[0001] The present invention relates to hearing aids and, more particularly, to touch contacts
for use in controlling the volume of a hearing aid.
[0002] Hearing aids are miniaturized devices generally placed in or behind the ear and are
used to amplify sounds for the hearing impaired. Hearing aids include some means of
volume control to allow battery life to be extended and to allow for comfortable listening
levels by the user.
[0003] Conventionally, the volume control has been a variable resistor or potentiometer
and is mounted to a plate or face plate on the hearing aid so that a knob or screw
adjuster attached to the wiper arm of the variable resistor is used to change the
resistance and thereby change the amplification levels of the hearing aid. Given the
small sizes of hearing aids, particularly in-the-ear hearing aids, this knob or screw
adjuster used for volume control is very small and very hard to use, particularly
for users which also have decreased sensitivity and dexterity. It is desirable to
have a hearing aid volume control which is easier to use than the very small knobs
conventionally used with variable resistors.
[0004] A touch sensitive hearing aid was disclosed in U.S. patent 4,679,240, by this inventor.
The design uses at least three separate contacts for use with a touch sensitive volume
control circuit. One contact is used in combination with the common contact to signify
a desired increase in the volume, while a second contact is used in combination with
the common contact to signify a decrease in the desired volume or amplification levels
of the hearing aid. While this design improved over the use of the knobs and variable
resistors of previous designs, the use of three or four touch contacts required a
minimum physical spacing on the hearing aid, which for hearing aids of different or
smaller configurations is difficult to obtain.
[0005] Therefore it is desirable to have a method of volume control of a hearing aid which
is touch sensitive, requires less surface area than the one in the referenced patent
and is easy to locate with the tip of a finger in the confined space and location
of a hearing aid.
[0006] The touch contacts of an embodiment of the present invention are adapted to be placed
in a small environment and yet be readily accessible by the finger of the user to
allow ease in changing the volume of the hearing aid. The circuitry of the hearing
aid is designed to require the use of only two touch sensitive contacts for allowing
volume changes of the hearing aid. Touching the two contacts a first time and holding
the contacts increases the volume, while touching the contacts a second time and holding
the contacts results in a decrease in the volume of the hearing aid.
[0007] The touch contacts are preferably located adjacent a battery door of the hearing
aid. The battery door commonly has located adjacent to it guides or guide lips which
extend past the battery door, the guides thereby forming the most prominent portion
of the hearing aid. The touch contacts are preferably formed of gold-plated wire
which is placed along the edge of each guide, thereby placing the touch contacts in
the most prominent position of the hearing aid and yet not requiring additional space
on the face plate or cover of the hearing aid. The user merely touches the face plate
of the hearing aid, which generally results in the touching of the battery door and
adjacent guides. Since the face plate is usually the most prominent and accessible
portion of the hearing aid, the two contacts are easy to touch to effect the appropriate
and desired volume change.
[0008] A better understanding of the invention can be obtained when the detailed description
of the exemplary embodiment set forth below is considered in conjunction with the
following drawings, in which:
Figure 1 is a perspective view of an embodiment of a hearing aid incorporating the
touch contacts according to the present invention;
Figure 2 is a top view of an embodiment of a face plate containing touch contacts
according to the present invention;
Figure 3 is an enlarged view of portions of Figure 2;
Figure 4 is a partial side view of an embodiment of a face plate and battery housing
including touch contacts according to the present invention; and
Figure 5 is an embodiment of an electrical block diagram of the circuitry of a hearing
aid having touch contacts according to the present invention.
[0009] Referring to Figure 1, an embodiment of a hearing aid in accordance with the present
invention is generally designated by the letter H. The hearing aid H contains a housing
portion 10 which is adapted to be inserted in an ear canal (not shown) and perform
the function of an in-the-ear hearing aid. A face plate 12 forms the portion of the
hearing aid H which is visible or accessible when the hearing aid H is installed in
the ear. A microphone port 14 is formed in the face plate 12 for allowing sound to
be transmitted to a microphone 40 (Fig. 5) contained in the housing 10. A battery
door 16 is pivotally connected to the face plate 12 and opens in the direction of
arrow A to allow removal, changing or insertion of a battery 42 that is necessary
for the hearing aid circuitry to function. A pair of battery guides 18 project from
the outer surface of the face plate 12 and are located adjacent to the battery door
16 and perpendicular to the face plate 12. The guides 18 effectively provide and form
sides to the battery door 16 and hold the battery 42 in place as the door 16 opens
and closes. A pair of touch contact wires 20, described in greater detail below, are
positioned on the edge of the guides 18.
[0010] Fig. 2 shows a face plate assembly F having a battery door 16 installed on an uncut
face plate 22. The face plate assembly F initially starts out as a large round disk
on which the battery door 16 and the guides 18 are installed. A face plate assembly
of this type is available commercially from sources known to those skilled in the
art. The touch contact wires 20 are then added. The face plate 22 is cut by the hearing
aid manufacturer to form the face plate 12 shown in Fig. 1, which is attached to the
housing 10 of the hearing aid H.
[0011] The guides 18 include hinge assemblies 24 (Fig. 3), which allow the battery door
16 to pivot away from the face plate 22 in the direction of the arrow A (Fig. 1) and
allow easy changing of the battery 42. The guides 18 have a discrete thickness and
are formed perpendicular to the face plate 22 to form sides of the battery door 16.
This structure allows the battery door 16 to project above the face plate 22 a short
distance so that the door 16 can easily be opened and closed by grasping a handle
portion 19. Terminals 28 (Fig. 4) for contacting the battery 42 so that power can
be supplied to the circuitry of Fig. 5 are located beneath the face plate 12 in the
hearing aid H.
[0012] The touch contact wires 20 are installed along the outer edges of the guides 18 and
enter the body of the hearing aid H through holes 26 formed in the face plate 22.
Since the guides 18 project above the battery door 16 (Fig. 4), the touch contact
wires 20 are located at the most prominent portion of the hearing aid H. This location
allows the user to touch both of the touch contact wires 20 easily, thereby allowing
the hearing aid amplification circuitry C to sense the touch of a finger for changing
the volume as described below.
[0013] The amplification circuitry C (Fig. 5) is adapted for use with two touch contact
wires 20. Sound waves are received by a microphone 40, which produces an output signal
100. The microphone output signal 100 is filtered by a capacitor 102 to remove any
direct current components of the signal 100 and is provided to the input 104 of a
first class A amplifier 106. A series combination of two resistors 110, 112 is connected
from the output 108 to the input 104 of the amplifier 106 to set portions of the feedback
resistance and therefore gain of the amplifier 106.
[0014] Connected across one of the resistors 110 are the output terminals 116 of a programmable
transconductance block 114. The output terminals 116 are connected to a controlled
resistance internal to the transconductance block 114. The transconductance block
114 uses a capacitor 118 connected to ground to set an oscillator frequency. Additionally,
the transconductance block 114 is connected to each of the touch contact wires 20.
The transconductance block 114 varies the resistance developed between the output
terminals 116 based on touches of the touch contact wires 20. Touching the touch contact
wires 20 a first time causes the effective output resistance, and therefore amplifier
106 gain, to increase as the contact is maintained, at a rate based on the oscillator
frequency. Touching the touch contact wires 20 a second time causes the effective
output resistance, and therefore the amplifier 106 gain, to decrease as the contact
is maintained. Repeated contacts of the touch contact wires 20 cause the resistance
to change in an alternating manner as described.
[0015] The output terminals 116 of the transconductance block 114 are connected across the
resistor 110 so that minimum and maximum gains of the amplifier 106 are set by the
fixed resistors 110, 112 and damage to the hearing of the user is prevented, while
at the same time not allowing the gain to go below a minimum usable amount and allowing
the gain to be varied between the minimum and maximum amounts.
[0016] The output 108 of the first amplifier 106 is connected to the input 120 of a second
class A amplifier 122. The second amplifier 122 is configured in a fixed gain arrangement
through the use of two resistors 124, 126 connected to the amplifier 122. A speaker
or receiver 46 is connected to the output 128 of the amplifier 122 and to the positive
supply to provide a means for converting the amplified signal back into sound waves
for transmission to the user's middle ear structure.
[0017] The touch contact wires 20 are preferably gold-plated for improved sensitivity and
lack of corrosion. However, other conductive materials, such as silver or copper,
would be suitable for this purpose. The wires 20 are affixed to the guides 18 by suitable
adhesive means.
[0018] While the embodiment shown and described above uses a battery door 16 designed for
a battery 42 which is inserted having its axis parallel to the plane of the face plate
12, it is understood that touch contact wires 20 can also be used with a hearing aid
H having a battery door adapted for placement of the battery with the battery axis
perpendicular to the plane of the face plate 12 and on other battery arrangements
and battery door configurations which have been and can be developed.
[0019] The foregoing disclosure and description of the invention are illustrative and explanatory
of the invention, and various changes in the size, shape, and materials, as well as
in details of the illustrated construction may be made without departing from the
spirit of the invention, all of which are contemplated as falling within the scope
of the appended claims.
1. A hearing aid, comprising:
a housing, which includes a face plate adapted to be accessible when the hearing aid
is installed in an ear canal;
a battery door located in said face plate for allowing a battery to be inserted into
and removed from the hearing aid; and
circuit means in the housing for receiving and amplifying sound, said circuit means
including two touch contacts for use in controlling the amplification level of the
sound;
said touch contacts being located directly adjacent to and on opposite sides of said
battery door on the accessible side of said face plate.
2. The hearing aid of Claim 1, wherein the battery door is adapted for insertion or
removal of a battery whose axis is parallel to the plane of said face plate.
3. The hearing aid of Claim 2, further comprising:
flat guides perpendicular to said face plate and perpendicular to the battery axis
and located adjacent to said battery door so as to provide sides to said battery door.
4. The hearing aid of Claim 3, wherein said touch contacts are located on the edge
of said guides away from said face plate.
5. The hearing aid of Claim 4, wherein said guide edges extend farther from said face
plate than said battery door.
6. The hearing aid of any one of the preceding claims, wherein said touch contacts
are formed of gold-plated wire.