Patent Publication Number: US-8971558-B2

Title: Hearing device with external electrode

Description:
TECHNICAL FIELD 
     The present invention relates to a hearing device with one or more external electrodes. More specifically, the present invention relates to a hearing device such as e.g. a hearing aid, a listening device, an earphone or a headset, which has one or more electrodes intended to be in contact with the skin of a user of the hearing device. 
     The invention may e.g. be useful in applications such as a hearing aid for compensating for a hearing-impaired person&#39;s loss of hearing capability, a listening device for augmenting a normal-hearing person&#39;s hearing capability, an earphone for conveying electronic audio signals to the user or a headset for communicating with another person. 
     BACKGROUND ART 
     US patent application 2009/0209303 A1 discloses a wireless headset with a thermoelectric device, a regulator and an energy storage element, e.g. a rechargeable battery. One side of the thermoelectric device is thermally connected through thermally conductive material, e.g. a high density conductive polymer, to the user&#39;s body and is thus subjected to a temperature close to the temperature of the user&#39;s skin, whereas the other side is thermally connected through thermally conductive material to solar cells subjected to ambient temperature. The thermoelectric device converts a temperature difference between the user&#39;s skin and the solar cells into an electric current, which is supplied to the energy storage element through the regulator in order to provide power for operation of the wireless headset. 
     The thermally conductive material occupies a relatively large portion of the outside surface of the wireless headset. 
     German patent application DE 10 232 376 A discloses a thermoelectric element and the use of it for powering a hearing aid. The thermoelectric element comprises a stack of electrically conductive and electrically insulating layers, and the electrically conductive layers may comprise an electrically conductive polymer. 
     European patent application EP 2 200 347 A2 discloses a hearing aid having electrodes for measuring an electroencephalogram (EEG). The electrodes may be manufactured in the surface of a hearing aid shell. The hearing aid may further have a thermo element for measuring the body temperature of the hearing-aid user and being located where the hearing aid meets the skin surface. 
     European patent application EP 2 299 731 A1 discloses a listening device wherein charging pads for charging a rechargeable battery are arranged on a housing portion intended for placement in the ear canal during use of the listening device. 
     The electrodes and charging pads disclosed in the above mentioned prior art also occupy significant portions of the outside surfaces of the respective device housings. 
     DISCLOSURE OF INVENTION 
     Devices intended for placement at the ear, in the ear or in the ear canal of an individual, i.e. a user, generally have a relatively small surface area, which limits the number, the size and the freedom for placement of thermally conductive areas, electrodes and/or charging pads such a device may have. This makes it difficult to combine functions requiring such thermally conductive areas, electrodes and/or charging pads in one and the same device. 
     It is an object of the present invention to provide a device, which does not suffer from the above problem. 
     This and other objects of the invention are achieved by the invention defined in the accompanying independent claims and as explained in the following description. Further objects of the invention are achieved by the embodiments defined in the dependent claims and in the detailed description of the invention. 
     By sharing electrically and/or thermally conductive surface portions between different functional elements of a hearing device, the required surface area may be reduced and/or the surface portions may be placed with increased freedom. 
     In the present context, a “hearing device” refers to a device, such as e.g. a hearing aid, a listening device or an active ear-protection device, which is adapted to improve, augment and/or protect the hearing capability of a user by receiving acoustic signals from the user&#39;s surroundings, generating corresponding audio signals, possibly modifying the audio signals and providing the possibly modified audio signals as audible signals to at least one of the user&#39;s ears. A “hearing device” further refers to a device such as an earphone or a headset adapted to receive audio signals electronically, possibly modifying the audio signals and providing the possibly modified audio signals as audible signals to at least one of the user&#39;s ears. Such audible signals may e.g. be provided in the form of acoustic signals radiated into the user&#39;s outer ears, acoustic signals transferred as mechanical vibrations to the user&#39;s inner ears through the bone structure of the user&#39;s head and/or electric signals transferred directly or indirectly to the cochlear nerve of the user. The hearing device may be configured to be worn in any known way, e.g. as a unit arranged behind the ear with a tube leading radiated acoustic signals into the ear canal or with a loudspeaker arranged close to or in the ear canal, as a unit entirely or partly arranged in the pinna and/or in the ear canal, as a unit attached to a fixture implanted into the skull bone, etc. More generally, a hearing device comprises an input transducer for receiving an acoustic signal from an user&#39;s surroundings and providing a corresponding input audio signal and/or a receiver for electronically receiving an input audio signal, a signal processing circuit for processing the input audio signal and an output transducer for providing an audible signal to the user in dependence on the processed audio signal. In some hearing devices, an amplifier may constitute the signal processing circuit. 
     A “hearing system” refers to a system comprising one or two hearing devices, and a “binaural hearing system” refers to a system comprising one or two hearing devices and being adapted to cooperatively provide audible signals to both of the user&#39;s ears. Hearing systems or binaural hearing systems may further comprise “auxiliary devices”, which communicate with the hearing devices and affect and/or benefit from the function of the hearing devices. Auxiliary devices may be e.g. remote controls, audio gateway devices, mobile phones, public-address systems, car audio systems or music players. Hearing devices, hearing systems or binaural hearing systems may e.g. be used for compensating for a hearing-impaired person&#39;s loss of hearing capability, augmenting or protecting a normal-hearing person&#39;s hearing capability and/or conveying electronic audio signals to a person. 
     As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well (i.e. to have the meaning “at least one”), unless expressly stated otherwise. It will be further understood that the terms “has”, “includes”, “comprises”, “having”, “including” and/or “comprising”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof. It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or intervening elements may be present, unless expressly stated otherwise. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless expressly stated otherwise. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in more detail below in connection with preferred embodiments and with reference to the drawings in which: 
         FIG. 1  shows an embodiment of a hearing device according to the invention. 
     
    
    
     The FIGURE is schematic and simplified for clarity, and it just shows details, which are essential to the understanding of the invention, while other details are left out. Throughout, like reference numerals and/or names are used for identical or corresponding parts. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art from this detailed description. 
     MODE(S) FOR CARRYING OUT THE INVENTION 
     The hearing device  1  shown in  FIG. 1  comprises a microphone  2 , a preamplifier  3 , a digitiser  4 , a signal processor  5 , a power amplifier  6  and a loudspeaker  7  constituting an audio signal path. The hearing device  1  further comprises a housing  8 , which is adapted to be arranged in an operating position at an ear, in an ear or in an ear canal of a user of the hearing device  1 . The microphone  2  is arranged to receive an acoustic input signal from the user&#39;s surroundings and provide a corresponding microphone signal to the preamplifier  3 . The preamplifier  3  is adapted to amplify the microphone signal and provide the amplified microphone signal to the digitiser  4 . The digitiser  4  is adapted to digitise the amplified microphone signal and provide a digitised audio signal to the signal processor  5 , which is adapted to modify the digitised audio signal in accordance with the purpose of the hearing device  1 , e.g. to improve or augment the hearing capability of the user and/or to amplify or convey a received audio signal to the user. The signal processor  5  is adapted to provide the modified audio signal to the power amplifier  6 , which may e.g. comprise a pulse-width modulator, which is adapted to provide a corresponding amplified and/or pulse-width modulated signal to the loudspeaker  7 . The loudspeaker  7  is arranged to transmit an acoustic output signal corresponding to the amplified and/or pulse-width modulated signal to the user. 
     The hearing device  1  further comprises a first and a second electrode  9 ,  10 , which each constitute an outer surface portion of the housing  8 . The electrodes are separate from each other and are arranged such that they each abut the user&#39;s skin when the housing  8  is in the operating position. The electrodes  9 ,  10  are preferably arranged such that the length of the electric connection between the electrodes  9 ,  10  through the user&#39;s skin is as large as possible with the given housing  8  in the operating position. The electrodes  9 ,  10  may e.g. be arranged at opposite sides of the housing  8 , and/or, in the case of an elongate housing  8 , at opposite ends of the housing  8 . The hearing device  1  further comprises a thermally conductive body  11 , which constitutes a further outer surface portion of the housing  8  and which is arranged such that it is subjected to ambient temperature when the housing  8  is in the operating position. The thermally conductive body  11  is preferably arranged at the same end or side of the housing  8  at which the microphone  2  or a sound inlet to the microphone  2  is arranged. 
     The hearing device  1  further comprises a brain-wave measurement circuit  12  that is electrically connected to receive measurement signals from the first electrode  9  via a first electric connection  13  and from the second electrode  10  via a second electric connection  14 . The brain-wave measurement circuit  12  is adapted to determine and provide brain-wave signals comprising e.g. electroencephalograms (EEG) and/or auditory brainstem responses (ABR) in dependence on the measurement signals. The brain-wave measurement circuit  12  may comprise preamplifiers (not shown) adapted to amplify measurement signals. 
     The hearing device  1  further comprises a communication circuit  15  that is electrically connected to receive and transmit communication signals from/to the first electrode  9  via the first electric connection  13  and from/to the second electrode  10  via the second electric connection  14 . The communication circuit  15  is adapted to determine and provide receive data in dependence on received communication signals and to transmit communication signals in dependence on transmit data provided to the communication circuit  15 . The communication signals are preferably capacitively or conductively coupled to the user&#39;s skin such that they may pass through the user&#39;s body, e.g. to/from a second hearing device arranged at the user&#39;s other ear and/or to/from a further device arranged on the user&#39;s body. In some embodiments, the communication circuit  15  is not electrically connected to a second electrode  10 , in which case the second electrode  10  and the second electric connection  14  may be omitted. 
     The hearing device  1  further comprises a touch-sensing circuit  16  that is electrically connected to transmit sensing signals to the first electrode  9  via the first electric connection  13  and to the second electrode  10  via the second electric connection  14 . The touch-sensing circuit  16  is adapted to determine variations in the sensing signals, to determine and/or classify touch events in dependence on the determined variations and to provide corresponding touch event signals in dependence on the determined and/or classified touch events. In some embodiments, the touch-sensing circuit  16  is not electrically connected to a second electrode  10 , in which case the second electrode  10  and the second electric connection  14  may be omitted. The touch-sensing circuit  16  may transmit sensing signals at multiple frequencies and determine and/or classify touch events in dependence on the relationship between determined variations in the sensing signals at different frequencies. 
     The hearing device  1  further comprises a thermoelectric generator  17  having a first thermally responsive surface that is thermally connected to the outer surface of the housing  8  mainly through a first thermal connection  18  via the first electrode  9  and a second thermally responsive surface that is thermally connected to the outer surface of the housing  8  mainly through a second thermal connection  19  via the thermally conductive body  11 . The thermoelectric generator  17  is adapted to provide a first charging current when the first and the second thermally responsive surfaces are subjected to different temperatures. The thermoelectric generator  17  may have a relatively flat shape with the thermally responsive surfaces arranged at opposite sides. The thermoelectric generator  17  may comprise one or more thermoelectric generator cells (not shown) each being adapted to convert a temperature difference into an electric voltage according to the so-called Seebeck effect. In the case that the thermoelectric generator  17  comprises more than one thermoelectric generator cell, such as e.g. about 10, about 100 or about 500 cells, the cells are preferably connected in parallel with respect to the temperature exposure. The cells may thus e.g. be arranged as a two-dimensional array having two larger surfaces that constitute the respective thermally responsive surfaces of the thermoelectric generator  17 . The array may preferably be curved in the third dimension in order to allow arrangement on a non-planar surface on or in the hearing device  1 . Electrically, the cells may be connected in parallel, in series or in any combination hereof, depending on the desired output voltage and/or output current. 
     The hearing device  1  further comprises a charge control circuit  20  and a rechargeable battery  21 , which is connected to supply power to the electronic circuits of the hearing device  1 . The charge control circuit  20  is connected to the first electrode  9  via the first electric connection  13  and to the second electrode  10  via the second electric connection  14 . The charge control circuit  20  is adapted to sink a second charging current when a charging voltage is applied across the electrodes  9 ,  10  and to convert the first and/or the second charging current into a third charging current and provide the third charging current to the rechargeable battery  21 . The first and second electrodes  9 ,  10  thus serve as charging pads. In some embodiments, the charge control circuit  20  is not connected to an electrode  9 ,  10 , in which case the second electrode  10  and the second electric connection  14  may be omitted. In this case, a power converter, which is adapted to modify the voltage of the electric power output from the thermoelectric generator  17 , may replace the charge control circuit  20 . In some embodiments, the hearing device  1  comprises a capacitive energy storage, e.g. a capacitor, or another type of rechargeable power storage instead of the rechargeable battery  21 . 
     The brain-wave measurement circuit  12 , the communication circuit  15 , the touch-sensing circuit  16  and/or the thermoelectric generator  17  may comprise protection circuits (not shown) adapted to protect the respective circuits  12 ,  15 ,  16 ,  17  against possible damage caused e.g. by a charging voltage applied to the first and/or second electrodes  9 ,  10  and/or by voltages received and/or provided by the respective other ones of the circuits  12 ,  15 ,  16 ,  17 . 
     The hearing device  1  further comprises a control unit  22 , which is connected to receive the brain-wave signals from the brain-wave measurement circuit  12 , the receive data from the communication circuit  15  and the touch event signals from the touch-sensing circuit  16 . The control unit  22  is further connected to provide the transmit data to the communication circuit  15  as well as to receive and provide various data, such as e.g. audio signals, status information, settings and commands, from/to the signal processor  5 . The control unit  22  is adapted to control the signal processing in the signal processor  5  in dependence on the brain-wave signals, the receive data and/or the touch event signals, as well as to provide the transmit data in dependence on the brain-wave signals, the receive data, the touch event signals and/or data received from the signal processor  5 . The control unit  22  may e.g. be adapted to compare the brain wave signals to predetermined patterns in order to estimate or classify the user&#39;s state and/or physical actions. The control unit  22  may further be adapted to combine information in the brain-wave signals with information in the touch event signals in order to increase the reliability of the determination of touch events, e.g. by comparing or otherwise deriving a measure of correlation between the respective signals. Thus, determined touch events may be used for remote control of the hearing device  1 . 
     The signal processor  5  is adapted to adjust its modification of the digitised audio signal in response to information comprised in the data received from the control unit  22  and/or to provide the modified audio signal in dependence on an audio signal comprised in these data. This allows the hearing device  1  to change its audio signal processing in response to e.g. commands, status information and/or audio signals received from a remote device, and/or to include such audio signals in the acoustic signal transmitted by the loudspeaker  7 . The remote device could e.g. be a remote control, a second hearing device located at or in the respective other ear of the user or an auxiliary device, e.g. a so-called audio gateway device, adapted to transmit an audio signal from an external device, such as e.g. a mobile phone or a TV set, to the hearing device  1 . The hearing device  1  may thus be part of a binaural hearing system. 
     The hearing device  1  may comprise a wireless transceiver  23  for receiving and transmitting wireless communication signals, such as e.g. inductive, radio-frequency (RF) or optical signals. The wireless transceiver  23  may be adapted to receive a wireless signal from a further device and to provide the audio input signal to the preamplifier  3  in dependence on the received wireless signal. The hearing device  1  may comprise switching means  24  for switching between receiving the audio input signal from the wireless transceiver  23  and receiving the audio input signal from the microphone  2 . The wireless transceiver  23  may perform any combination of the functions described above for the communication circuit  15  and may thus partly or completely replace and/or augment the communication circuit  15 . In some embodiments, a wireless receiver may replace the wireless transceiver  23 . In an embodiment, the communication circuit  15  is adapted to provide the input audio signal in dependence on a wireless signal received from a further device via the first and/or the second electrode  9 ,  10  and thus constitutes the wireless receiver  23 . 
     The brain-wave measurement circuit  12 , the communication circuit  15 , the touch-sensing circuit  16 , the thermoelectric generator  17  and the charge control circuit  20  each constitute an element of a group. In an embodiment, the hearing device  1  comprises two different elements, i.e.:
         the brain-wave measurement circuit  12  and the communication circuit  15 ;   the brain-wave measurement circuit  12  and the touch-sensing circuit  16 ;   the brain-wave measurement circuit  12  and the thermoelectric generator  17 ;   the brain-wave measurement circuit  12  and the charge control circuit  20 ;   the communication circuit  15  and the touch-sensing circuit  16 ;   the communication circuit  15  and the thermoelectric generator  17 ;   the communication circuit  15  and the charge control circuit  20 ;   the touch-sensing circuit  16  and the thermoelectric generator  17 ;   the touch-sensing circuit  16  and the charge control circuit  20 ; or   the thermoelectric generator  17  and the charge control circuit  20 .       

     In another embodiment, the hearing device  1  comprises three different elements  12 ,  15 ,  16 ,  17 ,  20 . In a further embodiment, the hearing device  1  comprises four different elements  12 ,  15 ,  16 ,  17 ,  20 . In any embodiment, two or more separate electrodes may replace the second electrode  10 , in which case each of such separate electrodes may instead of the second electrode  10  be connected to one or more of the comprised elements. In the extreme case, each of the elements  12 ,  15 ,  16 ,  20  may be connected to different ones of such separate electrodes. Any or all of such separate electrodes, the first electrode  9 , the second electrode  10 , the thermally conductive body  11 , the first thermal connection  18  and the second thermal connection  19  may comprise an electrically conductive polymer, thus allowing it/them to be resilient. Any or all of such separate electrodes, the first electrode  9 , the second electrode  10  and the thermally conductive body  11  may be covered by a material comprising graphene, or alternatively by a material comprising carbon and titanium, in order to achieve a biocompatible surface. 
     The signal processor  5 , the communication circuit  15  and the control unit  22  are preferably implemented mainly as digital circuits operating in the discrete time domain, but any or all portions hereof may alternatively be implemented as analog circuits operating in the continuous time domain. The same applies to such portions of the brain-wave measurement circuit  12 , the touch-sensing circuit  16 , the thermoelectric generator  17  and the charge control circuit  20  that may be implemented digitally. Such digital circuits may be implemented in any suitable combination of hardware, firmware and software and/or in any suitable combination of hardware units. Furthermore, any single hardware unit may execute the operations of several functional blocks in parallel or in interleaved sequence and/or in any suitable combination thereof. 
     Further modifications obvious to the skilled person may be made to the disclosed method, system and/or device without deviating from the scope of the invention. Within this description, any such modifications are mentioned in a non-limiting way. The possible modifications below are mentioned as examples hereof. 
     Some preferred embodiments have been described in the foregoing, but it should be stressed that the invention is not limited to these, but may be embodied in other ways within the subject-matter defined in the following claims. For example, the features of the described embodiments may be combined arbitrarily, e.g. in order to adapt the system, the devices and/or the method according to the invention to specific requirements. 
     It is further intended that the structural features of the system and/or devices described above, in the detailed description of ‘mode(s) for carrying out the invention’ and in the claims can be combined with the methods, when appropriately substituted by a corresponding process. Embodiments of the methods have the same advantages as the corresponding systems and/or devices. 
     Any reference numerals and names in the claims are intended to be non-limiting for their scope.