Abstract:
A hearing enhancement system, for co-operation with a conventional hearing aid used in T-switch mode, comprises a microphone ( 10 ), an electronics module ( 22 ) including an amplifier and a power supply, and an induction loop ( 12 ). The induction loop ( 12 ) has a small number (typically 10-20) of conductor turns formed as a flexible assembly of a size suitable to be worn around the body as a sash or belt.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a system for enhancing the hearing of persons who are hard of hearing and use conventional hearing aids. 
     Hearing aids as conventionally used are equipped with a T switch which allows inductive coupling of the hearing aid with the ear-piece of a telephone handset. Similar inductive coupling can also be provided by an induction loop to which audio signals are fed via a microphone and amplifier. Inductive loops of this nature are conventionally provided in public places such as churches and halls, the loop being positioned around the public space and fed from a microphone used by a spearer. It is of the essence of loops of this nature that the same signals will be heard by persons using hearing aids at any position within the loop. 
     It is also known to provide more localised induction loops to enable staff dealing with the public, for example, at Post Offices and railway ticket offices, to converse with a customer. Such installations, however, suffer from the disadvantages that they are relatively complex and expensive to install, and they have a low level of privacy which may be of concern to the hard of hearing in locations such as banks. They also have the drawback that the hearing enhancement can only be provided at fixed locations, and they are therefore unsuitable for use in situations such as large showrooms or hospital consulting suites. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a system for aiding communication with the hard of hearing which avoids or reduces the foregoing disadvantages. 
     The present invention accordingly provides a hearing enhancement system for use by a first person in communicating with a second person, one or the persons having impaired hearing and using a hearing aid equipped with a selectively actuable inductive coupling (or T switch); the system comprising a microphone, an amplifier, a power supply, and an inductive loop; at least the amplifier power supply and inductive loop being connected together as a unitary article adapted to be readily worn on and removed from the body of one of the persons, and in which the inductive loop is a flexible elongate member which, in use, is worn around the body of said person. 
     The flexible elongate member may be a permanently closed loop of a size to be worn draped from one shoulder across the user&#39;s body. Alternatively, the flexible elongate member may be provided with a releasable closure to enable it to be worn around the waist in the manner of a waist belt. 
     In one form, the microphone, the amplifier and the power supply are secured directly to the flexible elongate member. Where the flexible elongate member is worn draped across one shoulder, the amplifier and/or the power supply may be positioned at the lowest point of the loop adjacent to the user&#39;s waist, with the microphone positioned on the loop to be adjacent to the user&#39;s chest or shoulder. Alternatively, a separate microphone may be used. 
     The power supply may conveniently comprise a re-chargeable battery pack of the type used in portable telephones, or photovoltaic cells, or a combination of these. 
     The inductive loop may be formed by a length of flexible flat ribbon cable of a type well known per se. The ends of the length of ribbon cable may be joined together by a connector assembly with the conductors of the cable offset by one pitch, thereby forming a multi-turn coil. A 10 conductor or 20 conductor ribbon cable will be suitable for many applications. 
     The inductive loop or each inductive loop has between 5 and 50 turns. The inductive loop may alternatively be in the form of insulated single-conductor wire wound into a loop which may, for example, be enclosed in a soft plastic sleeve. 
     Preferably, the inductive loop is provided with switching means by which the user may select a smaller or a larger number of turns (for example, 10 or 20 turns) to provide a selection of very close range (c. 1 m) or close range (c. 2-3 m) communication. Alternatively, there may be a single loop driven by an amplifier the gain of which may be switched between low and high by the user. 
     One embodiment of the present invention will now be described, by way of example only, with reference to the drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a basic circuit diagram of a hearing enhancement system, 
     FIG. 2 is a schematic perspective view showing one embodiment of the present invention in use, 
     FIG. 3 illustrates the connection of a cable used in the embodiment of FIG. 2, 
     FIG. 4 shows a modified embodiment and 
     FIG. 5 is a block diagram of the embodiment of FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, the system includes a microphone  10  which detects the speech of a user and generates corresponding electrical signals in an induction coil  12  via an amplifier  14 . The amplifier  14  is powered by a power supply  16  and may be provided with volume and tone controls as indicated at  18  and  20 . 
     The power supply  16  may comprise a rechargeable battery pack, for example similar to those used in cellular telephones. Alternatively, photovoltaic cells may be used. A particularly preferred form of power supply is to use a combination of rechargeable batteries and photovoltaic cells, which eliminates the need for any intervention by the user such as recharging from mains or replacement of batteries. 
     Turning to FIG. 2, the system of the present invention is a unitary self-contained system which may be worn around the user. To this end, the induction coil  12  is in the form of a flexible loop which can be draped over the user&#39;s shoulder and around his upper body, and the microphone  10  plus a box  22 , housing the power supply and the amplifier, are secured to the flexible loop coil  12 . The most convenient arrangement is to have the box  22  and the lowest point of the loop, adjacent to the user&#39;s waist, and the microphone  10  secured to the loop  12  high on the user&#39;s chest to readily detect the user&#39;s speech. 
     The microphone  10  may suitably be provided in the form of two microphones facing in opposite directions along the plane of the loop  12 , and acoustically in antiphase. This reduces the transfer of low frequency noise (such as traffic rumble) into the induction loop signal. 
     The inductive loop or each inductive loop has between 5 and 50 turns. The loop  12  may be formed particularly conveniently from a length of flat ribbon cable of the type which is conventionally used to interconnect computer equipment and the like. Referring to FIG. 3, a length of ribbon cable  24  with individual conductors  26  may be joined end to end via a connector block  28  with the individual conductors  26  offset by one pitch, thus forming a multi-turn loop with inlet  30  and outlet  32 . 
     We have found that, surprisingly, a ribbon cable of between 10 and 20 conductors forms a loop which provides high quality signals to hearing aid induction pick-ups, and does so even when the loop is in close proximity to metal, such as the bodywork of a motor car. In such an application, a driving current of between 12 and 55 milliamps is required; with a ten way cable driving currents of 20-25 milliamps has been found to provide an acceptable signal. 
     The embodiment described provides a useable signal for a distance of some 7 to 8 feet, with the signal concentrated forwardly and rearwardly from the plane of the loop through an angle of about 45° to an axis transverse to the plane of the loop. This ensures that the enhancement is available to the hard of hearing person when the two participants in the conversation are in all normal conversational positions, but provide a high degree of privacy against other hearing aid users relatively nearby. 
     FIG. 4 illustrates a modified version of the foregoing embodiment in which the induction loop is incorporated within a waist belt  34  which is releasably closable by a buckle assembly  36 . The buckle assembly  36  has a first part  38  containing the power supply and the amplifier, and a second part  40 , these two being connectable by a tongue and slot arrangement which acts as a circuit connector and also activates an on/off switch. The first part  38  incorporates an interchangeable battery pack  40  which may be removed for recharging; nickel/metal hydride batteries are preferred, but lead/acid batteries may also be used. With the embodiment of FIG. 4, it would be preferred to use a microphone, as indicated at  42 , which can be positioned by the user to achieve best results, for example on the lapel. 
     As shown in FIG. 5, the belt  34  contains two induction coils  12   a  and  12   b  which may be selected alternately by the user by a switch  46 . The coils  12   a ,  12   b  are of differing numbers of turns. In one form, the first coil  12   a  has ten turns of insulated wire and the second coil  12   b  has twenty turns of insulated wire. This gives a choice of effective range of approximately 1 m and about 2-3 m, respectively, dependent on the degree of privacy desired. 
     The same effect could be achieved by using a single loop and connecting a switch such as  46  to set the gain of the amplifier either high or low. 
     The belt  34  may comprise an induction loop within any suitable decorative cover, for example, of leather or fabric. A section of the belt may be looped in an S-shape and provided with a sliding clasp, to provide adjustment of girth. In the embodiment of FIG. 2, the flexible loop  12  may equally be encased within a decorative cover, for example, a cloth sash printed with a suitable legend. 
     The apparatus of the present invention is primarily intended for wear by a professional person (for example, a medical attendant or a bank official) conducting business with a hard-of-hearing client. It may, however, be used in other ways. It may be worn by the hard of hearing themselves, as it produces superior performance in some situations to the conventional hearing aid alone. The apparatus also has the great benefit of allowing the hard-of-hearing person to hear his own voice, and thus to modulate his voice to suit the circumstances. 
     The basic unit (such as  38  in FIG. 4) may also be used off the person, such as by being placed on a table or hung on a wall. In this mode, it may be used with the same induction loop (such as  34  in FIG. 4) or alternatively by connected to another induction loop such as a fixed peripheral loop in a room, and for this purpose the basic unit and the induction loop are suitably interconnected by a plug and socket arrangement. 
     Other modifications and improvements may be made to the foregoing within the scope of the present invention, as defined in the claims.