U.S. patent number 3,875,349 [Application Number 05/326,550] was granted by the patent office on 1975-04-01 for hearing aid.
This patent grant is currently assigned to Bommer AG. Invention is credited to Heinz Ruegg.
United States Patent |
3,875,349 |
Ruegg |
April 1, 1975 |
Hearing aid
Abstract
A hearing aid for the hard of hearing incorporating a microphone
system connected with an amplifier. The microphone system embodies
a first microphone with approximately spherical-shaped sensitivity
characteristics and a second microphone with directional
sensitivity characteristics. The amplifier can be selectively
connected with one or the other of both microphones.
Inventors: |
Ruegg; Heinz (Thalwil,
CH) |
Assignee: |
Bommer AG (Zurich,
CH)
|
Family
ID: |
4212963 |
Appl.
No.: |
05/326,550 |
Filed: |
January 24, 1973 |
Foreign Application Priority Data
Current U.S.
Class: |
381/313;
381/123 |
Current CPC
Class: |
H03F
3/183 (20130101); H04R 25/402 (20130101); H04R
25/456 (20130101) |
Current International
Class: |
H03F
3/183 (20060101); H03F 3/181 (20060101); H04R
25/00 (20060101); H04r 025/00 () |
Field of
Search: |
;179/17R,17BC,17E,17H,17S,179,180,178,121D,1DM,17FD ;181/23 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
238,890 |
|
Sep 1926 |
|
UK |
|
1,512,667 |
|
Jun 1969 |
|
DT |
|
Primary Examiner: Blakeslee; Ralph D.
Attorney, Agent or Firm: Craig & Antonelli
Claims
What is claimed is:
1. An individual hearing aid for wearing by the hard of hearing,
the hearing aid being transportable by the wearer and comprising
amplifier means, a microphone system electrically coupled with said
amplifier means, said microphone system comprising a first
microphone having approximately spherical sensitivity
chatacteristics and a second microphone with directed sensitivity
characteristics, and means for selectively connecting the amplifier
means with one or the other of both microphones.
2. A hearing aid for the hard of hearing comprising amplifier
means, a microphone system electrically coupled with said amplifier
means, said microphone system comprising a first microphone having
approximately spherical sensitivity characteristics and a second
microphone with directed sensitivity characteristics, means for
selectively connecting the amplifier means with one or the other of
both microphones, and further including a housing, a partition wall
for subdividing the housing into two compartments, each of the
microphones being arranged in a respective compartment of the
housing, means defining a sound inlet opening which opens into one
of the compartments and means defining two oppositely situated
sound inlet openings opening into the other compartment.
3. The hearing aid as defined in claim 2, wherein each of the
microphones has a diaphragm which can be placed into oscillation,
and wherein said diaphragms are arranged substantially parallel to
the partition wall.
4. The hearing aid as defined in claim 3, wherein for said other
compartment one sound inlet opening is arranged at one side of the
diaphragm which can be oscillated and the other sound inlet opening
is arranged at the other side of said diaphragm of the associated
microphone.
5. The hearing aid as defined in claim 4, wherein the sound inlet
opening of said one compartment and said one sound inlet opening of
the other compartment communicate with a common sound inlet
funnel.
6. The hearing aid as defined in claim 5, wherein said other sound
inlet opening possesses a greater sound absorption capacity than
the remaining sound inlet openings.
7. The hearing aid as defined in claim 6, wherein both microphones
are connected via a controlled reversing switch means with a
threshold value amplifier constituting said amplifier means, and
said threshold value amplifier upon exceeding a predetermined
signal peak controls the reversing switch means for switching to
said second microphone.
8. The hearing aid as defined in claim 1, wherein both microphones
are connected via a controlled reversing switch means with a
threshold value amplifier constituting said amplifier means, said
threshold value amplifier upon exceeding a predetermined signal
peak controlling the reversing switch means for switching from one
of the microphones to the other of the microphones.
9. The hearing aid as defined in claim 8, wherein the reversing
switch means normally connects the first microphone with said
threshold value amplifier and in response to said threshold value
amplifier exceeding a predetermined signal peak connects the second
microphone to said amplifier.
10. The hearing aid as defined in claim 1, wherein the hearing aid
is a self-contained unit arranged for accommodation on the
wearer.
11. The hearing aid as defined in claim 1, further comprising
common housing means for accommodating at least the first and
second microphones for positioning on the wearer.
12. The hearing aid as defined in claim 11, wherein said amplifier
means is contained in said housing means.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a new and improved construction of
hearing aid for the hard of hearing of the type incorporating a
microphone system coupled with an amplifier. In the context of this
disclosure the expression "hearing aid" or "hearing device," or
equivalent terminology, should be understood as encompassing both
the so-called "behind-the-ear" as well as also the so-called
"in-the-ear" hearing aid and hearing aid eyeglasses, in other words
all hearing aids worn at or about the head of the user.
It is well known in this particular field of technology to equip
such hearing aids with microphones which possess a pronounced
directional characteristic. With such hearing aids the sound waves
which arrive from a predetermined direction are amplified and
transmitted to the wearer of the hearing aid, this direction, as a
general rule, coinciding with the line of sight or viewing
direction of the wearer. Although such hearing aids provide
adequate aid to the user during normal conversation with another
person, they are not totally satisfactory in an environment of use
where the sound emanates from all directions, since the user
becomes unsure of himself. It has been particularly determined that
people who are hard of hearing and who wear a hearing aid having a
microphone exhibiting directional sensitivity characteristics
become extremely unsure of themselves in traffic because, from the
entire background of sounds, they are only able to perceive those
sounds which coincide with their momentary line of sight.
On the other hand, there are known to the art hearing aids of the
previously mentioned type in which the microphone possesses a
so-called spherical sensitivity characteristic. Also such
constructions of hearing aids do not satisfy all of the needs of
the hard of hearing. Thus, for instance, a conversation with
another person is only possible for the person who is hard of
hearing when using such hearing aid if the party to whom the hard
of hearing person speaks raises his voice above the general sound
level of the surroundings, or then when the person who is hard of
hearing, in addition to listening to the sounds of the words of the
speaking person also lip reads.
SUMMARY OF THE INVENTION
Hence, it is a primary object of the present invention to provide
an improved construction of hearing aid which is capable of
reliably fulfilling the needs of the hard of hearing practically
for all encountered situations.
A further object of the present invention relates to an improved
construction of hearing aid which combines the advantages of a
hearing aid equipped with a microphone having directional
characteristics with a hearing aid equipped with a microphone
having spherical sensitivity characteristics while avoiding the
drawbacks present when only using a microphone in a hearing aid
having one or the other of such sensitivity characteristics.
Now in order to implement these and still further objects of the
invention, which will become more readily apparent as the
description proceeds, the proposed hearing aid is manifested by the
features that the microphone system possesses a first microphone
having spherical sensitivity characteristics and a second
microphone with directional sensitivity characteristics, and
wherein the amplifier can be selectively switched to either one of
both microphones.
Thus, a minature hand-operated reversing switch can be provided
between the microphones and the amplifier, and which switch can be
actuated, when required, by the user without having to remove the
hearing aid. On the other hand, both of the microphones can be
arranged through the agency of a controlled reversing switch
following a threshold value amplifier, which upon exceeding a
predetermied signal peak controls the reversing switch for
switching to the second microphone, that is to say, to that
microphone which has a pronounced directional characteristic. This
predetermined signal peak can be set to a value which occurs when
the wearer is carrying out a conversation with another person at a
normal distance.
Both of the microphones are preferably each arranged in a
respective compartment of a housing subdivided by a partition wall
into two compartments or chambers, wherein in the first compartment
there opens a sound inlet opening and in the second compartment two
oppositely situated sound inlet openings. In order to avoid
acoustical feedback it is advantageous to arrange the diaphragms or
membranes of the microphones and which are capable of vibrating or
oscillating such that they are each essentially parallel to the
partition wall. For further avoiding acoustical feedback there can
be arranged at the second compartment the one sound inlet opening
at one side of the vibratable diaphragm and the other sound inlet
opening at the other side thereof of the associated microphone.
Moreover, the directional characteristics of the second microphone
can be increased if the one sound inlet opening associated with
such microphone possesses a greater sound absorption capacity than
the other sound inlet opening.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood and objects other than
those set forth above, will become apparent when consideration is
given to the following detailed description thereof. Such
description makes reference to the annexed drawings wherein:
FIG. 1 is a simplified block circuit diagram of a hearing aid which
can be manually switched;
FIG. 2 is a simplified block circuit diagram of a hearing aid which
can be automatically switched;
FIG. 3 schematically illustrates the sensitivity characteristics of
a first microphone;
FIG. 4 schematically illustrates the sensitivity characteristics of
a second microphone; and
FIG. 5 is a circuit diagram of a hearing aid equipped with
manually-switchable microphones, wherein the arrangement of both
microphones is illustrated in a common housing.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Describing now the drawings, the hearing aid 10, depicted by way of
example in FIG. 1, possesses two microphones 11 and 12, wherein the
first microphone, the microphone 11, as will be understood by
referring to FIG. 3, is assumed to possess a spherical-type of
sensitivity characteristic, whereas the second microphone, the
microphone 12, as indicated in FIG. 4, is assumed to possess a
sensitivity having a pronounced directional characteristic. The
microphone 11 is electrically coupled via a conductor or line 13
with one fixed contact 15 and the microphone 12 via a conductor or
line 14 with the other fixed contact 16 of a reversing switch or
switch means 22. The movable contact 17 of the reversing switch 22
is connected through the agency of a conductor 18 with an amplifier
19. The output of amplifier 19 is connected via a conductor 20 with
an electro-mechanical transducer, for instance a loud-speaker 21
where the electrical signals emanating from the microphone 11 or
the microphone 12 are amplified by amplifier 19, and again
transformed into mechanical oscillations, that is to say, sound
waves.
The same elements will be also recognized to be present with the
constructional embodiment of FIG. 2, wherein, however, in this
case, instead of the reversing switch 22 there is employed an
automatically controlled electronic reversing switch 23. In this
embodiment the amplifier 19 is a so-called threshold value
amplifier which, apart from the output or output conductor 20 which
leads to the loudspeaker 21, possesses a second output 24 where
there then appears a signal when the signal prevailing from one of
both microphones 11 and 12 exceeds a predetermined signal peak. The
output 24 is connected through the agency of a further switching
element, designated by reference character 25, with the control
input 26 of the reversing switch or switch means 23. The switch
element 25 can be a control or regulator, but also can be a
frequency-dependent discriminator stage, so that switching-over to
the microphone 12 possessing the pronounced directional
characteristic, not only then occurs when a sound has assumed a
predetermined intensity, rather when such sound also possesses a
predetermined frequency spectrum. Switching back to the microphone
11 possessing the spherical sensitivity characteristic can occur
both automatically upon the absence of a signal at the amplifier
output 24, or also however manually, so that the user has the
possibility of intentionally controlling the hearing aid.
It is to be observed that both in the embodiment of FIG. 1 as also
in the embodiment of FIG. 2 the microphones can be
electro-magnetic, piezo-electrical or dielectrical microphones
wherein, however, both microphones always will be of the same type
owing to the nature of the different frequency characteristics.
Also the amplifiers of both embodiments can be linear, AGC
(automatic gain control) or non-linear controlled amplifiers.
Now in FIG. 5 there is illustrated a detailed circuit diagram of
hearing aid with the two schematically arranged microphones of such
hearing aid collectively accommodated in a single housing.
Initially on the basis of the discussion of FIG. 5 there will be
considered the construction of the microphone system. Both of the
microphones 11 and 12 are arranged in a common housing 27, the
internal compartment of which is subdivided into two compartments
or chambers 29 and 30 by a partition wall 28. In the compartment 29
there is arranged the microphone 11 with its diaphragm or membrane
38 and its transducer component 39, while in the compartment 30
there is arranged the microphone 12 with its diaphragm or membrane
40 and its transducer component 41. The compartment 29 possesses a
sound inlet opening 31 which, as best seen by referring to FIG. 5,
opens into the compartment 29 at the side or face of the diaphragm
38 facing away from the transducer component 39. On the other hand,
the compartment 30 possesses two oppositely situated sound inlet
openings 32 and 35, wherein the sound inlet opening 32 opens into
the compartment 30 at the side of the diaphragm 40 which faces away
from the transducer component 41 and the sound inlet opening 35
opens at the side of the diaphragm 40 which confronts the
transducer component 41.
A common sound inlet funnel 33 is arranged forwardly of both sound
inlet openings 31 and 32. The sound inlet funnel 33 possesses a
single inlet opening 34. On the other hand, connected in front of
the sound inlet opening 35 is a stud or connection piece 36 having
an opening 37. The arrangement is carried out such that the sound
absorption capacity of the inlet locations formed by the openings
35, 37 and the stud 36 is greater than the sound absorption
capacity of the inlet location formed by the openings 31, 32 and 34
as well as the funnel 33.
Now if this arrangement is subjected to sound vibrations or
oscillations, then initially the entire outside of the housing 27
will be uniformly impinged by the sound pressure, something which
for itself will not have any effect upon the microphone 11 and 12.
The parts of the compartments 29 and 30 which are located, on the
one hand, between the partition wall 28 and, on the other hand, the
respective diaphragms 38 and 40 will be subjected to the action of
the sound pressure which enters via the openings 31 and 32. The
partition wall 28 will therefore so to speak be impinged in a
push-pull mode from both sides by the sound oscillations or
vibrations, so that as a practical matter it does not begin to
vibrate or oscillate, whereby there is practically eliminated the
possibility of acoustical feedback between the compartments 29 and
30. Since the microphone 11 only has associated therewith one sound
inlet opening, namely the opening 31, the diaphragm 38 will be
activated by all of the oscillations which enter through such
opening, independently of the direction in which such arrive at the
funnel opening 34 and therefore at the sound inlet opening 31.
Hence the microphone 11, insofar as its receiving sensitivity is
concerned, possesses a spherical-type characteristic as same has
been schematically depicted in FIG. 3. The conditions are different
for the microphone 12. In this case both sides of the diaphragm or
membrane 40 are impinged by the sound pressure, wherein, however,
the sound waves which enter the opening 35 are dampened to a
greater extent than the sound waves which enter through the opening
32. Consequently, the diaphragm 40 is placed into oscillation
which, however, is only predicated upon the magnitude of the
pressure differential in the compartment 30 which prevails between
both faces or sides of the diaphragm 40. Since additionally the
sound inlet openings 32 and 35 are arranged opposite one another
the microphone 12 possesses, as concerns its receiving sensitivity,
a pronounced directional characteristic, and specifically such
microphone possesses in the position depicted in FIG. 5 a
considerably greater sensitivity for sound waves which emanate from
the left than for those which can enter from the right through the
opening 35.
Both of the microphones 11 and 12 are each coupled through the
agency of the conductor lines 13 and 14 respectively, with the
reversing switch 22 and the amplifier 19. At such conductor lines
13 and 14 there is shown in phantom lines a supply conductor for
the situation where the microphones 11 and 12 are of the type
belonging to the class of piezo-electrical or dielectrical
microphones. The illustrated amplifier 19 is a conventional
miniaturized hearing aid-amplifier. The power supply to such
amplifier 19 takes place through the agency of a suitable and
therefore not particularly illustrated current source coupled with
the terminals 45 and 46, wherein an installed switch 44 serves to
switch-on the amplifier 19. The weak tone-frequency signal which
emanates from one of the microphones 11 and 12, depending upon the
position of the reversing switch 22, is delivered to the amplifier
19 through the agency of the input terminal 43. Amplifier 19 is
composed of the resistors R1-R6, the capacitors C1-C7, the
transistors T1-T3 as well as the potentiometer Rv serving as the
loud-speaker control and the variable resistor Rt1. A non-linear
network is arranged in circuit with the conductor 47 leading to the
loud-speaker 21, and this non-linear network consists of the
resistor R7, both of the diodes D1 and D2 which are arranged in an
anti-parallel circuit configuration and the variable resistor Rt2.
This network produces a non-linear alternating-current feedback
which, in turn, produces an amplification- or output-dependent,
approximately logarithmic feedback or output limiting effect.
It should be understood that those skilled in the art will have
considerable leeway as concerns the construction of the amplifier.
Purely by way of example it is mentioned that the circuit
components enclosed by the phantom-line box 42 can be constructed
as an integrated circuit, at which there are coupled the adjustable
or regulatable switching elements, namely the switch 44, the
potentiometer Rv as well as the variable resistors Rt1 and Rt2. It
is, however, also possible to provide, instead of the illustrated
amplifier 19, a linear-amplifying amplifier which is controlled by
a DC-voltage or limited by so-called "peak clipping," and which
constitutes electrical hardware particularly well known to those
skilled in the hearing aid art.
While there is shown and described present preferred embodiments of
the invention, it is to be distinctly understood that the invention
is not limited thereto, but may be otherwise variously embodied and
practiced within the scope of the following claims.
Accordingly,
* * * * *