The present disclosure relates generally to microphone assemblies and more particularly to microphones with Helmholtz-resonators and other structures for modifying sound input to the microphone assembly.
Microphones are used in various devices including hearing aids, mobile phones, smart speakers, personal computers among other devices and equipment. A microphone generally includes a transducer, and in some devices, an integrated circuit disposed in a housing formed by a can or cover mounted on a base. A sound port typically extends through the base (for a bottom port device) or through the top of the housing (for a top port device). In any case, sound traverses through the sound port and is converted into an electrical signal by the transducer.
For certain applications, the microphone is exposed to ultrasonic frequencies emitted by motion sensors, proximity detectors and other sources. These ultrasonic devices can interfere with the resonance response of the microphone and induce audible artifacts in its output. Thus, users can benefit from improved microphone designs that reduce the adverse effects associated with ultrasonic or other signals otherwise detectable by known microphone assemblies.
The various aspects, features and advantages of the present disclosure will become more fully apparent to those having ordinary skill in the art upon consideration of the following Detailed Description and the accompanying drawings described below.
The disclosure is described in more detail below in connection with the appended drawings and in which like reference numerals represent like components:
According to one aspect of the disclosure, a sensor assembly comprises a housing having an external-device interface and a sound port to an interior of the housing. A transducer is disposed within the housing and acoustically coupled to the sound port. An electrical circuit is also disposed within the housing and electrically coupled to the transducer and to the electrical contacts on the external-device interface. A cavity is formed in a portion of the sensor assembly and acoustically coupled to the interior of the housing via the sound port. The cavity has a wall portion structured to modify an acoustic property of the sensor assembly, such as any one or more of an inertance, resistance, compliance, or resonance. In one example, the sensor assembly is a microphone. In other examples, the sensor assembly includes other sensor types such as a pressure sensor, an accelerometer, a gas sensor, a mass flow sensor, etc.
In various embodiments, the cavity and wall portion form a Helmholtz-resonator that modifies any one or more of a frequency of resonance or an amplitude of resonance of the sound propagating through the sound port. The Helmholtz-resonator is configured with a neck connected to one or more chambers, where the sound port is acoustically coupled to the one or more chambers via the neck.
In some embodiments, the cavity and wall portion forming the Helmholtz-resonator are disposed in a base of the sensor assembly. The base is part of the housing and includes the external-device interface and the sound port. In one implementation, the neck and the one or more chambers are formed in or on a same layer of the base. In another implementation, the neck and the one or more chambers are formed in or on different layers of the base, with the neck being formed in or on a first layer and the one or more chambers being formed in or on a second different layer. Other suitable neck and chamber implementations may be contemplated in other embodiments.
In certain embodiments, the cavity and wall portion forming the Helmholtz-resonator are disposed in a sound port adapter that can be fitted to the sensor assembly. The sound port adapter includes an acoustic channel acoustically coupled to the cavity. The sound port adapter includes a sound outlet and a sound inlet disposed on a mounting surface. The sound outlet is acoustically coupled to the sound port when the mounting surface is coupled to a surface (e.g., base) of the sensor assembly.
According to another aspect of the disclosure, a sound port adapter for a microphone assembly comprises a body member having a mounting surface and an acoustic channel disposed through the body member. The acoustic channel includes a sound inlet and a sound outlet. The body member is configured to mount on a surface (e.g., top or bottom surface) of the microphone assembly on which a sound port is disposed. A Helmholtz-resonator comprising a neck and one or more chambers is disposed in the body member. The acoustic channel is acoustically coupled to the one or more chambers by the neck.
In some embodiments, the body member includes a wall portion configured to form a non-straight acoustic path in the acoustic channel to modify any one or more of an inertance or resistance of the acoustic channel. In other embodiments, the body member includes a wall portion configured to obstruct the entry of debris into the acoustic channel for ingress protection.
In various applications, a sound attenuation device, such as a Helmholtz-resonator, can be employed to reduce or dampen the acoustic signal at specific frequencies (e.g., high frequencies) at the input of the microphone or other sensor.
A sensor assembly generally includes various components enclosed in a housing.
The transducer is configured to convert sound into an electrical signal. Once converted, the electrical circuit conditions the electrical signal before providing the conditioned signal at the external-device interface. Such conditioning may include buffering, amplification, filtering, analog-to-digital (A/D) conversion for digital devices, and signal protocol formatting among other processing. The microphone assembly of
To modify an acoustic property of the microphone assembly, a tuning structure may be formed in a portion of the microphone assembly. In
As shown in
The neck acoustically couples the sound port to the two chambers. As shown in
While a microphone is shown in
Different techniques can be employed to embed the Helmholtz-resonator in the base of the microphone assembly. The base may be comprised of various layers of material (e.g., FR-4, epoxy, plastic, ceramic, glass fiber, etc.). In
In certain embodiments, instead of having the tuning structure in the base of the sensor assembly, a sound port adapter may be configured with the tuning structure to modify various acoustic properties (e.g., inertance, resistance, compliance and/or resonance) of the sensor assembly.
The body member includes a Helmholtz-resonator formed by the cavity and wall portion. Here, the wall portion includes wall segments 514, 516 that extend horizontally (e.g., parallel with respect to the sound inlet) into the cavity to define the neck of the Helmholtz-resonator. The chamber of the Helmholtz-resonator is defined by the two wall segments and a third sidewall 518. In this manner, the acoustical channel is acoustically coupled to the chamber by the neck. The chamber is shown to have rounded corners 520, 522, although other shapes may be considered. While one rectangularly-shaped chamber is shown in
To facilitate mounting of the sound port adapter, a surface 602 of the housing on which the sound port is disposed may include a ground plane 604. The shape of the ground plane can correspond to the sidewalls of the sound port adapter such that the sidewalls can be attached to the ground plane (e.g., by using solder or cement). The surface may also include a plurality of contacts pads 606-610 (e.g., supply voltage, clock, data, etc.) for the external-device interface.
In
The discrete wall portions are arranged in spaced-apart relation with the distance between each of the discrete wall portions being adjustable as desired. The space between each of the discrete wall portions forms the sound inlet to allow sound to travel to the sound outlet. This arrangement also acts like a mesh or screen to prevent debris from entering the acoustic channel.
In
The sound inlet is narrowed by the placement of the wall segment 908 with respect to the sidewall 509. This arrangement of also defines a non-straight path 912 with three turns for the sound to follow from the sound inlet to the sound outlet. In general, the wall portion may be configured with various wall segments to form any type of non-straight path (e.g., spiral path, twisting path, S-shape path, sinusoidal path, zigzag path, serpentine path, etc.) to modify the inertance of the acoustic channel and to obstruct debris from entering the acoustic channel.
The cylindrical pillars are located near the sound outlet and disposed vertically between the wall segments 902 and 906. In other examples, the cylindrical pillars may be located near the sound inlet. Other configurations of a tortuous acoustic channel with one or more discrete wall portions may be contemplated in other embodiments.
Among other advantages, employing a Helmholtz-resonator near the entry port of a microphone or another sensor can serve to tune the resonance response the device to thereby improve the quality of the output signal. Other benefits will be recognized by those of ordinary skill in the art.
While the present disclosure and what is presently considered to be the best mode thereof has been described in a manner that establishes possession by the inventors 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 exemplary embodiments disclosed herein and that myriad modifications and variations may be made thereto without departing from the scope and spirit of the disclosure, which is to be limited not by the exemplary embodiments but by the appended claims.
This application claims priority to U.S. Provisional Patent Application Ser. No. 62/954,918 filed on Dec. 30, 2019, entitled “Helmholtz-Resonator for Microphone Assembly,” the entire contents of which are hereby incorporated by reference.
Number | Date | Country | |
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62954918 | Dec 2019 | US |