Audio apparatus with integrated biometric signal acquisition

Abstract

An audio apparatus is provided, comprising at least one transducer for converting a first electrical signal into an audio signal; an electrically conductive path for conducting, via a switching network, (i) the first electrical signal to the at least one transducer and (ii) a second electrical signal to a sampling capacitor; the switching network comprising at least one first switch to couple the transducer to the path and at least one second switch to couple the sampling capacitor to the path; control circuitry configured to actuate the switching such that, during a first interval, the transducer is decoupled and the sampling capacitor is coupled to charge with the second signal, and during a second interval, the transducer is coupled to conduct the first signal; and measurement circuitry for generating, during the second interval and from charge held by the sampling capacitor, a measurement signal indicative of a biometric parameter.

Description

[0001] AUDIO APPARATUS WITH INTEGRATED BIOMETRIC SIGNAL ACQUISITION

[0002] CROSS-REFERENCE

[0003]

[0001] The present application claims priority on provisional U.S. Patent Application No. 63 / 702,005, entitled “SWITCHING SYSTEM AND METHOD FOR SIGNAL EXTRACTION USING STEREO HEADPHONES”, filed on October 1, 2024, the disclosure of which is incorporated by reference herein in their entirety.

[0004] FIELD

[0005]

[0002] The present technology is generally related to audio devices, and more specifically, to an apparatus for integrating audio playback with biometric signal acquisition.

[0006] BACKGROUND

[0007]

[0003] In recent years, audio apparatus such as headphones, earbuds, and headsets have become increasingly common for entertainment, communication, and professional use. In parallel, there has been growing interest in incorporating biometric signal acquisition into audio apparatus, allowing an audio apparatus to support both audio playback and biometric signal acquisition. Such biometric signal acquisition may include capturing signals associated with cardiac activity, respiration, or other physiological processes.

[0008]

[0004] Conventional audio apparatus with biometric signal acquisition capability may comprise one or more transducers driven by electrical signals delivered through electrically conductive paths. Biometric signal acquisition is commonly implemented using dedicated sensors, such as optical photoplethysmography (PPG) sensors, electrodes for electrocardiography (ECG), or dedicated accelerometers for mechanical sensing. In conventional audio apparatus, implementing both the functionalities of biometric signal acquisition and audio playback may require additional signal paths, additional sensors, and additional signal processing hardware, which may increase the size, cost, and complexity of an audio apparatus. The additional sensors may draw power independently of the audio path and may reduce the operating time of the apparatus. Furthermore, integrating additional sensors for biometric signal acquisition within the circuit of the apparatus may affect audio signal quality.

[0009]

[0005] In light of these considerations, at least some techniques have been developed to address challenges associated with integrating biometric signal acquisition into an audio apparatus. For example, European Patent No. EP1194007B1 discloses a method for converting signals in two- channel stereo format to become suitable to be played back using headphones. The invention also relates to a signal processing device for carrying out said method. According to the invention left direct path and left cross-talk path signals are formed from the left input signal, and correspondingly right direct path and right cross-talk path signals are formed from the right input signal, and further the left output signal is formed by combining said left direct-path and said right cross-talk path signals, and correspondingly, the right output signal is formed by combining said right direct-path and said left cross-talk path signals. The direct path signal each are formed using filtering associated with first frequency dependent gain and the cross-talk path signals each are formed using filtering associated with second frequency dependent gain and by adding interaural time difference.

[0010]

[0006] In another example, Canadian Patent No. CA3175775A1 discloses systems, methods, architectures, mechanisms and apparatus providing a sensing platform wherein one or more headphone drivers are used as a versatile sensor to receive excitation signals therefrom indicative of direct or indirect pressures associated with the ear canal acoustically cooperating with the diaphragms operatively coupled to the drivers.

[0011]

[0007] However, none of these conventional techniques are capable of providing an integrated audio playback apparatus that processes the extraction of biometric information without the use of external sensors.

[0012] SUMMARY

[0013]

[0008] Developers have devised methods and devices for overcoming at least some drawbacks present in prior art solutions.

[0009] Developers have designed a technology that may support integrated audio playback and biometric signal acquisition in an audio apparatus. More particularly, developers have designed an audio apparatus that comprises at least one transducer and an electrically conductive path incorporating a switching network. The switching network is configured to operate in alternating intervals: in one interval, the switching network couples the path to a transducer to deliver a first electrical signal for audio playback, and in another interval, the switching network couples a sampling capacitor to a node of the path to acquire a second electrical signal associated with at least one biometric parameter of the user of the apparatus. In the context of the present specification, the a second electrical signal may be referred to as the biometric signal. The audio apparatus further comprises a control circuitry configured to actuate the intervals in such a way that they are mutually exclusive. The audio apparatus further comprises a measurement circuitry configured to generate, from the charge held by the sampling capacitor, a measurement signal indicative of the biometric parameter.

[0014]

[0010] Embodiments of the present technology may have a variety of advantages. For example, some embodiments may reduce the number of signal paths by acquiring the biometric signal from nodes of an electrically conductive path already present in an audio apparatus. Additionally, by operating the switching network in alternating intervals at frequencies higher than the human audible range of approximately 20 Hz to 20 kHz, some embodiments of the present technology may allow biometric signals to be acquired without interrupting the audio playback. Additionally, some embodiments may reduce the size, cost, and complexity of the audio apparatus by avoiding dedicated biometric sensors and signal paths. Furthermore, some embodiments may reduce the power consumption of the apparatus by avoiding dedicated biometric sensors. Some embodiments may improve audio signal quality by reducing interference between audio signals and biometric signals.

[0015]

[0011] Some embodiments of the present technology can be used by manufacturers of headphones, earbuds, headsets, or other wearable audio apparatus to provide integrated biometric monitoring functions in addition to simultaneous audio playback.

[0016]

[0012] In a first broad aspect of the present technology, there is provided an audio apparatus, comprising: at least one transducer configured to convert a first electrical signal into an audio signal; an electrically conductive path configured to conduct, via a switching network, (i) the first electrical signal to the at least one transducer, and (ii) a second electrical signal to a sampling capacitor, the switching network comprising: at least one first switch configured to selectively couple the at least one transducer to the electrically conductive path; at least one second switch configured to selectively couple the sampling capacitor to the electrically conductive path; a control circuitry configured to actuate the switching network, the actuating the switching network comprising: during a first interval of time, decoupling the at least one transducer from the electrically conductive path and coupling the sampling capacitor to the electrically conductive path, to charge the sampling capacitor with the second electrical signal; during a second interval of time, coupling the at least one transducer to the electrically conductive path and decoupling the sampling capacitor from the electrically conductive path, to conduct the first electrical signal to the at least one transducer; and a measurement circuitry coupled to the sampling capacitor and configured to generate, during the second interval and from charge held by the sampling capacitor, a measurement signal indicative of a biometric parameter associated with a user of the audio apparatus.

[0017]

[0013] It is contemplated that such embodiments may reduce the number of signal paths by acquiring the biometric signal from nodes of an electrically conductive path already present in an audio apparatus. Additionally, such embodiments may reduce the size, cost, and complexity of the audio apparatus by avoiding dedicated biometric sensors and signal paths. Furthermore, such embodiments may reduce the power consumption of the apparatus by avoiding dedicated biometric sensors.

[0018]

[0014] In some embodiments of the audio apparatus, the electrically conductive path further comprises a coupling capacitor disposed in series with the at least one first switch.

[0019]

[0015] It is contemplated that such embodiments may support direct-current (DC) blocking along the electrically conductive path and may reduce distortion in audio playback.

[0020]

[0016] In some embodiments of the audio apparatus, the control circuitry is further configured to control the at least one first switch and the at least one second switch in an alternating manner, such that the first interval and the second interval are mutually exclusive.

[0017] It is contemplated that such embodiments may reduce interference between audio playback and acquisition of the biometric signal.

[0021]

[0018] In some embodiments of the audio apparatus, the sampling capacitor is configured to retain charge for a duration extending through the second interval.

[0022]

[0019] In some embodiments of the audio apparatus, the control circuitry comprises a signal generator configured to produce control signals to alternately actuate the at least one first switch and the at least one second switch.

[0023]

[0020] In some embodiments of the audio apparatus, the measurement circuitry comprises an analog-to-digital converter configured to digitize the measurement signal.

[0024]

[0021] It is contemplated that such embodiments may support digital processing of the biometric parameter within the audio apparatus.

[0025]

[0022] In some embodiments of the audio apparatus, the sampling capacitor is implemented as part of a sampling and anti-aliasing filter.

[0026]

[0023] In some embodiments of the audio apparatus, the biometric parameter is indicative of at least a heart-rate of the user.

[0027]

[0024] It is contemplated that such embodiments may support heart-rate monitoring using audio apparatus.

[0028]

[0025] In some embodiments of the audio apparatus, the first electrical signal is indicative of a monophonic sound.

[0029]

[0026] In some embodiments of the audio apparatus, the first electrical signal is indicative of a stereophonic sound.

[0030]

[0027] In some embodiments of the audio apparatus, the audio apparatus further comprises: an other transducer, the other transducer configured to convert an other electrical signal into an other audio signal; an other first switch, the other first switch configured to selectively couple the other transducer to the electrically conductive path; a differential amplifier configured to generate an output signal indicative of a difference between the first electrical signal and the other electrical signal, the output signal utilized by the measurement circuitry to generate the measurement signal.

[0031]

[0028] It is contemplated that the differential amplifier in such embodiments may reduce the common-mode components of the first electrical signal and the other electrical signal, and therefore may reduce interference between the first and the second electrical signals.

[0032]

[0029] In some embodiments of the audio apparatus, the first electrical signal and the other electrical signal correspond to a same electrical source.

[0033]

[0030] In some embodiments of the audio apparatus, the first electrical signal corresponds to a first electrical source and the other electrical signal corresponds to an other electrical source.

[0034]

[0031] In some embodiments of the audio apparatus, the at least one first switch and the other first switch are implemented as single-pole single-throw (SPST) switches to form an alternating-current (AC) bridge.

[0035]

[0032] In some embodiments of the audio apparatus, the at least one second switch is disposed at an input of the differential amplifier.

[0036]

[0033] In some embodiments of the audio apparatus, the at least one second switch is disposed at an output of the differential amplifier.

[0037]

[0034] In some embodiments of the audio apparatus, the audio apparatus further comprises an inverting amplifier disposed between the at least one first switch and the at least one second switch, the inverting amplifier comprising a feedback loop comprising a gain-control switch, the gaincontrol switch configured to vary a feedback resistance, to control a gain of the inverting amplifier.

[0038]

[0035] It is contemplated that such embodiments may provide adjustable gain to accommodate different magnitudes of the second electrical signal.

[0039]

[0036] In some embodiments of the audio apparatus, the audio apparatus further comprises a discharge switch coupled to a node of the electrically conductive path and configured to selectively discharge the coupling capacitor.

[0037] It is contemplated that such embodiments may reduce residual charge on the coupling capacitor that could otherwise influence acquisition of the second electrical signal.

[0040]

[0038] In the present disclosure, the terms “a” or “an” are defined to mean “at least one”, that is, these terms do not exclude a plural number of items, unless stated otherwise.

[0041]

[0039] In the present disclosure, terms such as “substantially”, “generally” and “about”, which modify a value, condition or characteristic of a feature of an example embodiment, should be understood to mean that the value, condition or characteristic is defined within tolerances that are acceptable for the proper operation of the example embodiment for its intended application.

[0042]

[0040] In the present disclosure, unless stated otherwise, the terms “connected” and “coupled”, and derivatives and variants thereof, refer herein to any structural or functional connection or coupling, either direct or indirect, between two or more elements. For example, the connection or coupling between the elements can be acoustical, mechanical, optical, electrical, thermal, logical, or any combinations thereof.

[0043]

[0041] In the present disclosure, expressions such as “match”, “matching” and “matched”, including variants and derivatives thereof, are intended to refer herein to a condition in which two or more elements are either the same or within some predetermined tolerance of each other. That is, these terms are meant to encompass not only “exactly” or “identically” matching the two elements but also “substantially”, “approximately” or “subjectively” matching the two or more elements, as well as providing a higher or best match among a plurality of matching possibilities.

[0044]

[0042] In the present disclosure, the expression “based on” is intended to mean “based at least partly on”, that is, this expression can mean “based solely on” or “based partially on”, and so should not be interpreted in a limited manner. More particularly, the expression “based on” could also be understood as meaning “depending on”, “representative of’, “indicative of’, “associated with” or similar expressions.

[0045]

[0043] In the present disclosure, "At least one" means one or more, and "a plurality of' means two or more. The term "and / or" describes an association relationship of associated objects, and indicates that three relationships may exist. For example, A and / or B may indicate the following three cases: Only A exists, both A and B exist, and only B exists, where A and B may be singular or plural. The character indicates an "or" relationship between associated objects. "At least one of the following items (pieces)" or a similar expression thereof indicates any combination of these items, including a single item (piece) or any combination of a plurality of items (pieces). For example, "at least one of A, B, or C" includes: only A; only B; only C; A and B; A and C; B and C; or A, B, and C, and "at least one of A, B, and C" may also be understood as including: only A; only B; only C; A and B; A and C; B and C; or A, B, and C. In addition, unless otherwise specified, ordinal numbers such as "first" and "second" in implementations of this application are used to distinguish between a plurality of objects, and are not used to limit a sequence, a time sequence, priorities, or importance of the plurality of objects.

[0046]

[0044] A person skilled in the art should understand that implementations described herein may be provided as a method, an apparatus (or system), computer-readable storage medium, or a computer program product. Therefore, the embodiments described herein may be a hardware-only embodiment, a software-only embodiment, or an embodiment with a combination of software and hardware. Moreover, these embodiments may be in the form of a computer program product that is implemented on one or more computer-usable storage media (including but not limited to a disk memory, an optical memory, and the like) that include computer-usable program code.

[0047]

[0045] It should be understood that computer program instructions may be used to implement operations of control circuitry and measurement circuitry described in the present disclosure, including generation of control signals for actuating the switching network in alternating intervals and processing of signals derived from the sampling capacitor. The computer program instructions may be provided to a general-purpose or dedicated controller, an embedded processor, or another programmable data-processing device and, when executed, may cause the apparatus to perform functions described herein.

[0048]

[0046] The computer program instructions may alternatively be loaded onto a computer or another programmable data processing device, so that a series of operations and steps are performed on the computer or the programmable device to actuate the switching network and to process a measurement signal, thereby providing computer-implemented processing consistent with the procedures described in the present disclosure.

[0047] A person skilled in the art can make various modifications and variations to this application without departing from the scope of this disclosure. This disclosure is intended to cover these modifications and variations of this application provided that they fall within the scope of protection defined by the following claims and their equivalent technologies.

[0049] BRIEF DESCRIPTION OF THE DRAWINGS

[0050]

[0048] For a better understanding of the present technology, as well as other aspects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where:

[0051]

[0049] FIG. 1 illustrates a control circuitry communicatively coupled to a switching network in an audio apparatus, in accordance with various embodiments of the present technology.

[0052]

[0050] FIG. 2 illustrates a measurement circuitry communicatively coupled to a sampling capacitor in an audio apparatus, in accordance with various embodiments of the present technology.

[0053]

[0051] FIG. 3 illustrates an audio apparatus for audio playback and biometric signal acquisition, in accordance with at least some non-limiting embodiments of the present technology.

[0054]

[0052] FIG. 4 illustrates an audio apparatus for playback of monophonic sound and biometric signal acquisition, in accordance with at least some non-limiting implementations of the present technology.

[0055]

[0053] FIG. 5 illustrates an audio apparatus for playback of pseudo-stereophonic sound and biometric signal acquisition, in accordance with at least some non-limiting implementations of the present technology.

[0056]

[0054] FIG. 6 illustrates an audio apparatus for playback of stereophonic sound and biometric signal acquisition, in accordance with at least some non-limiting implementations of the present technology.

[0055] FIG. 7 illustrates an audio apparatus for playback of monophonic sound and biometric signal acquisition, in accordance with at least some non-limiting implementations of the present technology.

[0057]

[0056] FIG. 8 illustrates an audio apparatus for playback of pseudo-stereophonic sound and biometric signal acquisition, in accordance with at least some non-limiting implementations of the present technology.

[0058]

[0057] FIG. 9 illustrates an audio apparatus for playback of stereophonic sound and biometric signal acquisition, in accordance with at least some non-limiting implementations of the present technology.

[0059]

[0058] FIG. 10 illustrates an audio apparatus for audio playback and biometric signal acquisition, in accordance with at least some non-limiting embodiments of the present technology.

[0060]

[0059] FIG. 11 illustrates an audio apparatus comprising a switched capacitor network for audio playback and biometric signal acquisition, in accordance with at least some non-limiting embodiments of the present technology.

[0061]

[0060] FIG. 12 illustrates an equivalent circuit 1200 of an audio apparatus for audio playback and biometric signal acquisition, in accordance with at least some non-limiting embodiments of the present technology.

[0062]

[0061] It should be noted that, unless otherwise explicitly specified herein, the drawings are not to scale.

[0063] DETAILED DESCRIPTION

[0064]

[0062] The examples and conditional language recited herein are principally intended to aid the reader in understanding the principles of the present technology and not to limit its scope to such specifically recited examples and conditions. It will be appreciated that those skilled in the art may devise various arrangements which, although not explicitly described or shown herein, nonetheless embody the principles of the present technology and are included within its spirit and scope.

[0063] Furthermore, as an aid to understanding, the following description may describe relatively simplified implementations of the present technology. As persons skilled in the art would understand, various implementations of the present technology may be of a greater complexity.

[0065]

[0064] In some cases, what are believed to be helpful examples of modifications to the present technology may also be set forth. This is done merely as an aid to understanding, and, again, not to define the scope or set forth the bounds of the present technology. These modifications are not an exhaustive list, and a person skilled in the art may make other modifications while nonetheless remaining within the scope of the present technology. Further, where no examples of modifications have been set forth, it should not be interpreted that no modifications are possible and / or that what is described is the sole manner of implementing that element of the present technology.

[0066]

[0065] Moreover, all statements herein reciting principles, aspects, and implementations of the present technology, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof, whether they are currently known or developed in the future. Thus, for example, it will be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative circuitry embodying the principles of the present technology. Similarly, it will be appreciated that any flowcharts, flow diagrams, state transition diagrams, pseudo-code, and the like represent various processes which may be substantially represented in computer-readable media and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.

[0067]

[0066] The functions of the various elements shown in the figures, including any functional block labeled as a "processor", may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. In some implementations of the present technology, the processor may be a general purpose processor, such as a central processing unit (CPU) or a processor dedicated to a specific purpose, such as a digital signal processor (DSP). Moreover, explicit use of the term a "processor" should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, application specific integrated circuit (ASIC), field programmable gate array (FPGA), read-only memory (ROM) for storing software, random access memory (RAM), and non-volatile storage. Other hardware, conventional and / or custom, may also be included.

[0068]

[0067] Software modules, or simply modules which are implied to be software, may be represented herein as any combination of flowchart elements or other elements indicating performance of process steps and / or textual description. Such modules may be executed by hardware that is expressly or implicitly shown. Moreover, it should be understood that module may include for example, but without being limitative, computer program logic, computer program instructions, software, stack, firmware, hardware circuitry or a combination thereof which provides the required capabilities.

[0069]

[0068] With these fundamentals in place, we will now consider some non-limiting examples to illustrate various implementations of aspects of the present technology. Generally speaking, the embodiments of the present technology, as disclosed below are directed to an integrated audio playback apparatus and associated methods capable of processing the extraction of biometric information without the use of external sensors.

[0070]

[0069] FIG. 1 illustrates a control circuitry 100 communicatively coupled to a switching network 160 in an audio apparatus, in accordance with various embodiments of the present technology. In the context of the present specification, an audio apparatus may refer to any device comprising at least one transducer configured to convert an electrical signal into an audio signal, such as headphones, earbuds, headsets etc. (collectively referred to hereinafter as “headphones” for conciseness).

[0071]

[0070] The control circuitry 100 may comprise an oscillator 110, a signal generator 120, a microcontroller 130, and switch drivers 140. The control circuitry 100 may be configured to generate a control signal 150 for actuating the switching network 160.

[0072]

[0071] The oscillator 110 may provide a timing reference to the signal generator 120 and to the microcontroller 130. The signal generator 120 may generate phase signals based on the timing reference received from the oscillator 110. The phase signals generated by the signal generator 120 may define a first interval of time and a second interval of time in an alternating manner such that the first interval and the second interval are mutually exclusive. The microcontroller 130 may configure different properties of the phase signal generated by the signal generator 120, for example, frequency and / or duty cycle.

[0073]

[0072] Based on the phase signals generated by the signal generator 120, the switch drivers 140 may generate the control signal 150 to control the switches within the switching network 160.

[0074]

[0073] FIG. 2 illustrates a measurement circuitry 200 communicatively coupled to a sampling capacitor 260 in an audio apparatus, in accordance with various embodiments of the present technology. The measurement circuitry 200 may comprise a high-impedance buffer 210, a Programmable Gain Amplifier (PGA) 220, an Analog-to-Digital converter (ADC) 230, and a processor 240. The measurement circuitry 200 may be configured to process a measurement signal 250 generated from a charge held by the sampling capacitor 260.

[0075]

[0074] The high-impedance buffer 210 may be configured to receive the measurement signal 250 from the sampling capacitor 260 while reducing loading effects on the sampling capacitor 260. The PGA 220 may be configured to adjust the amplitude of the measurement signal 250. The ADC 230 may be configured to digitize the amplitude-adjusted measurement signal for further processing. The processor 240 may be configured to process the digitized measurement signal to extract information indicative of a biometric parameter associated with a user of the audio apparatus.

[0076]

[0075] FIG. 3 illustrates an audio apparatus 300 for audio playback and biometric signal acquisition, in accordance with at least some non-limiting embodiments of the present technology.

[0077]

[0076] The audio apparatus 300 may comprise an electrical source 310 associated with a first electrical signal, a first switch 350, a second switch 340, a transducer 325 configured to convert the first electrical signal into an audio signal, and an electrical source 320 associated with a second electrical signal corresponding to a biometric parameter of a user of the audio apparatus 300.

[0078]

[0077] The first electrical signal generated by the electrical source 310 may be connected in series with a coupling capacitor 330 and a first switch 350. The first switch 350 may be part of the switching network 160 described previously with reference to FIG. 1. The first switch 350 may be actuated by the control circuitry 100 (described previously with reference to FIG. 1) based on the control signal 150. The first switch 350 and the second switch 340 are actuated in an alternating manner such that when the first switch 350 is open, the second switch 340 is closed, and vice- versa. When the first switch 350 is closed, the first electrical signal from the source 310 is conducted to the transducer 325 via the coupling capacitor 330. The transducer 325 converts the first electrical signal to audio signal for playback. The coupling capacitor 330 may provide direct- current (DC) blocking for the first electrical signal conducted to the transducers 325, thereby enhancing the quality of the first electrical signal conducted to the transducer 325.

[0079]

[0078] The second electrical signal generated by the electrical source 320 may correspond to a biometric signal such as the heart-rate of the user of the apparatus 300. In some embodiments, the electrical source 320 may correspond to an electrode positioned in an ear of the user, and the biometric parameter may be related to cardiac activity, for example, the heart-rate of the user. The second electrical signal may be conducted to the sampling capacitor 260 through a second switch 340. The second switch 340 may be part of the switching network 160 described previously with reference to FIG. 1. The second switch 340 may be actuated by the control circuitry 100 (described previously with reference to FIG. 1) based on the control signal 150. When the second switch 340 is closed, the sampling capacitor 260 gets coupled to the source 320 and gets charged with the second electrical signal generated by the electrical source 320. When the sampling capacitor 260 gets charged upto a predefined maximum threshold, the control circuitry 100 may open the second switch 340 (and close the first switch 350), decoupling the sampling capacitor 260 from the source 320. Once decoupled, the sampling capacitor begins to discharge, generating the measurement signal 250. The measurement circuitry 200 may receive the measurement signal 250 through its high-impedance buffer 210 and extract information indicative of a biometric parameter associated with a user of the audio apparatus 300, as described previously with reference to FIG. 2.

[0080]

[0079] Once the sampling capacitor 260 is discharged to a predefined minimum threshold, the control circuitry 100 may again close the second switch 340 (and open the first switch 350). In this manner, the control circuitry 100 may alternately actuate the first switch 350 and the second switch 340 in successive intervals, thereby supporting audio playback through the transducer 325 and acquisition of the biometric signal through the sampling capacitor 260 and measurement circuitry 200. In some embodiments, the control circuitry 100 may configure the actuation frequency of the switches 340, 350 to be higher than the human audible range of approximately 20 Hz to 20 kHz, such that the alternating switching operation does not cause any perceptible interruption in audio playback for the user.

[0081]

[0080] The electrical interconnections between different components of the apparatus 300, such as the electrical sources 310 and 320, the coupling capacitor 330, the first switch 350, the second switch 340, the transducer 325, the sampling capacitor 260, the measurement circuitry 200, and the control circuitry 100, may collectively be referred to as the electrically conductive path.

[0082]

[0081] FIG. 4 illustrates an audio apparatus 400 for playback of monophonic sound and biometric signal acquisition, in accordance with at least some non-limiting implementations of the present technology. In the context of the present specification, monophonic sound may refer to the playback of a single audio channel that is delivered identically to both ears of a user.

[0083]

[0082] The apparatus 400 may comprise an electrical source 405 associated with an electrical signal indicative of a monophonic sound, electrical sources 425 and 440 associated with electrical signals indicative of a biometric parameter, coupling capacitors 410 and 430, switches 415, 435 and 465, transducers 420 and 445, a differential amplifier 460 with input nodes 450 and 455, and a sampling and anti-aliasing filter 470 coupled to the measurement circuitry.

[0084]

[0083] The switches 415, 435, and 465 may be part of the switching network 160 depicted in FIG.

[0085] 1 and are controlled by the control circuitry 100 (depicted in FIG. 1). The timing waveforms 475 and 480 represent the control signals generated by the control circuitry 100 for the switches 415 / 435 and 465 respectively. It can be appreciated that the control signals 475 (for switches 415 / 435) and 480 (for switch 465) are non-overlapping and vary with time in an alternating manner. When the switches 415 and 435 are closed (and the switch 465 is open), the electrical signal from the source 405 passes through the coupling capacitors 410 and 430 to the transducers 420 and 445 respectively. The coupling capacitors 410 and 430 may provide direct- current (DC) blocking for the electrical signal conducted to the transducers 420 and 445, thereby enhancing the quality of the signal conducted to the transducers 420 and 445. The transducers 420 and 445 convert the electrical signal from the source 405 to audio signal, thereby generating audio playback output. During this time, the sources 425 and 440 are electrically isolated from the differential amplifier 460 because the switch 465 remains open, and therefore no biometric signal acquisition takes place.

[0086]

[0084] When the switch 465 is closed (and the switches 415 and 435 are open), the sources 425 and 440 become coupled to the differential amplifier 460. In some embodiments, the sources 425 and 440 may correspond to electrodes positioned on the left and right ears of the user, and the biometric parameter may be related to cardiac activity, for example, the heart-rate of the user. Because the heart is anatomically closer to the left side of the body, the signals detected at the two ears may share common components while also exhibiting differences related to the proximity of the heart. The differential amplifier 460 generates an output signal corresponding to the difference between the signals from the sources 425 and 440. In this way, the differential amplifier 460 may suppress the common-mode components while retaining the differential component attributable to the user’s heart activity. During the interval when the switches 415 and 435 remain open, the source 405 is isolated from the transducers 420 and 445, and therefore no audio playback takes place. However, in some embodiments, the interruption in playback may not be perceptible to the user, because the control circuitry 100 may actuate the switches 415, 435, and 465 at a frequency higher than the human audible range of approximately 20 Hz to 20 kHz.

[0087]

[0085] The output signal from the differential amplifier 460 may be conducted to the sampling and anti-aliasing filter 470. In some embodiments, the filter 470 may comprise the sampling capacitor 260 described previously with reference to FIG. 2. The filter 470 may condition the output signal from the differential amplifier 460, for example, by limiting high-frequency components and retaining signal components relevant to the biometric parameter.

[0088]

[0086] Once the sampling capacitor 260 within the filter 470 is charged to a predefined maximum threshold, the control circuitry 100 may open the switch 465 (and close the switches 415 and 435), decoupling the differential amplifier 460 from the sources 425 and 440. The sampling capacitor 260 then begins to discharge, generating the measurement signal 250.

[0089]

[0087] The measurement circuitry 200, described previously with reference to FIG. 2, may process the measurement signal 250. For example, the high-impedance buffer 210 may reduce loading Y1 effects on the sampling capacitor 260, the programmable gain amplifier 220 may adjust the amplitude of the signal, and the analog-to-digital converter 230 may digitize the signal for processing by the processor 240. The processor 240 may extract information indicative of the biometric parameter, such as the heart-rate of the user.

[0090]

[0088] Once the sampling capacitor 260 discharges to a predefined minimum threshold, the control circuitry 100 may again close the switch 465 (and open the switches 415 and 435), repeating the alternating intervals between audio playback and biometric signal acquisition. In some embodiments, the frequency of alternation may be set higher than the audible range of approximately 20 Hz to 20 kHz, such that the user does not perceive any interruption in the audio playback.

[0091]

[0089] FIG. 5 illustrates an audio apparatus 500 for playback of pseudo-stereophonic sound and biometric signal acquisition, in accordance with at least some non-limiting implementations of the present technology. In the context of the present specification, pseudo-stereophonic sound may refer to an audio playback where two audio channels are played, but the channels originate from the same or substantially similar audio content.

[0092]

[0090] The apparatus 500 may comprise electrical sources 505 and 506 associated with electrical signals indicative of a pseudo-stereophonic audio playback, electrical sources 425 and 440 associated with electrical signals indicative of a biometric parameter, coupling capacitors 410 and 430, switches 415, 435 and 465, transducers 420 and 445, a differential amplifier 460 with input nodes 450 and 455, and a sampling and anti-aliasing filter 470 coupled to the measurement circuitry 200.

[0093]

[0091] As described previously with reference to FIG. 4, the switches 415, 435, and 465 may be part of the switching network 160 (described previously with reference to FIG. 1) and are actuated by the control circuitry 100. The timing waveforms 475 and 480 represent the control signals generated by the control circuitry 100 for switches 415 / 435 and 465 respectively. It can be appreciated that the control signals 475 and 480 are non-overlapping and alternate in time. When switches 415 and 435 are closed (and switch 465 is open), the electrical signals from the sources 505 and 506 are conducted through the coupling capacitors 410 and 430 to the transducers 420 and 445 respectively. The transducers 420 and 445 convert these signals into audio signals for playback, thereby producing a pseudo-stereophonic output. The coupling capacitors 410 and 430 may provide direct-current (DC) blocking for the conducted signals, thereby improving playback quality. During this interval, the sources 425 and 440 remain electrically isolated from the differential amplifier 460, and no biometric acquisition takes place.

[0094]

[0092] When the switch 465 is closed (and the switches 415 and 435 are open), the sources 425 and 440 are coupled to the differential amplifier 460. In some embodiments, the sources 425 and 440 may correspond to electrodes positioned on the left and right ears of the user, and the biometric parameter may be related to cardiac activity, such as the heart-rate of the user. Because the heart is anatomically closer to the left side of the body, the signals detected at the left and right ears may share common components while also exhibiting differential components attributable to heart activity. The differential amplifier 460 suppresses the common-mode components while retaining the differential components, thereby generating an output signal representative of the user’s heart activity.

[0095]

[0093] The output signal from the differential amplifier 460 may be provided to the sampling and anti-aliasing filter 470, which may include the sampling capacitor 260 described previously with reference to FIG. 2. The filter 470 may condition the output signal by attenuating high-frequency components and passing frequencies relevant to the biometric parameter. Once the sampling capacitor 260 charges to a predefined maximum threshold, the control circuitry 100 may open the switch 465 (and close the switches 415 and 435), decoupling the sources 425 and 440 from the differential amplifier 460. The sampling capacitor 260 then discharges, generating the measurement signal 250, which is processed by the measurement circuitry 200 as described previously with reference to FIG. 2.

[0096]

[0094] Once the sampling capacitor 260 discharges to a predefined minimum threshold, the control circuitry 100 may again close the switch 465 (and open the switches 415 and 435), repeating the alternating intervals between pseudo-stereophonic playback and biometric signal acquisition. In some embodiments, the actuation frequency of the switches 415, 435, and 465 may be higher than the human audible range of approximately 20 Hz to 20 kHz, such that no perceptible interruption occurs in the audio playback.

[0095] FIG. 6 illustrates an audio apparatus 600 for playback of stereophonic sound and biometric signal acquisition, in accordance with at least some non-limiting implementations of the present technology. In the context of the present specification, stereophonic sound may refer to an audio playback where two independent audio channels, typically designated as left and right, are played.

[0097]

[0096] The apparatus 600 may comprise electrical sources 605 and 606 associated with left and right audio channels, electrical sources 425 and 440 associated with a biometric signal, coupling capacitors 610 and 630, switches 465, 683, 684, 685, 686, transducers 420 and 445, amplifiers 681 and 682, variable impedances 688, 689, 687, and 690, a differential amplifier 460, and a sampling and anti-aliasing filter 470 coupled to the measurement circuitry 200.

[0098]

[0097] The switches 685, 686, 683, and 684 and the switch 465 may be part of the switching network 160 (FIG. 1) and are actuated by the control circuitry 100. The waveform 675 is the control signal that simultaneously actuates the switches 685, 686, 683, and 684. The waveform 680 actuates the switch 465. It can be appreciated that the waveforms 675 and 680 are nonoverlapping and alternate in time. The switches 683 and 684 represent a pair of Single-Pole-Single- Throw (SPST) switches and the switches 685 and 686 represent another pair of SPST switches.

[0099]

[0098] When the control signal 675 closes the switches 685, 686, 683, and 684 (and the control signal 680 maintains the switch 465 open), the electrical signals from the sources 605 and 606 are conducted through the coupling capacitors 610 and 630 to the amplifiers 681 and 682, and also to the transducers 420 and 445, respectively. The transducers 420 and 445 convert the electrical signals into corresponding audio signals, thereby providing stereophonic playback to the user. The coupling capacitors 610 and 630 may provide direct-current (DC) blocking, thereby enhancing the quality of the signals conducted to the transducers 420 and 445. During this interval, the sources 425 and 440 remain electrically isolated from the differential amplifier 460 because the switch 465 is open, and therefore no biometric signal acquisition occurs. Furthermore, during this interval, the amplifiers 681 and 682 and the variable impedances 688, 689, 687, and 690 remain electrically isolated from the transducers 420 and 445, and do not affect the audio playback.

[0100]

[0099] When the control signal 675 opens the switches 685, 686, 683, and 684 (and the control signal 680 closes the switch 465), the sources 425 and 440, which may correspond to electrodes positioned on the left and right ears of the user, are coupled into amplifier 681 via variable impedances 688 and 689 and into amplifier 682 via variable impedances 687 and 690. The amplifiers 681 and 682 together with their respective impedance pairs (impedances 688 and 689 for amplifier 681; impedances 687 and 690 for amplifier 682) form an AC bridge that can be tuned to adjust the effective transfer function of the transducers 420 and 445 in a specific frequency band of interest. Because the heart is anatomically closer to the left side of the body, the electrical signals detected at the two ears may share common components while also exhibiting differences attributable to cardiac activity. The differential amplifier 460 receives the outputs of amplifiers 681 and 682, suppresses common-mode interference, and retains the differential component that reflects the user’s heart activity. By leveraging the AC-bridge configuration and selective tuning of the effective transfer function of the transducers 420 and 445, the apparatus 600 may improve the signal-to-noise ratio (SNR) of the acquired biometric signals and reduce the mean bias absolute percentage error (MB APE) in the estimation of biometric parameters such as heart rate.

[0101]

[0100] The output signal from the differential amplifier 460 may be provided to the sampling and anti-aliasing filter 470, which may include the sampling capacitor 260 described previously with reference to FIG. 2. The filter 470 may condition the output signal by attenuating high-frequency components and passing frequencies relevant to the biometric parameter. Once the sampling capacitor 260 charges to a predefined maximum threshold, the control circuitry 100 may open the switch 465 (and close the switches 685, 686, 683, and 684), decoupling the sources 425 and 440 from the differential amplifier 460. The sampling capacitor 260 then discharges, generating the measurement signal 250, which is processed by the measurement circuitry 200 as described previously with reference to FIG. 2.

[0102]

[0101] Once the sampling capacitor 260 discharges to a predefined minimum threshold, the control circuitry 100 may again close the switch 465 (and open the switches 685, 686, 683, and 684), repeating the alternating intervals between stereophonic playback and biometric signal acquisition. In some embodiments, the actuation frequency of the switches 685, 686, 683, 684, and 465 may be higher than the human audible range of approximately 20 Hz to 20 kHz, such that no perceptible interruption occurs in the audio playback.

[0102] FIG. 7 illustrates an audio apparatus 700 for playback of monophonic sound and biometric signal acquisition, in accordance with at least some non-limiting implementations of the present technology. In the context of the present specification, monophonic sound may refer to the playback of a single audio channel that is delivered identically to both ears of a user.

[0103]

[0103] The apparatus 700 may comprise an electrical source 405 associated with an electrical signal indicative of a monophonic sound, electrical sources 425 and 440 associated with electrical signals indicative of a biometric parameter, coupling capacitors 410 and 430, switches 415, 435, 740, and 745, transducers 420 and 445, a differential amplifier 460, and a sampling and antialiasing filter 470 coupled to the measurement circuitry 200.

[0104]

[0104] The switches 415, 435, 740, and 745 may be part of the switching network 160 (FIG. 1) and are actuated by the control circuitry 100. The timing waveforms 775 and 780 represent the control signals generated by the control circuitry 100 for the switches 415, 435 and the switches 740, 745 respectively. It can be appreciated that the control signals 775 and 780 are nonoverlapping and alternate in time.

[0105]

[0105] When the switches 415 and 435 are closed (and the switches 740 and 745 remain open), the electrical signal from the source 405 passes through the coupling capacitors 410 and 430 to the transducers 420 and 445, respectively. The coupling capacitors 410 and 430 may provide direct- current (DC) blocking for the electrical signal conducted to the transducers 420 and 445, thereby enhancing playback quality. The transducers 420 and 445 convert the electrical signal from the source 405 into audio signals, thereby generating audio playback output. During this interval, the sources 425 and 440 remain electrically isolated from the differential amplifier 460 because the switches 740 and 745 are open, and therefore no biometric acquisition occurs.

[0106]

[0106] When the switches 740 and 745 are closed (and the switches 415 and 435 are open), the sources 425 and 440 are coupled to the differential amplifier 460. In some embodiments, the sources 425 and 440 may correspond to electrodes positioned on the left and right ears of the user, and the biometric parameter may be related to cardiac activity, for example, the heart-rate of the user. Because the heart is anatomically closer to the left side of the body, the signals detected at the two ears may share common components while also exhibiting differences attributable to heart activity. The differential amplifier 460 suppresses the common-mode components while retaining the differential component, thereby generating an output signal representative of the user’s heart activity. During this interval, the source 405 is isolated from the transducers 420 and 445 because the switches 415 and 435 are open, and therefore no audio playback occurs. However, in some embodiments, the interruption in playback may not be perceptible to the user, because the control circuitry 100 may actuate the switches 415, 435, 740, and 745 at a frequency higher than the human audible range of approximately 20 Hz to 20 kHz.

[0107]

[0107] It is contemplated that the provision of the switches 740 and 745 at the input of the differential amplifier 460 disconnects the sources 425 and 440 from the amplifier 460 during audio playback, thereby preventing noise leakage into the amplifier 460 and avoiding unnecessary power consumption.

[0108]

[0108] The output signal from the differential amplifier 460 may be provided to the sampling and anti-aliasing filter 470, which may include the sampling capacitor 260 described previously with reference to FIG. 2. The filter 470 may condition the output signal by attenuating high-frequency components and passing frequencies relevant to the biometric parameter. Once the sampling capacitor 260 charges to a predefined maximum threshold, the control circuitry 100 may open the switches 740 and 745 (and close the switches 415 and 435), decoupling the sources 425 and 440 from the differential amplifier 460. The sampling capacitor 260 then discharges, generating the measurement signal 250, which is processed by the measurement circuitry 200 as described previously with reference to FIG. 2.

[0109]

[0109] Once the sampling capacitor 260 discharges to a predefined minimum threshold, the control circuitry 100 may again close the switches 740 and 745 (and open the switches 415 and 435), repeating the alternating intervals between audio playback and biometric signal acquisition. In some embodiments, the actuation frequency of the switches 415, 435, 740, and 745 may be higher than the human audible range of approximately 20 Hz to 20 kHz, such that no perceptible interruption occurs in the audio playback.

[0110] FIG. 8 illustrates an audio apparatus 800 for playback of pseudo-stereophonic sound and biometric signal acquisition, in accordance with at least some non-limiting implementations of the present technology. In the context of the present specification, pseudo-stereophonic sound may refer to an audio playback where two audio channels are played, but the channels originate from the same or substantially similar audio content.

[0110]

[0111] The apparatus 800 may comprise electrical sources 505 and 506 associated with electrical signals indicative of a pseudo-stereo audio playback, electrical sources 425 and 440 associated with electrical signals indicative of a biometric parameter, coupling capacitors 410 and 430, switches 415, 435, 840, and 845, transducers 420 and 445, a differential amplifier 460, and a sampling and anti-aliasing filter 470 coupled to the measurement circuitry 200.

[0111]

[0112] The switches 415, 435, 840, and 845 may be part of the switching network 160 (FIG. 1) and are actuated by the control circuitry 100. The timing waveforms 875 and 880 represent the control signals generated by the control circuitry 100 for the switches 415 / 435 and the switches 840 / 845, respectively. It can be appreciated that the control signals 875 and 880 are nonoverlapping and alternate in time.

[0112]

[0113] When the switches 415 and 435 are closed (and the switches 840 and 845 remain open), the electrical signals from the sources 505 and 506 are conducted through the coupling capacitors 410 and 430 to the transducers 420 and 445, respectively. The transducers 420 and 445 convert these signals into audio signals for playback, thereby producing a pseudo-stereophonic output. The coupling capacitors 410 and 430 may provide direct-current (DC) blocking for the conducted signals, thereby improving playback quality. During this interval, the sources 425 and 440 remain electrically isolated from the differential amplifier 460 because the switches 840 and 845 are open, and therefore no biometric acquisition takes place.

[0113]

[0114] When the switches 840 and 845 are closed (and the switches 415 and 435 are open), the sources 425 and 440 are coupled to the differential amplifier 460. In some embodiments, the sources 425 and 440 may correspond to electrodes positioned on the left and right ears of the user, and the biometric parameter may be related to cardiac activity, such as the heart-rate of the user. Because the heart is anatomically closer to the left side of the body, the signals detected at the left and right ears may share common components while also exhibiting differential components attributable to heart activity. The differential amplifier 460 suppresses the common-mode components while retaining the differential components, thereby generating an output signal representative of the user’s heart activity. During this interval, the sources 505 and 506 are isolated from the transducers 420 and 445, and therefore no audio playback occurs. However, in some embodiments, the interruption in playback may not be perceptible to the user, because the control circuitry 100 may actuate the switches 415, 435, 840, and 845 at a frequency higher than the human audible range of approximately 20 Hz to 20 kHz.

[0114]

[0115] It is contemplated that the provision of the switches 840 and 845 at the input of the differential amplifier 460 disconnects the sources 425 and 440 from the amplifier 460 during audio playback, thereby preventing noise leakage into the amplifier 460 and avoiding unnecessary power consumption.

[0115]

[0116] The output signal from the differential amplifier 460 may be provided to the sampling and anti-aliasing filter 470, which may include the sampling capacitor 260 described previously with reference to FIG. 2. The filter 470 may condition the output signal by attenuating high-frequency components and passing frequencies relevant to the biometric parameter. Once the sampling capacitor 260 charges to a predefined maximum threshold, the control circuitry 100 may open the switches 840 and 845 (and close the switches 415 and 435), decoupling the sources 425 and 440 from the differential amplifier 460. The sampling capacitor 260 then discharges, generating the measurement signal 250, which is processed by the measurement circuitry 200 as described previously with reference to FIG. 2.

[0116]

[0117] Once the sampling capacitor 260 discharges to a predefined minimum threshold, the control circuitry 100 may again close the switches 840 and 845 (and open the switches 415 and 435), repeating the alternating intervals between pseudo-stereophonic playback and biometric signal acquisition. In some embodiments, the actuation frequency of the switches 415, 435, 840, and 845 may be higher than the human audible range of approximately 20 Hz to 20 kHz, such that no perceptible interruption occurs in the audio playback.

[0117]

[0118] FIG. 9 illustrates an audio apparatus 900 for playback of stereophonic sound and biometric signal acquisition, in accordance with at least some non-limiting implementations of the present technology. In the context of the present specification, stereophonic sound may refer to an audio playback where two independent audio channels, typically designated as left and right, are played.

[0118]

[0119] The apparatus 900 may comprise electrical sources 605 and 606 associated with left and right audio channels, electrical sources 425 and 440 associated with a biometric signal, coupling capacitors 610 and 630, switches 685, 686, 683, 684, 940, and 945, transducers 420 and 445, amplifiers 681 and 682, variable impedances 688, 689, 687, and 690, a differential amplifier 460, and a sampling and anti-aliasing filter 470 coupled to the measurement circuitry 200.

[0119]

[0120] The switches 685, 686, 683, and 684, together with switches 940 and 945, may be part of the switching network 160 (FIG. 1) and are actuated by the control circuitry 100. The timing waveform 975 represents the control signal that simultaneously actuates the switches 685, 686, 683, and 684, while the waveform 980 actuates the switches 940 and 945. It can be appreciated that the waveforms 975 and 980 are non-overlapping and alternate in time.

[0120]

[0121] When the control signal 975 closes the switches 685, 686, 683, and 684 (and the control signal 980 maintains the switches 940 and 945 open), the electrical signals from the sources 605 and 606 are conducted through the coupling capacitors 610 and 630 to the amplifiers 681 and 682, and also to the transducers 420 and 445, respectively. The transducers 420 and 445 convert the electrical signals into corresponding audio signals, thereby providing stereophonic playback to the user. The coupling capacitors 610 and 630 may provide direct-current (DC) blocking, thereby enhancing the quality of the signals conducted to the transducers 420 and 445. During this interval, the sources 425 and 440 remain electrically isolated from the differential amplifier 460 because the switches 940 and 945 are open, and therefore no biometric signal acquisition occurs. Furthermore, during this interval, the amplifiers 681 and 682 and the variable impedances 688, 689, 687, and 690 remain electrically isolated from the transducers 420 and 445, and do not affect the audio playback.

[0121]

[0122] When the control signal 975 opens the switches 685, 686, 683, and 684 (and the control signal 980 closes the switches 940 and 945), the sources 425 and 440, which may correspond to electrodes positioned on the left and right ears of the user, are coupled into amplifier 681 via variable impedances 688 and 689 and into amplifier 682 via variable impedances 687 and 690. The outputs of amplifiers 681 and 682 are coupled into the differential amplifier 460 through the switches 940 and 945. The amplifiers 681 and 682 together with their respective impedance pairs (impedances 688 and 689 for amplifier 681; impedances 687 and 690 for amplifier 682) form an AC bridge that can be tuned to adjust the effective transfer function of the transducers 420 and 445 in a specific frequency band of interest. Because the heart is anatomically closer to the left side of the body, the electrical signals detected at the two ears may share common components while also exhibiting differences attributable to cardiac activity. The differential amplifier 460 receives the outputs of amplifiers 681 and 682, suppresses common-mode interference, and retains the differential component that reflects the user’s heart activity. By leveraging the AC-bridge configuration and selective tuning of the effective transfer function of the transducers 420 and 445, the apparatus 900 may improve the signal-to-noise ratio (SNR) of the acquired biometric signals and reduce the mean bias absolute percentage error (MBAPE) in the estimation of biometric parameters such as heart rate.

[0122]

[0123] It is contemplated that the provision of the switches 940 and 945 at the input of the differential amplifier 460 may further disconnect the outputs of amplifiers 681 and 682 during audio playback, thereby suppressing leakage of residual signals into the differential amplifier 460, reducing noise coupling, and avoiding unnecessary power consumption in the biometric acquisition path.

[0123]

[0124] The output signal from the differential amplifier 460 may be provided to the sampling and anti-aliasing filter 470, which may include the sampling capacitor 260 described previously with reference to FIG. 2. The filter 470 may condition the output signal by attenuating high-frequency components and passing frequencies relevant to the biometric parameter. Once the sampling capacitor 260 charges to a predefined maximum threshold, the control circuitry 100 may open the switches 940 and 945 (and close the switches 685, 686, 683, and 684), decoupling the sources 425 and 440 from the differential amplifier 460. The sampling capacitor 260 then discharges, generating the measurement signal 250, which is processed by the measurement circuitry 200 as described previously with reference to FIG. 2.

[0124]

[0125] Once the sampling capacitor 260 discharges to a predefined minimum threshold, the control circuitry 100 may again close the switches 940 and 945 (and open the switches 685, 686, 683, and 684), repeating the alternating intervals between stereophonic playback and biometric signal acquisition. In some embodiments, the actuation frequency of the switches 685, 686, 683, 684, 940, and 945 may be higher than the human audible range of approximately 20 Hz to 20 kHz, such that no perceptible interruption occurs in the audio playback.

[0125]

[0126] FIG. 10 illustrates an audio apparatus 1000 for audio playback and biometric signal acquisition, in accordance with at least some non-limiting embodiments of the present technology.

[0126]

[0127] The apparatus 1000 may comprise an electrical source 1002 associated with an electrical signal indicative of audio playback, an electrical source 1020 associated with an electrical signal indicative of a biometric parameter, a coupling capacitor 1006, switches 1004, 1008, 1014, and 1026, transducer 1018, amplifiers 1010, 1012, and 1016, a feedback connection 1022 associated with amplifier 1010, an input resistor 1024 associated with amplifier 1012, a feedback resistor 1028 associated with amplifier 1012, a feedback connection 1030 associated with amplifier 1016, and a sampling and anti-aliasing filter 470 coupled to the measurement circuitry 200.

[0127]

[0128] The switches 1004, 1008, 1014, and 1026 are actuated by the control circuitry 100 (FIG. 1) in accordance with the timing waveforms 1032, 1034, and 1036. The waveform 1032 actuates the switches 1008 and 1026, the waveform 1034 actuates the switch 1014, and the waveform 1036 actuates the switch 1004. The waveforms 1032, 1034, and 1036 are non-overlapping and alternate in time such that audio playback and biometric signal acquisition occur in successive intervals without interference.

[0129] The waveforms 1032, 1034, and 1036 may be characterized by different duty cycles. For example, the duty cycle of waveform 1032, when actuating switch 1008 to conduct the electrical signal from the audio source 1002 to the transducer 1018 via the coupling capacitor 1006, may be longer than the duty cycles of waveforms 1034 and 1036 so as to support longer intervals of audio playback. By contrast, during biometric acquisition, the waveform 1034 may close the switch 1014 for a shorter interval to pass the biometric signal to the amplifier 1016. Furthermore, the waveform 1036 may close the switch 1004 for a very short time to allow discharge of the coupling capacitor 1006, thereby reducing audio leakage into the amplifiers 1012 and 1016. In this manner, longer playback intervals and shorter acquisition intervals are established to balance longer audio playback with reliable sampling of the biometric signal.

[0128]

[0130] The apparatus 1000 shown in FIG. 10 comprises an inverting amplifier 1012 positioned before the sample-and-hold block formed by the switch 1014 and the amplifier 1016. The feedback path of amplifier 1012 includes the switch 1026, which may be actuated synchronously with switch 1008 by the waveform 1032. The actuation of switch 1026 controls whether the feedback resistor 1028 is engaged, thereby adjusting the effective gain of the amplifier 1012.

[0129]

[0131] When the switch 1008 is open, the switch 1026 is also open, and the amplifier 1012 applies a gain to the biometric signal from the source 1020, the gain being equal to the negative ratio of the feedback resistor 1028 to the input resistor 1024.

[0130]

[0132] When the switch 1008 is closed, the switch 1026 also closes, thereby shorting the feedback resistor 1028. In this condition, the amplifier 1012 attenuates any residual audio leakage at its input by a factor determined by the ON-state resistance of the closed switch 1026 relative to the input resistor 1024. The effect of this attenuation is that any unwanted audio leakage that might reach amplifier 1012 is not amplified, but rather suppressed. As a result, only the desired biometric signal is amplified, and the apparatus 1000 avoids boosting unnecessary noise during audio playback.

[0133] The amplifier 1010 may be configured as a buffer or pre-amplifier stage for the biometric signal from the source 1020. The feedback connection 1022 supports stable operation of the amplifier 1010, for example, by maintaining its biasing and reducing distortion.

[0131]

[0134] During intervals when the waveform 1034 closes the switch 1014, the biometric signal processed by the amplifiers 1010 and 1012 is sampled and held by the combination of switch 1014 and amplifier 1016. The amplifier 1016 operates as a buffer stage with its feedback connection 1030, which maintains high input impedance and low output impedance, thereby preserving the integrity of the sampled biometric signal.

[0132]

[0135] The output from amplifier 1016 is provided to the sampling and anti-aliasing filter 470. The filter 470, which may include the sampling capacitor 260 described previously with reference to FIG. 2, conditions the signal by attenuating unwanted high-frequency components and retaining frequencies relevant to the biometric parameter.

[0133]

[0136] Once the sampling capacitor 260 within the filter 470 charges to a predefined maximum threshold, the control circuitry 100 may open the switches 1004, 1014, and 1026, decoupling the biometric source 1020 and amplifiers 1012, 1016 from the signal path. The capacitor 260 then begins to discharge, generating the measurement signal 250.

[0134]

[0137] The measurement circuitry 200 may process the measurement signal 250. For example, the high-impedance buffer 210 may minimize loading effects, the programmable gain amplifier 220 may adjust the signal amplitude, and the analog-to-digital converter 230 may digitize the signal for further analysis by the processor 240. The processor 240 may extract biometric information such as the heart-rate of the user.

[0135]

[0138] Once the sampling capacitor 260 discharges to a predefined minimum threshold, the control circuitry 100 may again actuate the waveforms 1032, 1034, and 1036 in their respective sequence, thereby repeating alternating intervals of audio playback and biometric acquisition. In some embodiments, the frequency of this alternation may be higher than the human audible range of approximately 20 Hz to 20 kHz, such that no perceptible interruption occurs in the playback experienced by the user.

[0136]

[0139] FIG. 11 illustrates an audio apparatus 1100 comprising a switched capacitor network 1199 for audio playback and biometric signal acquisition, in accordance with at least some non-limiting embodiments of the present technology.

[0137]

[0140] The apparatus 1100 may comprise an electrical source 1110 associated with an electrical signal indicative of audio playback, an electrical source 1160 associated with an electrical signal indicative of a biometric parameter, a switched- capacitor network 1199 comprising switches 1120 and 1130 and a capacitor 1140, a transducer 1150, a gain stage amplifier 1170, and a sampling and anti-aliasing filter 470 coupled to the measurement circuitry 200.

[0138]

[0141] The switches 1120 and 1130 operate in an alternating manner under the control of the control circuitry 100 (FIG. 1), in accordance with the timing waveforms 1180 and 1190. Together with the capacitor 1140, the switches 1120 and 1130 implement a switched-capacitor network 1199 that behaves as a variable resistor. The equivalent resistance Rsw of the network 1199 is inversely proportional to the product of the capacitance Cs of capacitor 1140 and the switching frequency f of the waveforms 1180 and 1190, as represented by the following expression:

[0139] Rsw = l / (Cs x f) (1)

[0140]

[0142] By achieving a variable resistance with the switched-capacitor network 1199, some embodiments may provide advantages in terms of compactness, suitability for integration in semiconductor circuits, and ease of control. By varying the control frequency f, the apparatus 1100 can adjust the effective resistance Rsw, thereby balancing the relative emphasis between the audio playback signal and the biometric acquisition signal.

[0141]

[0143] During one operational interval of the apparatus 1100, the control frequency f may be set high such that the equivalent resistance Rsw is very low. In this condition, most of the electrical signal from the audio source 1110 conducts to the transducer 1150, thereby generating high quality audio playback. During this interval, the biometric source 1160 is effectively isolated.

[0144] During another operational interval of the apparatus 1100, the control frequency f may be set low such that the equivalent resistance Rsw is very high. In this condition, the electrical signal from the audio source 1110 is strongly attenuated, and the electrical signal from the biometric source 1160 is conducted to the amplifier 1170, and subsequently to the sampling and anti-aliasing filter 470. The filter 470 conditions the signal from the biometric source 1160 by attenuating undesired high-frequency components and preserving the frequency components relevant to the biometric parameter. During this biometric signal acquiring interval, the lower bound of the control frequency f may be chosen such that the equivalent resistance Rsw still corresponds to a switching rate higher the audible frequency band (approximately 20 Hz to 20 kHz) so that the desired biometric signal is sampled reliably without audible artifacts in the playback experienced by the user.

[0142]

[0145] The output from the sampling and anti-aliasing filter 470 is supplied to the measurement circuitry 200. The ADC 230 digitizes the biometric signal, and the processor 240 analyzes the digital data to estimate one or more biometric parameters, such as the heart-rate of the user.

[0143]

[0146] In this way, the apparatus 1100 may leverage the switched-capacitor network 1199 to realize a variable resistance that supports selective balancing between long intervals of audio playback and short intervals of biometric acquisition, while minimizing size, complexity, and power consumption of the apparatus 1100.

[0144]

[0147] FIG. 12 illustrates an equivalent circuit 1200 of an audio apparatus for audio playback and biometric signal acquisition, in accordance with at least some non-limiting embodiments of the present technology.

[0145]

[0148] The equivalent circuit 1200 may be used to demonstrate an example configuration of the acquisition time of a biometric signal acquired using the apparatus. The equivalent circuit 1200 may comprise an electrical source 1210 associated with an electrical signal indicative of audio playback, a fixed series resistance 1220, a variable series resistance 1230, a sampling capacitor 1240, a parasitic capacitance 1250, and a load resistance 1260. The source 1210 provides an alternating electrical signal, which is conducted through the resistances 1220 and 1230 to the parallel combination 1290 of capacitors 1240, 1250 and the load resistance 1260. The parallel combination 1290 may be referred to as the resistive-capacitive (RC) network 1290.

[0146]

[0149] In some embodiments, the resistance 1220 may represent the output resistance of a previous stage, the resistance 1230 may represent a switchable or variable series resistance, the capacitor 1240 may represent a sampling capacitor, the capacitor 1250 may represent parasitic capacitances due to capacitive contributions from the printed circuit board of the apparatus, and the resistance 1260 may represent the input resistance of a subsequent amplifier stage.

[0147]

[0150] The values of the resistors 1220, 1230, 1260 and capacitors 1240, 1250 may be chosen such that the acquisition time is sufficient for charging the sampling capacitor 1240 to an accurate representation of the signal from the source 1210. The acquisition time depends on the switching frequency and the duty cycle of the control signals that actuate the switching associated with resistance 1230. For instance, in a non-limiting example, a switching frequency fsw= 50 kHz and a duty cycle of 99% for the switch 1299 associated with resistance 1230, the available acquisition time t may be expressed as: t = (1 / fsw)x(1 - duty cycle) (2)

[0148] Substituting fsw= 50 kHz and duty cycle = 0.99 in eq. (2), the acquisition time is: t = (1 / 50,000) x (1 - 0.99) s = 200 ns

[0149]

[0152] In a non-limiting example, the time constant T of the RC network 1290 may be defined as one-fifth of the acquisition time:

[0150] T = t / 5 = 200 ns / 5 = 40 ns

[0151]

[0151] The effective capacitance C of the RC network 1290 is the sum of the sampling capacitor 1240 and the parasitic capacitance 1250. In a non-limiting example, assuming Cs= 47 pF for the capacitor 1240 and Cp= 25 pF for the capacitor 1250, the effective capacitance of the RC network 1290 is:

[0152] C = Cs + Cp = 47 pF + 25 pF = 72 pF

[0154] The equivalent resistance Req of the RC network 1290 required to achieve the desired time constant is then:

[0153] Req = T / C = (40 X 109) / (72 X KF12) = 555.56 ohms

[0154]

[0155] If the resistance 1220 (output resistance of the previous stage) is approximately 10 ohms, the variable series resistance 1230 can then be selected as:

[0155] Rs= (555.56 - 10) ohms = 545.56 ohms

[0156]

[0152] In this way, FIG. 12 illustrates a non-limiting example of how circuit parameters such as sampling capacitance 1240, parasitic capacitance 1250, variable series resistance 1230, and the fixed series resistance 1220 may be selected to achieve a desired acquisition time t for reliable sampling of the biometric signal.

[0157]

[0153] It should be expressly understood that not all technical effects mentioned herein need to be enjoyed in each and every embodiment of the present technology.

[0158]

[0154] Modifications and improvements to the above-described implementations of the present technology may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the present technology is therefore intended to be limited solely by the scope of the appended claims.

Claims

CLAIMS1. An audio apparatus, comprising: at least one transducer (325) configured to convert a first electrical signal into an audio signal; an electrically conductive path configured to conduct, via a switching network (160),(i) the first electrical signal to the at least one transducer (325), and(ii) a second electrical signal to a sampling capacitor (260), the switching network (160) comprising: at least one first switch (350) configured to selectively couple the at least one transducer (325) to the electrically conductive path; at least one second switch (340) configured to selectively couple the sampling capacitor (260) to the electrically conductive path; a control circuitry (100) configured to actuate the switching network (160), the actuating the switching network (160) comprising: during a first interval of time, decoupling the at least one transducer (325) from the electrically conductive path and coupling the sampling capacitor (260) to the electrically conductive path, to charge the sampling capacitor (260) with the second electrical signal; during a second interval of time, coupling the at least one transducer (325) to the electrically conductive path and decoupling the sampling capacitor (260) from the electrically conductive path, to conduct the first electrical signal to the at least one transducer (325); anda measurement circuitry (200) coupled to the sampling capacitor (260) and configured to generate, during the second interval and from charge held by the sampling capacitor (260), a measurement signal (250) indicative of a biometric parameter associated with a user of the audio apparatus.

2. The audio apparatus of claim 1 , wherein the electrically conductive path further comprises a coupling capacitor (330) disposed in series with the at least one first switch (350).

3. The audio apparatus of any one of claims 1 and 2, wherein the control circuitry (100) is further configured to control the at least one first switch (350) and the at least one second switch (340) in an alternating manner, such that the first interval and the second interval are mutually exclusive.

4. The audio apparatus of any one of claims 1 to 3, wherein the sampling capacitor (260) is configured to retain charge for a duration extending through the second interval.

5. The audio apparatus of any one of claims 1 to 4, wherein the control circuitry (100) comprises a signal generator (120) configured to produce control signals (150) to alternately actuate the at least one first switch (350) and the at least one second switch (340).

6. The audio apparatus of any one of claims 1 to 5, wherein the measurement circuitry (200) comprises an analog-to-digital converter (230) configured to digitize the measurement signal (250).

7. The audio apparatus of any one of claims 1 to 6, wherein the sampling capacitor (260) is implemented as part of a sampling and anti-aliasing filter (470).

8. The audio apparatus of any one of claims 1 to 7, wherein the biometric parameter is indicative of at least a heart-rate of the user.

9. The audio apparatus of any one of claims 1 to 8, wherein the first electrical signal is indicative of a monophonic sound.

10. The audio apparatus of any one of claims 1 to 8, wherein the first electrical signal is indicative of a stereophonic sound.

11. The audio apparatus of any one of claims 1 to 10, further comprising: an other transducer (445), the other transducer (445) configured to convert an other electrical signal into an other audio signal; an other first switch (435), the other first switch (435) configured to selectively couple the other transducer (445) to the electrically conductive path; a differential amplifier (460) configured to generate an output signal indicative of a difference between the first electrical signal and the other electrical signal, the output signal utilized by the measurement circuitry (200) to generate the measurement signal (250).

12. The audio apparatus of claim 11, wherein the first electrical signal and the other electrical signal correspond to a same electrical source (405).

13. The audio apparatus of claim 11, wherein the first electrical signal corresponds to a first electrical source (505) and the other electrical signal corresponds to an other electrical source (506).

14. The audio apparatus of any one of claims 1 to 13, wherein the at least one first switch (415) and the other first switch (435) are implemented as single-pole single-throw (SPST) switches to form an alternating-current (AC) bridge.

15. The audio apparatus of any one of claims 1 to 14, wherein the at least one second switch (740, 745) is disposed at an input of the differential amplifier (460).

16. The audio apparatus of any one of claims 1 to 14, wherein the at least one second switch (465) is disposed at an output of the differential amplifier (460).

17. The audio apparatus of any one of claims 1 to 16, further comprising an inverting amplifier (1012) disposed between the at least one first switch (1008) and the at least one second switch (1014), the inverting amplifier (1012) comprising a feedback loop comprising a gain-control switch (1026), the gain-control switch (1026) configured to vary a feedback resistance (1028), to control a gain of the inverting amplifier (1012).

18. The audio apparatus of any one of claims 2 to 17, further comprising a discharge switch (1004) coupled to a node of the electrically conductive path and configured to selectively discharge the coupling capacitor (1006).

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