass of the paddle. The overall mass of the paddle can be increased only slightly, maintained at approximately the same value, or even reduced while still having the desired effects on the frequency response peak attributable predominately to the diaphragm by adding mass only to the area of concentrated mass. The mass increase in the area of concentrated mass can be offset by adding mass-reducing apertures to the paddle, by using a lower density material for the paddle, or by using a thinner material, among other means of reducing the overall mass of the paddle. The overall mass of the paddle may even be reduced using one of these or other mass reducing schemes.
Generally, the area density of the area of concentrated mass and the overall mass of the paddle affect the frequency response of the balanced armature receiver. More particularly, the area density of the area of concentrated mass affects the frequency response peak attributable predominately to the diaphragm. Increasing the mass of the area of concentrated mass tends to decrease the frequency of the frequency response peak predominately attributable to the diaphragm. Increasing the mass of the area of concentrated mass on the paddle also tends to increase the amplitude of the peak predominately attributable to the diaphragm. Conversely, decreasing the mass of the area of concentrated mass tends to increase the frequency of the frequency response peak predominately attributable to the diaphragm. Decreasing the mass of the area of concentrated mass on the paddle also tends to decrease the amplitude of the peak predominately attributable to the diaphragm. Representative frequency response plots are described below.
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While the disclosure and what is presently considered to be the best mode thereof has been described in a manner establishing possession and enabling 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 representative embodiments described herein and that myriad modifications and variations may be made thereto without departing from the scope and spirit of the invention, which is to be limited not by the embodiments described but by the appended claims and their equivalents.
| Number | Date | Country | |
|---|---|---|---|
| 63295321 | Dec 2021 | US |
