Load change diagnostics for acoustic devices and methods

#This application relates to U.S. Provisional Patent Application Ser. No. 62/409,341 filed on Oct. 17, 2016, and entitled “Armature-Based Acoustic Receiver Having Improved Output and Method,” the entire content of which is hereby incorporated by reference.

#This disclosure relates generally to acoustic devices and more specifically to acoustic load change diagnostics in acoustic devices, electrical circuits therefor and corresponding methods.

#Acoustic devices including a balanced armature receiver that converts an electrical input signal to an acoustic output signal characterized by a varying sound pressure level (SPL) are known generally. Such devices may be embodied as hearing aids, headsets, or ear buds worn by a user. The receiver generally comprises a motor having a coil to which an electrical excitation signal is applied. The coil is disposed about a portion of an armature (also known as a reed), a movable portion of which is disposed in equipoise between magnets, which are typically retained by a yoke. Application of the excitation or input signal to the receiver coil modulates the magnetic field, causing deflection of the reed between the magnets. The deflecting reed is linked to a movable portion of a diaphragm (known as a paddle) disposed within a partially enclosed receiver housing, wherein movement of the paddle forces air through a sound outlet or port of the housing. The performance of such acoustic devices may be adversely affected by sub-optimal coupling, or obstruction of the acoustic output signal, among other conditions tending to change the acoustic load coupled to the device.

#FIG. 1 is a block diagram of a system for generating a pre-distorted excitation signal for input to an armature-based receiver.

#FIG. 2 is a graph of total harmonic distortion (THD) versus SPL for different magnetizations and for different types of input or excitation signals without pre-distortion.

#FIGS. 3A-3D are a comparative illustration of a receiver output in response to input signals with and without pre-distortion.

#Those of ordinary skill in the art will appreciate that elements in the figures are illustrated for simplicity and clarity. It will be further appreciated that certain actions or steps may be described or depicted in a particular order of occurrence while those of ordinary skill in the art will understand that such specificity with respect to sequence is not actually required unless a particular order is specifically indicated. 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 fields of inquiry and study except where specific meanings have otherwise been set forth herein.

#Generally, acoustic devices and methods are disclosed for producing an acoustic output signal in response to an electrical input signal. The transduction of the electrical input signal may be performed by an acoustic receiver (also referred to herein as a “receiver”). In one embodiment, the receiver is embodied as an armature-based receiver comprising an armature linked to a diaphragm that separates a receiver housing into a front volume and a back volume, wherein the front volume is coupled to an output port of the housing by an acoustic passage. In some embodiments the acoustic passage includes a spout on which the output port is disposed. In other embodiments, the acoustic passage includes a chamber (also referred to as a doghouse) between the front volume and the output port of the receiver. In other embodiments, the receiver is embodied as a dynamic speaker comprising a diaphragm that separates a receiver housing into a front volume and a back volume. The acoustic device may be embodied as a receiver or as a receiver integrated with some other device like a hearing aid, a headset, an earbud or earpiece or as some other device that produces an acoustic output signal in response to an electrical input signal and is intended for use in close proximity to a user's ear.

#According to one aspect of the disclosure, the acoustic output signal of the receiver is converted to an electrical output signal that is related to a sound pressure of the acoustic signal using one or more electro-acoustic transducers (e.g., microphones) located in, on, or near the acoustic device. In one embodiment, the receiver device includes at least one microphone positioned to detect sound pressure in at least one of the front volume, the back volume, or the output passage of the receiver. There may be differing advantages to locating microphones to sense sound pressure in different areas of the receiver as described herein. In some implementations, sound pressures detected in multiple location of the receiver housing are also used to determine the load change.