Abstract:
A hearing aid includes at least one capacitive switch for controlling or communicating with the hearing aid by touch. The capacitive switch is an electrode on the inside of the housing coupled to a touch detector. Touching the outside of the hearing aid adjacent the electrode produces a switching operation. The hearing aid includes a programmed microprocessor coupled to the touch detector. The microprocessor is programmed to effect predetermined functions in response to particular touch patterns.

Description:
[0001]    This invention relates to hearing aids and, in particular, to a hearing aid in which a capacitive switch is used for operating the hearing aid. 
       BACKGROUND TO THE INVENTION 
       [0002]    Hearing aids having switches or control surfaces are known in the art. For example, U.S. Pat. No. 2,971,065 (Busse) discloses an In-The Ear (ITE) hearing aid having a switch for turning the hearing aid on or off. U.S. Pat. No. 5,463,692 (Fackler) discloses a Behind-The-Ear (BTE) hearing aid with switches for controlling the operation of the hearing aid. 
         [0003]    It is known in the art to control or program a hearing aid using radio frequency (RF) transmissions. It is also known in the art to transmit data to a hearing aid having a diode sensitive to infrared radiation; see U.S. Pat. No. 6,229,900 (Leenen). Remote controls for hearing aids are no less likely to be misplaced or need new batteries than remote controls for any other device. It is desired to eliminate the tedium of needing a remote control. 
         [0004]    A mechanical switch requires that one have an opening in the housing of a hearing aid. Moisture, wax, dirt, oils and so on, can work their way into the housing, causing problems. It is preferable that a hearing aid be made relatively impervious to ambient conditions. 
         [0005]    U.S. Patent Application Publication 2005/0141740 discloses that “the use of higher voltages from the various voltage taps of battery 310 may be used [sic] to turn off and on hearing aid 300 via non mechanical switch means such as a membrane switch, a capacitive switch, a piezo switch, etc.” There is no other disclosure in the publication concerning a capacitive switch. 
         [0006]    In view of the foregoing, it is therefore an object of the invention to provide a hearing aid with a capacitive switch for communication and control. 
         [0007]    Another object of the invention is to provide a capacitive switch for a BTE hearing aid. 
         [0008]    A further object of the invention is to provide a capacitive switch for an ITE hearing aid. 
         [0009]    Another object of the invention is to provide a hearing aid that is relatively impervious to ambient conditions. 
       SUMMARY OF THE INVENTION 
       [0010]    The foregoing objects are achieved by this invention in which a hearing aid includes at least one capacitive switch for controlling or communicating with the hearing aid by touch. The capacitive switch is an electrode on the inside of the housing coupled to a touch detector. Touching the outside of the hearing aid adjacent the electrode produces a switching operation. The hearing aid includes a programmed microprocessor coupled to the touch detector. The microprocessor is programmed to effect predetermined functions in response to particular touch patterns. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    A more complete understanding of the invention can be obtained by considering the following detailed description in conjunction with the accompanying drawings, in which: 
           [0012]      FIG. 1  illustrates a BTE hearing aid constructed in accordance with a preferred embodiment of the invention; 
           [0013]      FIG. 2  illustrates an ITE hearing aid constructed in accordance with the invention; and 
           [0014]      FIG. 3  illustrates the operation of a hearing aid constructed in accordance with the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    In  FIG. 1 , hearing aid  10  includes housing  11  coupled to earpiece  12  by cable  14 . Within housing  11  are battery  16  and circuit board  17 . Circuit board  17  includes programmed microprocessor  18  and other circuitry for processing audio signals, charging battery  16 , and other functions. A speaker (not shown) is located in earpiece  12  and a microphone (not shown) is located in housing  11 . The speaker is coupled to circuit board  17  by wires  21  in cable  14 . 
         [0016]    For historical reasons, a speaker is sometimes referred to as a “receiver” in the hearing aid art. That is not the terminology being used herein. A hearing aid has at least one speaker and at least one microphone. 
         [0017]    In accordance with the invention, hearing aid  10  includes electrode  23  located underneath a portion of housing  11 . Electrode  23  is electrically coupled to circuit board  17  and is a capacitive touch sensor. Electrode  23  is preferably located on the inside of the convex surface of a BTE hearing aid. Electrode  23  is then generally perpendicular to the skin on the skull and to the auricle, thereby minimizing capacitive coupling to these tissues. An electrode can be located elsewhere, as indicated by electrode  24  but the adjustment for touch is more sensitive. More than one electrode can be used, as indicated by electrode  25 . 
         [0018]    In  FIG. 2 , ITE hearing aid  30  includes housing  31  containing battery  33 , electronics  36 , and speaker  35 . Speaker  35  is coupled to the ear canal by tube  38 . The bulk of the hearing aid rests in the outer ear. In accordance with the invention, hearing aid  30  includes electrode  39 . This electrode is electrically coupled to electronics  36  and is a capacitive touch sensor. As illustrated in  FIG. 2 , electrode  39  is located on the inside surface of the outer or distal portion of body  31 . 
         [0019]      FIG. 3  illustrates the construction and operation of the invention. Housing  41  is made from a suitable polymer and is dielectric. Electrode  42  is applied to the inside surface of housing  41 . Electrode  42  can be a pre-formed plate bonded to housing  41 , or etched, plated, painted, or sprayed onto housing  41 . A user touches the opposite side (outside) of the housing in order to operate the switch. The electric field created by electrode  42 , as represented by dashed lines  43  and  44 , is distorted by capacitive coupling to hand  46 . The change in capacitance is detected by detector  51 . 
         [0020]    In one embodiment of the invention, a QT102  QTOUCH ™ toggle-mode charge-transfer IC, commercially available from Quantum Research Group, was used as the detector. The detector operates by charging a sense electrode of unknown capacitance to a known potential. The resulting charge is transferred into a measurement circuit including capacitor  52 . By measuring the charge after one or more charge-and-transfer cycles, the capacitance of the sense electrode can be determined. Placing a finger on the opposite side of the dielectric introduces external capacitance that affects the flow of charge. The detector includes circuitry to reduce false positives, e.g. requiring four consecutive positives within a time limit and randomized charging pulses. 
         [0021]    In a prototype of the invention, electrode  23  ( FIG. 1 ) was a brass sheet approximately 6 mm×4 mm covered with a section of the side wall from a mini-BTE hearing aid. Touch was accurately sensed. In another prototype, electrode  23  was built up on the inside of a BTE housing by spraying nickel shielding and covering the nickel with Kapton® polyimide tape. 
         [0022]    In accordance with another aspect of the invention, signal processing means detects the number and duration of touches for controlling a hearing aid. For example, a long contact, e.g. four seconds, turns the hearing aid on and off. (Obviously, the detector remains on even though the audio processing circuitry is turned off). A short, double tap, can be used for adjusting volume or operating mode. Alternatively, more than one electrode is used, each having one or more dedicated functions. 
         [0023]    The invention thus provides a hearing aid with a capacitive switch for communication and control. The switch is compatible with a BTE hearing aid, an ITE hearing aid, and other types of hearing aids. The switch is contained within the housing for a hearing aid, enabling the housing to be relatively impervious to ambient conditions. 
         [0024]    Having thus described the invention, it will be apparent to those of skill in the art that various modifications can be made within the scope of the invention. For example, the microprocessor can include circuitry for detecting touch, rather than having a separate integrated circuit. Charge transfer is only one of several known ways to measure capacitance. For example, electrode  42  could be part of a tuned circuit or part of a resonant circuit in an oscillator. Changes in center frequency or oscillating frequency are sensed to detect changes in capacitance.