Amplified reactance filter for transducer ultrasound

Abstract

The invention relates to an amplified reactance filter for transducer ultrasound. A reactance filter assembly includes a reactance filter acoustically coupled to a transducer operable to generate an audio frequency by air non-linear demodulation of an ultrasonic frequency, the reactance filter having a plurality of auditory conductive pathways tuned to introduce a radiation impedance to the transducer, therefore, the efficiency of the transducer is improved.

Description

[0001] Cross Reference to Related Applications This application is a non-provisional of co-pending U.S. Provisional Patent Application No. 63 / 674,684, filed July 23, 2024, and U.S. Provisional Patent Application No. 63 / 811,325, filed May 23, 2025, both of which are incorporated by reference herein. TECHNICAL FIELD

[0002] One aspect of the present disclosure relates to a reactance filter that improves the efficiency of a transducer configured to generate audio frequencies by ultrasonic frequency air non-linear demodulation. Other aspects are also described and claimed. BACKGROUND

[0003] Portable communication or listening devices (e.g., smart phones, earphones, etc.) have one or more transducers located within them that convert input electrical audio signals to sound pressure wave outputs that can be heard by a user or convert sound pressure wave inputs to electrical audio signals. Transducers (e.g., speakers) can be used, for example, to output sound pressure waves corresponding to a far-end user’s voice, such as during a phone call, or to output sound pressure waves corresponding to sounds associated with a game a user wants to play or music a user wants to play. Because the profile of portable devices is relatively thin, the profile of the transducers is also relatively thin, which in turn can make it difficult to maintain optimal sound quality. Moreover, for health and safety reasons, it can be desirable to attenuate certain ultrasonic amplitudes or frequency ranges output by the transducers or otherwise output near a user’s ear, while still outputting lower frequencies to the user’s ear. SUMMARY

[0004] Aspects of the present disclosure relate to a reactance filter that improves the efficiency of a transducer configured to generate audio frequencies through air nonlinearity demodulation of ultrasonic frequencies. For example, the transducer can be a microelectromechanical system (MEMS) transducer that uses ultrasonic frequencies to generate audio frequencies. Typically, a MEMS transducer or speaker can use ultrasonic modulation and demodulation techniques to generate audible sound. For example, a MEMS transducer can generate ultrasonic frequencies, and then air nonlinearity in the environment outside of the transducer demodulates the ultrasonic frequencies into audio frequencies or audio sound output. In this regard, the ultrasonic frequency demodulation and generation of audible sound from the transducer output occurs outside of the transducer. It can also be appreciated that changing or altering the air impedance and, in turn, the radiation impedance of the transducer, changes or alters the efficiency (e.g., sound output) of the transducer. For example, increasing the air or radiation impedance can amplify the ultrasonic frequencies output by the transducer, which in turn amplifies or enhances the audio frequencies or sound waves output by the transducer, thus improving the efficiency. Accordingly, a reactance filter can be coupled to the output port of the transducer to introduce radiation impedance to the transducer, which in turn can improve the transducer efficiency. For example, without the reactance filter, the radiation impedance can be low, and the air nonlinearity generates a certain audio output from the ultrasonic frequencies output by the transducer. Adding the reactance filter to the transducer increases the radiation impedance, which in turn amplifies the ultrasonic frequencies output by the transducer, and can significantly amplify the audio output generated from the ultrasonic frequencies. For example, in some aspects, without the reactance filter, the transducer can have an ultrasonic frequency output (e.g., greater than 20 kHz) of about 115 decibels (dB) and an audible frequency output (e.g., 20 Hz to about 20 kHz) of about 50 dB. When the reactance filter is added, the ultrasonic frequency output can increase to 122 dB, and this 7 dB increase can translate to almost a 20 dB gain in the audio frequency output.

[0005] In this regard, the reactance filter can have a geometry comprising a plurality of auditory conduction pathways, where the geometry is tuned to introduce a radiation impedance to the transducer for amplifying or enhancing the audio output. For example, in some aspects, each of the auditory conduction pathways can comprise at least two different cross-sectional dimensions. For example, each auditory conduction pathway can comprise a sound cavity having one cross-sectional dimension and a neck coupling the sound cavity to the transducer and having a different cross-sectional dimension. In some aspects, the sound cavity can have a larger cross-sectional dimension than the neck. Further, in still other aspects, each auditory conduction pathway can further comprise another neck coupling the sound cavity to an attenuator configured to attenuate the ultrasonic frequencies output by the transducer once the audio frequencies are generated, such that the ultrasonic frequencies are not output to the user. It should also be appreciated that while the term "filter" is used, the "reactance filter" does not actually remove or otherwise separate out unwanted components. Rather, the reactance filter is a reactance component or amplifier configured to alter the radiation impedance of the transducer to improve transducer efficiency (e.g., amplify the sound output), as discussed herein.

[0006] In some aspects, a reactance filter assembly is provided that includes a reactance filter acoustically coupled to a transducer, the transducer operable to generate audio frequencies by air non-linear demodulation of ultrasonic frequencies, the reactance filter having a plurality of auditory conduction pathways tuned to introduce a radiation impedance to the transducer to improve transducer efficiency. In some aspects, the reactance filter increases the radiation impedance to the transducer to improve transducer efficiency. In still other aspects, the radiation impedance results in an amplified ultrasonic frequency output that brings a gain to the audio frequency output. In some aspects, the reactance filter comprises a low pass filter. In some aspects, each of the plurality of auditory conduction pathways comprises a sound cavity, a second neck, and a first neck coupling the sound cavity to the transducer. In other aspects, the sound cavity has a cross-sectional dimension that is larger than cross-sectional dimensions of the first neck and the second neck. In still other aspects, the first neck and the second neck have the same cross-sectional dimension, and the sound cavity has a cross-sectional dimension that is larger than the cross-sectional dimensions of the first neck and the second neck. In other aspects, the second neck couples the sound cavity to an attenuator configured to attenuate the ultrasonic frequencies output by the transducer with the audio frequencies.

[0007] In other aspects, the transducer assembly includes a transducer operable to generate an audio frequency by air non-linear demodulation of an ultrasonic frequency and a reactance filter assembly coupled to the transducer and having an auditory conduction pathway including a first cross-sectional dimension and a second cross-sectional dimension, the auditory conduction pathway tuned to introduce a radiation impedance to the transducer to improve transducer efficiency. In some aspects, the reactance filter assembly increases the radiation impedance to the transducer to improve the transducer efficiency. In other aspects, the radiation impedance causes an amplified ultrasonic frequency output that brings a gain to an audio frequency output. In yet other aspects, the reactance filter assembly includes a low pass filter. In other aspects, the first cross-sectional dimension defines an acoustic cavity and the second cross-sectional dimension defines a second neck and a first neck coupling the acoustic cavity to the transducer. In yet other aspects, the first cross-sectional dimension of the acoustic cavity is greater than the cross-sectional dimensions of the first and second necks. In other aspects, the second neck couples the acoustic cavity to an attenuator configured to attenuate the ultrasonic frequency output by the transducer with the audio frequency. In some aspects, the auditory conduction pathway is a first auditory conduction pathway and the reactance filter assembly includes a second auditory conduction pathway. In some aspects, the transducer includes a microelectromechanical system speaker.

[0008] In some aspects, a portable electronic device includes a device housing having a housing wall defining an internal chamber separate from a surrounding environment, a transducer positioned within the internal chamber and operable to generate an audio frequency by air non-linear demodulation of an ultrasonic frequency, and a reactance filter assembly coupled to the transducer and having a plurality of auditory conduction pathways tuned to introduce a radiation impedance to the transducer to improve transducer efficiency. In other aspects, the reactance filter assembly increases the radiation impedance to the transducer to improve the transducer efficiency. In some aspects, the radiation impedance causes an amplified ultrasonic frequency output that brings a gain to an audio frequency output. In other aspects, the reactance filter assembly includes a low pass filter. In some aspects, each auditory conduction pathway of the plurality of auditory conduction pathways includes an acoustic cavity, a second neck, and a first neck coupling the acoustic cavity to the transducer. In other aspects, a cross-sectional dimension of the acoustic cavity is greater than cross-sectional dimensions of the first and second necks. In yet other aspects, the first and second necks have the same cross-sectional dimension and the acoustic cavity has a cross-sectional dimension greater than the cross-sectional dimensions of the first and second necks. In some aspects, the second neck couples the acoustic cavity to an attenuator configured to attenuate the ultrasonic frequency output by the transducer with the audio frequency.

[0009] The above summary does not include an exhaustive list of all aspects of the present disclosure. It is expected that the present disclosure described herein will encompass all systems and methods falling within the scope of the following claims, both individually and in all possible combinations. Such combinations are contemplated to have specific advantages not recited herein. BRIEF DESCRIPTION OF DRAWINGS

[0010] Various aspects are illustrated by way of example, and not limitation, in the accompanying drawings, in which like reference numerals indicate similar elements, wherein:

[0011] Figure 1 A cross-sectional side view illustrating one aspect of an electronic device in which a

[0012] Figure 2 An enlarged cross-sectional side view illustrating one aspect of an electronic device in which a Figure 1

[0013] Figure 3 An isometric cutaway view illustrating one aspect of an electronic device in which a Figure 1

[0014] Figure 4 A block diagram illustrating one aspect of an electronic device in which a Figures 1 to 3 DETAILED DESCRIPTION

[0015] In this section, we will explain several preferred aspects of the present disclosure with reference to the accompanying drawings. Whenever a described component's shape, relative position, and other aspects are not clearly defined, the scope of the present disclosure is not limited only to the illustrated components, which are shown only for illustrative purposes. In addition, although many details are set forth, it is understood that some aspects of the present disclosure can be practiced without these details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure the understanding of this description.

[0016] ​​​The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting of the present disclosure. Spatially relative terms, such as "under", "below", "lower", "on", "above", "upper", and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device is inverted in the figure, a spatially relative term such as "below" or "under" can be interpreted to mean "above" or "over" in view of the device being inverted. Thus, a term such as "below" can encompass both an orientation of above and below. The device can be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0017] As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising", when used in this specification, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0018] The terms "or" and "and / or" as used herein are to be interpreted as inclusive or meaning any one or any combination. Therefore, "A, B or C" or "A, B and / or C" means "any of the following: A; B; C; A and B; A and C; B and C; A, B and C." An exception to this definition will occur only when two elements are inherently mutually exclusive from each other.

[0019] Figure 1A cross-sectional side view of one aspect of a reactance filter assembly is illustrated. The reactance filter assembly 100 can include a housing or shell 102 having one or more walls or portions that are sealed together to form an internal cavity or chamber 106 that is separate from the surrounding environment 104. The housing or shell 102 can be a relatively rigid structure that forms an electronic device housing. Representatively, in some aspects, the housing or shell 102 can form a headphone or wearable device housing. In some aspects, these portions or walls can be considered fixed structures that can be snap fit, welded, adhered, or attached together in a sealed manner to form the desired type of shell 102. The internal chamber 106 defined by the shell 102 can include a transducer 124 that is configured to generate audible sound that can be output to the surrounding environment 104 and, more particularly, to the ear of a nearby user. In some aspects, the transducer 124 can be a microelectromechanical system (MEMS) transducer or speaker that uses ultrasonic modulation and demodulation techniques to generate audible sound. For example, the MEMS transducer can generate an ultrasonic frequency 120 that is then demodulated to an audio frequency or audio sound output 122 by the non-linearity of the air in the environment outside of the transducer. In this regard, the ultrasonic frequency demodulation and generation of audible sound from the transducer output occurs outside of the transducer. Moreover, as previously discussed, changing or altering the air impedance and, in turn, the radiation impedance of the transducer alters or changes the efficiency of the transducer (e.g., sound output). For example, increasing the air or radiation impedance can amplify the ultrasonic frequency output by the transducer, which in turn amplifies or enhances the audio frequency or sound wave output by the transducer, thus improving the efficiency. Accordingly, the reactance filter 130 can be coupled to the output port 125 of the transducer 124 to introduce a radiation impedance to the transducer 124 that, in turn, can improve the transducer efficiency. For example, the reactance filter 130 can have a geometry that increases the radiation impedance of the transducer 124, which in turn amplifies the ultrasonic frequency output by the transducer 124 and can significantly amplify the audio output 122 generated from the ultrasonic frequency. In some aspects, the reactance filter 130 can be, for example, a low pass filter that is not used to filter certain frequencies, but is configured to introduce additional radiation impedance to the transducer 124 to improve the overall efficiency of the transducer 124. Reference will be made to Figure 2 The specific geometry of the reactance filter 130 is described in more detail.

[0020] However, in addition to audible sound, there can also be ultrasonic frequencies that are output by the transducer 124 to the ambient environment. To reduce the output of ultrasonic frequencies to the ambient environment, and more particularly to the vicinity of the ear, an attenuator 108 can be coupled to the reactance filter 130. The attenuator 108 can be configured to attenuate undesirable ultrasonic frequencies output by the transducer 124 before reaching the ambient environment 104. Representatively, the attenuator 108 can be connected at one end to the output port 132 of the reactance filter 130 and configured to output or otherwise leak audible or desirable sound 122 to the ambient environment 104 while attenuating or otherwise preventing the output of undesirable ultrasonic waves or frequencies 120. Representatively, the attenuator 108 can be formed by one or more walls 110, 112, 114, 116 connected to the housing 102 and defining a sound cavity 107. For example, the attenuator 108 can include a side wall 110 and a side wall 116 that extend parallel to each other and are connected by an end wall 114 that closes or otherwise seals an end of the sound cavity 107. Another end wall 112 of the attenuator 108 can be open or otherwise form an opening and coupled to the reactance filter 130. The transducer 124 can output sound waves 120 in the ultrasonic frequency range to the reactance filter 130, which can then amplify the ultrasonic waves 120 and output them to the sound cavity 107 of the attenuator 108, where air nonlinearity converts the ultrasonic waves 120 into sound waves 122 in the audible frequency range. The attenuator 108 can also include a plurality of openings 118A, 118B, 118C between the sound cavity 107 and the ambient environment 104 to output audible sound or waves to the ambient environment 104 (e.g., to the ear of a nearby user). The openings 118A-118C can be formed at locations and / or positions along the side wall 110 of the attenuator 108 that are selected to output or otherwise leak audible or desirable sound waves to the ambient environment 104 through the openings 118A-118C while attenuating or otherwise preventing the leakage of undesirable ultrasonic frequencies through the openings 118A-118C. To attenuate these undesirable ultrasonic frequencies, the attenuator 108 can have a length that is an integer (N) multiple of the wavelength of the frequency of the carrier and / or modulator frequencies represented by the sound waves 120. The sound waves 120 (e.g., representing ultrasonic frequencies) form a longitudinal wave within the sound cavity 107 that has a pressure minimum represented by a valley or zero point 120A and a pressure maximum represented by a peak 120B along its length. This pattern can be referred to as a standing wave because the traveling wave coincides with the reflected wave at the same location with the same time interval over the length. In comparison to the ultrasonic frequencies, the sound waves 122 within the sound cavity 107 can be in the audible or relatively low frequency range such that the pressure minimum or zero point 122A and the pressure maximum or peak 122B of the waves 122 will not share all of the same locations as the ultrasonic waves 120.Conversely, the sound wave 122 can have pressure maxima or peaks 122B at locations along the attenuator 108 that coincide with some of the pressure minima or nulls 120A of the sound wave 120, as shown. At the pressure minima, there will be no or only minimal energy flow (e.g., near zero pressure), while at the pressure maxima there will be maximal energy flow. Thus, as shown, forming the openings 118A-C at locations along the attenuator sidewall 110 that coincide with the pressure minima 120A of the high frequency wave 120 (e.g., ultrasonic frequency wave) and the pressure maxima of the low frequency wave 122 (e.g., audible frequency wave) will allow the desired audible tone represented by the low frequency wave 122 to leak from the openings 118A-C without leaking the ultrasonic frequency represented by the wave 120 through the openings 118A-C, or only minimally leaking the ultrasonic frequency represented by the wave. In this regard, the attenuator 108 outputs audio tones (e.g., in the audible frequency range) from the transducer 124 and amplified using the filter 130 to the ambient environment 104, while attenuating the undesired ultrasonic frequency (e.g., in the ultrasonic frequency range). It should be appreciated that the attenuator 108 is one representative attenuator, however, any other type of attenuator suitable for attenuating ultrasonic frequencies can be coupled to the filter 130. Further, it should be appreciated that in some aspects, the openings 118A-C can not be open all the way to the closed end 114 of the attenuator 108. Rather, to support standing wave buildup inside the attenuator 108, one or both of the openings 118A-C, e.g., openings 118B and 118C, can be closed. This helps the standing wave reach a higher pressure gradient between the peaks and nulls, allowing air non-linear demodulation to become more efficient in the demodulation.

[0021] Reference is now made to Figure 2 , Figure 2 Illustrated Figure 1FIG. 6 is an enlarged cross-sectional side view of the reactive filter assembly of FIG. 5. From this view, it can be seen that the reactive filter assembly 130 can include a plurality of auditory conduction pathways 202A, 202B, 202C, 202D, 202E, 202F, 202G, 202H, 202I that are acoustically coupled at one end to the transducer 124 and at the other end to the attenuator 108. Each of the auditory conduction pathways 202A-202I can have a geometry that is tuned to introduce a radiation impedance into the transducer 124 and to increase or otherwise improve the efficiency of the transducer 124. Typically, in some aspects, the auditory conduction pathways 202A-202I can be composed of segments or portions having different cross-sectional dimensions D1 and D2. For example, in some aspects, the auditory conduction pathways 202A-202I can include a neck portion 204 having a cross-sectional dimension D1, a sound cavity portion 206 having a cross-sectional dimension D2, and another neck portion 208 having a cross-sectional dimension D2. The cross-sectional dimension D1 of the neck portions 204, 208 can be the same and can be narrower or smaller than the cross-sectional dimension D2 of the sound cavity portion 206. In other words, the cross-sectional dimension D2 of the sound cavity portion 206 can be wider or larger than the cross-sectional dimension D1 of the neck portions 204, 208. In some aspects, the neck portion 204 can extend from one side of the sound cavity 206 and connect the sound cavity 206 to the acoustic output port of the transducer 124. The neck portion 208 can extend from the opposite side of the sound cavity 206 and connect the sound cavity 206 to the attenuator 108. In this regard, the ultrasonic frequency waves 120 output by the transducer 124 can pass through the neck portion 204 to the sound cavity 206 and then out of the neck portion 108 of each of the auditory conduction pathways 202A-202I to the reactive filter 108. In this regard, the auditory conduction pathways 202A-202I introduce air and / or radiation impedance to the transducer 124 that amplifies or enhances the frequency waves 120 output by the transducer 124 and, in turn, amplifies or enhances the audio waves generated from the ultrasonic frequencies using air nonlinearity as previously discussed. Typically, the auditory conduction pathways 202A-202I can increase the air or radiation impedance to amplify the ultrasonic frequencies 120 output by the transducer 124, which in turn amplifies or enhances the audio frequencies or sound waves output by the transducer, thus improving the efficiency.

[0022] As can be seen from Figure 3Further in the illustrated magnified perspective cutaway view of the representative auditory conduction pathway 202A of the filter 130, it can be seen that, in some aspects, the neck portions 204, 208 and the acoustic cavity 206 can have a cylindrical cross-sectional geometry. Further, the neck portion 204 is connected to and open to the output port 125 of the transducer 124, and the neck portion 208 is connected to and open to the attenuator 108. The acoustic cavity 206 is positioned between the neck portion 204 and the neck portion 208, such that each of the neck portions 204, 208 extends from opposite sides of the acoustic cavity 206. In some aspects, the neck portions 204, 208 can extend from a center of the acoustic cavity 206 and can be axially aligned with each other. The acoustic cavity 206 can have a cross-sectional dimension D2 that is wider than a cross-sectional dimension Dl of the neck portions 204, 208. For example, the cross-sectional dimension D2 can be at least twice Dl, or at least three times Dl. Further, it can be appreciated that, although the neck portions 204, 208 are shown as having the same cross-sectional dimension Dl, in some aspects they can have different cross-sectional dimensions. From Figure 3 It can be further seen from

[0023] Reference is now made to Figure 4 , Figure 4 A block diagram illustrating one aspect of an electronic device in which the previously discussed speaker can be implemented is shown. As shown in Figure 4 Device 400 can include a storage 402. Storage 402 can include one or more different types of storage, such as a hard disk drive storage, a non-volatile memory (e.g., a flash memory or other electrically programmable read only memory), a volatile memory (e.g., a battery-based static or dynamic random access memory), etc.

[0024] The processing circuit 404 can be used to control the operation of the device 400. The processing circuit 404 can be based on a processor, such as a microprocessor and other suitable integrated circuits. In one suitable arrangement, the processing circuit 404 and the storage device 402 can be used to run software on the device 400, such as an internet browsing application, an internet protocol voice (VOIP) telephone call application, an email application, a media playback application, operating system functions, and the like. The processing circuit 404 and the storage device 402 can be used to implement suitable communication protocols. Communication protocols that can be implemented using the processing circuit 404 and the storage device 402 include internet protocol, wireless local area network protocols (e.g., IEEE 802.11 protocols - sometimes referred to as Wi-Fi ® ), protocols for other short range wireless communication links such as Bluetooth ® protocols, protocols for handling 3G or 4G communication services (e.g., using wideband code division multiple access techniques), 2G cellular telephone communication protocols, and the like.

[0025] To minimize power consumption, the processing circuit 404 can include power management circuitry for implementing power management functionality. For example, the processing circuit 404 can be used to adjust the gain settings of amplifiers (e.g., radio frequency power amplifier circuitry) on the device 400. The processing circuit 404 can also be used to adjust the supply voltage provided to portions of the circuitry on the device 400. For example, more active circuitry can be provided with a higher direct current (DC) supply voltage, and less active or inactive circuitry can be provided with a lower DC supply voltage. If desired, the processing circuit 404 can be used to implement a control scheme in which the power amplifier circuitry is adjusted to accommodate transmission power level requests received from a wireless network.

[0026] The input output devices 406 can be used to allow data to be supplied to and provided from the device 400 to external devices. Display screens, microphone acoustic ports, speaker acoustic ports, and docking ports are examples of input output devices 406. For example, the input output devices 406 can include user input output devices 408, such as buttons, touch screens, joysticks, click wheels, scroll wheels, touch pads, keypads, keyboards, microphones, cameras, and the like. A user can provide commands to control the operation of the device 400 through the user input devices 408. The display and audio devices 410 can include liquid crystal display (LCD) screens or other screens, light emitting diode (LED) and other components that present visual information and status data. The display and audio devices 410 can also include audio equipment, such as speakers and other devices for producing sound. The display and audio devices 410 can include audio video interface equipment, such as jacks and other connectors for external headphones and monitors.

[0027] The wireless communication device 412 can include communication circuitry, such as radio frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, passive RF components, antennas, and other circuitry for handling RF wireless signals. Wireless signals can also be communicated using light (e.g., using infrared communication). Representatively, in the case of a speaker acoustic port, a speaker can be associated with the port and in communication with the RF antenna for transmitting signals from a remote user to the speaker.

[0028] Returning to FIG. 4, Figure 4 The device 400 can communicate with external devices such as accessories 414, computing equipment 416, and wireless networks 418, as represented by paths 420 and 422. The paths 420 can include wired paths and wireless paths. The paths 422 can be wireless paths. The accessories 414 can include headphones (e.g., wireless cellular headsets or audio headphones) and audio video equipment (e.g., wireless speakers, game controllers, or other equipment that receives and plays audio and video content), peripherals such as wireless printers or cameras, and the like.

[0029] The computing equipment 416 can be any suitable computer. In one suitable arrangement, the computing equipment 416 is a computer with an associated wireless access point (router) or internal or external wireless network card that establishes a wireless connection with the device 400. The computer can be a server (e.g., an Internet server), a local area network computer with or without Internet access, a user's own personal computer, a peer device (e.g., another portable electronic device), or any other suitable computing equipment.

[0030] The wireless networks 418 can include any suitable network equipment, such as cellular telephone base stations, cellular towers, wireless data networks, computers associated with the wireless networks, and the like. For example, the wireless networks 418 can include network management equipment that monitors the wireless signal strength of wireless handsets (cellular telephones, handheld computing devices, etc.) that are in communication with the networks 418.

[0031] While certain aspects have been described and shown in the drawings, it is to be understood that these aspects are merely exemplary of the broad disclosure and are not to be limiting and that the scope of the disclosure is not to be determined by the specific teachings contained therein, but only by the plain meaning of the claims. Accordingly, the description is to be regarded as illustrative in nature, and not restrictive. For example, while a speaker is specifically disclosed herein, the attenuators disclosed herein can be used with other types of transducers (e.g., microphones). Moreover, while a general portable electronic device is described herein, any of the previously discussed attenuator and transducer configurations can be implemented in devices such as wearable devices, earbuds, earphones, mobile communication devices, tablet computers, personal computers, laptop computers, notebook computers, etc. Furthermore, to aid the Patent Office and any readers of this application, the Applicant hereby states that they do not intend any of the appended claims to invoke 35 U.S.C. 112(f) unless the words "means for" or "step for" are explicitly used in the particular claim.

Claims

1. A reactance filter assembly comprising: a reactance filter acoustically coupled to a transducer operable to generate an audio frequency by air non-linear demodulation of an ultrasonic frequency, the reactance filter having a plurality of auditory conduction pathways tuned to introduce a radiation impedance to the transducer to improve transducer efficiency.

2. The reactance filter assembly of claim 1, wherein the reactance filter increases the radiation impedance to the transducer to improve the transducer efficiency.

3. The reactance filter assembly of claim 1, wherein the radiation impedance causes an amplified ultrasonic frequency output that brings a gain in an audio frequency output.

4. The reactance filter assembly of claim 1, wherein the reactance filter comprises a low pass filter.

5. The reactance filter assembly of claim 1, wherein each of the plurality of auditory conduction pathways comprises an acoustic cavity, a second neck, and a first neck coupling the acoustic cavity to the transducer.

6. The reactance filter assembly of claim 5, wherein a cross-sectional dimension of the acoustic cavity is greater than a cross-sectional dimension of the first neck or the second neck.

7. The reactance filter assembly of claim 5, wherein the first neck and the second neck have a same cross-sectional dimension, and the acoustic cavity has a cross-sectional dimension that is greater than the cross-sectional dimension of the first neck and the second neck.

8. The reactance filter assembly of claim 5, wherein the second neck couples the acoustic cavity to an attenuator configured to attenuate the ultrasonic frequency output by the transducer with the audio frequency.

9. A transducer assembly comprising: a transducer operable to generate an audio frequency by air non-linear demodulation of an ultrasonic frequency; and a reactance filter assembly coupled to the transducer and having an auditory conduction pathway comprising a first cross-sectional dimension and a second cross-sectional dimension, the auditory conduction pathway tuned to introduce a radiation impedance to the transducer to improve transducer efficiency.

10. The transducer assembly of claim 9, wherein the reactance filter assembly increases the radiation impedance to the transducer to improve the transducer efficiency.

11. The transducer assembly of claim 9, wherein the radiation impedance causes an amplified ultrasonic frequency output that brings a gain in an audio frequency output.

12. The transducer assembly of claim 9, wherein the first cross-sectional dimension defines an acoustic cavity, and the second cross-sectional dimension defines a second neck and a first neck coupling the acoustic cavity to the transducer.

13. The transducer assembly of claim 12, wherein the first cross-sectional dimension of the acoustic cavity is greater than the second cross-sectional dimension of the first neck and the second neck, and the second neck couples the acoustic cavity to an attenuator configured to attenuate the ultrasonic frequency output by the transducer with the audio frequency.

14. The transducer assembly of claim 9, wherein the auditory conduction pathway is a first auditory conduction pathway, and the reactance filter assembly includes a second auditory conduction pathway.

15. The transducer assembly of claim 9, wherein the transducer includes a microelectromechanical system speaker.

16. A portable electronic device, the portable electronic device comprising: a device housing having a housing wall defining an interior chamber separate from a surrounding environment; a transducer positioned within the interior chamber and operable to generate an audio frequency by air non-linear demodulation of an ultrasonic frequency; and a reactance filter assembly coupled to the transducer and having a plurality of auditory conduction pathways tuned to introduce a radiation impedance to the transducer to improve transducer efficiency.

17. The portable electronic device of claim 16, wherein the reactance filter assembly increases the radiation impedance to the transducer, and the radiation impedance causes an amplified ultrasonic frequency output that brings a gain in an audio frequency output.

18. The portable electronic device of claim 16, wherein the reactance filter assembly includes a low pass filter.

19. The portable electronic device of claim 16, wherein each of the plurality of auditory conduction pathways includes an acoustic cavity, a first neck coupling the acoustic cavity to the transducer, and a second neck coupling the acoustic cavity to an attenuator configured to attenuate the ultrasonic frequency output by the transducer with the audio frequency.

20. The portable electronic device of claim 19, wherein a cross-sectional dimension of the acoustic cavity is greater than a cross-sectional dimension of the first neck and the second neck.

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