U.S. patent number 3,909,556 [Application Number 05/495,837] was granted by the patent office on 1975-09-30 for directionally variable hearing aid.
This patent grant is currently assigned to Audivox, Inc.. Invention is credited to Donald L. Johanson.
United States Patent |
3,909,556 |
Johanson |
September 30, 1975 |
Directionally variable hearing aid
Abstract
A hearing aid in which the sound reception characteristics are
selectable by a user to provide non-directional or directional
reception, as desired. The hearing aid employs a differential
transducer having two sound receiving ports and operative to
convert sound information into an electrical output and to which
sound energy can be directed in one of two modes. In one mode of
operation, for providing non-directional reception, sound is
received from a front aperture of the hearing aid and directed to
first and second input ports of the transducer, the sound being
directed to the second port via an acoustic filter. In a second
mode of operation, for providing directional reception, the second
input port of the transducer is coupled to a rear aperture of the
hearing aid and the first input port remains coupled to the front
aperture. Sound energy received from the rear of the hearing aid is
substantially minimized by action of the transducer without
affecting energy from the front of the hearing aid. The acoustic
filter in the second transducer port path during non-directional
operation is used to match the frequency and phase characteristics
of the non-directional mode response to the frequency and phase
characteristics of the directional mode frontal response so that
switching from one mode to another does not materially alter the
quality of sound reception from the front direction of the hearing
aid.
Inventors: |
Johanson; Donald L. (Wayland,
MA) |
Assignee: |
Audivox, Inc. (Newton,
MA)
|
Family
ID: |
23970180 |
Appl.
No.: |
05/495,837 |
Filed: |
August 8, 1974 |
Current U.S.
Class: |
381/313; 381/330;
381/387 |
Current CPC
Class: |
H04R
1/38 (20130101); H04R 25/402 (20130101); H04R
2225/61 (20130101); H04R 25/603 (20190501) |
Current International
Class: |
H04R
25/00 (20060101); H04R 1/38 (20060101); H04R
1/32 (20060101); H04R 025/00 () |
Field of
Search: |
;179/17FD |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Blakeslee; Ralph D.
Attorney, Agent or Firm: Weingarten, Maxham &
Schurgin
Claims
What is claimed is:
1. A hearing aid comprising:
a differential transducer having first and second sound receiving
ports;
a housing having a forwardly facing sound receiving aperture and a
rearwardly facing sound receiving aperture;
a first sound receiving path between said forwardly facing aperture
and said first transducer port;
a second sound receiving path distinct from said first sound
receiving path for selectively coupling said second receiving port
to said first or second sound receiving apertures and including
control valve means operative in a first position to couple sound
energy received by said rearwardly facing aperture to said second
sound receiving port, and in a second position to couple sound
energy received by said forwardly facing aperture to said second
sound receiving port;
acoustic filter means in said second sound receiving path only when
said valve means is in said second position;
electronic circuitry for amplifying and processing sound
information received by said transducer; and
an earpiece coupled to said circuitry and adapted to the ear of a
user.
2. A hearing aid according to claim 1 wherein
said first sound receiving path includes a first passage between
said forwardly facing aperture and said valve means, and a second
passage between said first passage and said first transducer port;
and
said second sound receiving path includes said first passage and a
third passage between said rearwardly facing aperture and said
valve means, and a fourth passage between said valve means and said
second transducer port;
said valve means being operative in its first position to provide a
sound receiving path through said third and fourth passages, and
operative in its second position to provide a sound receiving path
through said first and fourth passages.
3. A hearing aid according to claim 2 wherein said valve means
includes
a rotatable member disposed at the juncture of said first, third
and fourth passages and having an opening therethrough for coupling
said third and fourth passages in said first position, and for
coupling said first and fourth passages in said second position;
and
a manually actuable control knob attached to said rotatable member
and operative to rotate said member between said first and second
positions.
4. A hearing aid according to claim 3 wherein said filter means is
in said rotatable valve member.
5. In a hearing aid having a predetermined directional mode
response and a selectably operable predetermined non-directional
mode response and including:
a housing having a forwardly facing sound receiving aperture and a
rearwardly facing sound receiving aperture;
a differential transducer in the housing having first and second
sound receiving ports;
a network of sound conducting passages in the housing connecting
the apertures to the ports; and
a valve means for selectably coupling the rear transducer port to
either the front or rear aperture;
the improvement comprising:
a sound conducting passage containing an acoustic filter for
selectively varying the frequency and phase characteristics of
received sound only when said rear transducer port is coupled by
said valve means to said front aperture of said housing;
whereby the frequency and phase characteristics of sound energy
emanating from the front of the wearer are not materially altered
when the aid is switched from one mode to to the other.
6. A hearing aid comprising:
a housing;
a differential transducer within said housing having first and
second sound receiving ports;
a channel in said housing extending between a front sound aperture
and a rear sound aperture;
a first sound passage coupled from said channel to said first port
of the transducer;
a second sound passage coupled from said channel to said second
port of the transducer;
valve means at the intersection of said channel and said second
passage operative in a first position to couple said second port of
said transducer to said rear aperture and operable in a second
position to couple said second port of the transducer to said front
aperture;
an acoustic filter disposed in said channel between said first and
second passages;
means operative in response to the signal output of said transducer
for providing an output signal suitable for coupling to the ear of
a user.
7. A hearing aid adapted to be disposed in the temple of an
eyeglass frame and comprising:
a differential transducer having first and second sound receiving
ports;
a first receiving aperture in the temple of said eyeglass frame
forward of the ear position of a user;
a second sound receiving aperture in said temple of said eyeglass
frame forward of the ear position of a user and rearward of the
first sound receiving aperture;
a first physically distinct sound receiving path between said
forward aperture and said first transducer port;
a second physically distinct sound receiving path for selectively
coupling said second receiving port to said first or second sound
receiving apertures and including
control valve means operative in a first position to couple sound
energy received by said rearward aperture to said second sound
receiving port, and in a second position to couple sound energy
received by said forward aperture to said second sound receiving
port;
acoustic filter means coupled to said second receiving path only
when the valve means is in said second position;
electronic circuitry for amplifying and processing sound
information received by said transducer; and
an earpiece coupled to said circuitry and adapted to the ear of a
user.
Description
FIELD OF THE INVENTION
The invention relates to hearing aids and more particularly to a
hearing aid adjustable by a user to selectively provide
non-directional or directional receiving characteristics.
BACKGROUND OF THE INVENTION
It is usually desirable that a hearing aid provide good
non-directional response to sounds emanating from points to the
front, rear and sides of a user. A particularly effective
multidirectional hearing aid is described in U.S. Pat. No.
3,201,528, assigned to the assignee of the present invention,
wherein both forward facing and rearward facing receiving apertures
are provided to direct received sound information to a microphone
and to provide substantially uniform gain for sounds emanating from
various points about the user. In many instances however, such as
in listening to lectures, conversations in a noisy environment, and
the like, it would be desirable to enhance the directional
characteristics of the hearing aid to accentuate the gain of sounds
emanating forwardly of the user. Because of different needs in
different listening situations, it is useful to provide a
capability of both non-directional and directional characteristics
in one hearing aid. A particularly effective selectable directional
hearing aid is described in copending U.S. patent application Ser.
No. 286,577, filed Sept. 7, 1972, assigned to the assignee of the
present invention.
The invention described in the aforesaid patent application attains
two modes of operation by selectively occluding the rear transducer
port. However, it has been found that closing the rear transducer
port can cause an excessive increase in low frequency gain,
resulting in a non-directional mode response characteristic
stronger in the low frequencies than the directional mode frontal
response. Ideally these response characteristics should be equal
particularly in a high gain hearing aid wherein excessive low
frequency gain can cause acoustical instability.
SUMMARY OF THE INVENTION
In accordance with the present invention a selectably directional
hearing aid is provided which can be operated, even at high gain
levels, without undesirable instability and, which can be switched
from one mode to another without materially altering the quality of
the received sound from the frontal direction. Undesirable
instability at high gain levels is avoided by keeping the rear
transducer port open during both non-directional and directional
modes of operation, and employing an acoustic filter in the path of
the sound energy received at the rear port in the non-directional
mode. The acoustic filter also serves to avoid undesirable material
alteration of sound quality, when the hearing aid is switched from
one mode to another, by selective enhancement of the low frequency
response of the hearing aid in the non-directional mode, so as to
approximate that of the directional mode.
The invention makes use of a differential transducer disposed
inside a housing adapted to be worn by the user, the housing having
a front and rear sound aperture. Disposed inside the housing are a
network of sound conducting paths connecting the apertures to the
transducer ports. The front aperture is always in sound
communication with the first transducer port. A valve means is
provided in the sound conducting paths, whereby the second port of
the transducer may be made to communicate either with the rear
aperture in the directional mode, or the front aperture in the
non-directional mode.
When the valve is in the directional mode position, sound entering
the front aperture is channelled to the first transducer port,
while sound entering the rear aperture is channelled to the second
transducer port. Sound emanating from points to the rear of a user
tend to be cancelled or substantially reduced in amplitude by
operation of the differential transducer, with the result that the
hearing aid is most sensitive to sound emanating from points
forward of the user and, thereby providing directional sound
response. With the valve in the non-directional mode position,
sound entering from the front aperture is channelled directly to
the first transducer port along one path and, through an acoustic
filter, to the second transducer port along a second path.
Switching of the second transducer port to the front aperture in
combination with the acoustic filter adjusts the sound energy
received at the second transducer port during the non-directional
mode to minimize rear port cancellation and to adjust the response
characteristics of the non-directional response to approximate that
of the directional front response.
The second transducer port is always in communication with a sound
receiving path and the transducer is not subject to instability
which can be caused under high gain conditions when the port is
occluded. Thus, the hearing aid of the present invention operates
well even at high gain levels and can be switched from a
directional to a non-directional mode of operation without
materially altering the relative quality of received sound.
The invention can be embodied in both a behind-the-ear type of
hearing aid or in an eyeglass frame type in which the hearing aid
is usually incorporated into the bow or temple of the frame.
DESCRIPTION OF THE DRAWINGS
The invention will be more fully understood from the following
detailed description taken in conjunction with the accompanying
drawings, in which:
FIG. 1 is a perspective view of a behind-the-ear type of hearing
aid according to the invention;
FIG. 2 is an enlarged elevation view of the embodiment of FIG.
1;
FIG. 3 is a partly cut away enlarged elevation view of a portion of
the structure of FIG. 2 with the control valve in a position
opposite to that shown in FIG. 2;
FIG. 4 is a pictorial view of the invention embodied in an eyeglass
type hearing aid;
FIG. 5 is a partly cut away enlarged elevation view of a portion of
the structure of FIG. 4; and
FIGS. 6-8 are diagrammatic representations of an alternative
embodiment of the valve assembly.
DETAILED DESCRIPTION OF THE INVENTION
The invention as embodied in a behind-the-ear type of hearing aid
is shown in FIG. 1 and includes a housing 10 adapted and configured
to be worn on the ear 12 (shown in phantom) of a user and coupled
by a length of tubing 14 to an earpiece 16 worn in the user's ear.
Included within housing 10 is a transducer for converting received
sound energy into corresponding electrical energy, amplifying and
processing circuitry, a battery source and volume and other
controls and a receiver for transducing the amplified electrical
signals into acoustical energy for conveyance via tubing 14 to the
earpiece 16. Alternatively, the earpiece can include the receiver
which is electrically energized via interconnecting wires from the
aid circuitry.
The housing 10 includes an upper portion 17 which extends above the
ear of a user and which contains an aperture 18 which is positioned
to receive sounds emanating from points forwardly of the user. A
rearwardly facing aperture 20, visible in FIGS. 2 and 3, is also
provided in the rear surface of upper portion 17 of housing 10 to
receive sounds from points rearwardly of the user. A manually
adjustable control valve 22 having a control knob 24 is provided in
the upper housing portion and is operative according to the
invention to alter the directional response characteristics of the
hearing aid.
Referring to FIG. 2, it is seen that frontwardly facing aperture 18
communicates with valve 22 via a longitudinal channel 26 provided
in the top portion of housing 10. Section 44 extends channel 26
from the valve 22 to the rear aperture 20. A differential
transducer 28 is contained within housing 10 and has a first port
30 coupled to a passage 32 which is in sound communication with
channel 26 at a position between aperture 18 and valve 22. A second
port 34 of transducer 28 is coupled via a tube 36 to valve 22 via a
passage 38.
An acoustic filter 50 having a cylindrical hole 51 therethrough, is
disposed in channel 26 between valve 22 and the intersection of
path 32 with channel 26.
The control valve 22 includes a cylinder 40 disposed within a
cylindrical recess formed transversely across housing 10 and in
which cylinder 40 is rotatable by action of a manual force applied
to control knob 24.
An opening 41 is provided through cylinder 40, and in one position,
depicted in FIG. 2, provides a sound communication path from rear
aperture 20 through the valve into passage 38, and thence via tube
36 to the second port 34 of transducer 28. With the valve 22
rotated to its second position, as depicted in FIG. 3, the passage
44 is occluded by the solid portion of cylinder 40, and a sound
communication path is provided to allow aperture 18 to communicate
with the first sound port 30 of transducer 28 through channel 26
and path 32 and with the second sound port 34 of transducer 28
through channel 26, filter 50, opening 41, path 38 and tube 36.
The transducer 28 is of the differential type in which sound energy
entering the second port 34 is subtracted from energy entering the
first port 30, such that the transducer is responsive to the
difference in received energy to provide a corresponding electrical
output signal. Such transducers, also known as unidirectional
microphones, are per se well known in the art, a typical example
being the directional microphone manufactured by Knowles
Electronics, Inc., Model BL-1687. Such a differential transducer is
also described in U.S. Pat. No. 3,770,911.
With the control valve in the position illustrated in FIG. 2,
sounds emanating from points rearwardly of a user enter the hearing
aid via aperture 20 and thence via passages 44, 38 and 36 to port
34. The transducer 28 and associated valve system is operative to
substantially cancel the effects of energy emanating from the rear
of aperture 20 and to provide an output signal which is essentially
representative of energy received by aperture 18 and resulting from
sounds from points forwardly of a user. The hearing aid in this
mode of operation is therefore directional and provides enhanced
reception for sounds in front of the user. In this mode the filter
50 is inoperative.
With control valve 22 in the position depicted in FIG. 3 the
hearing aid is in the non-directional mode. The port 34 of
transducer 28 communicates with aperture 18 through channel 26,
filter 50, path 38, opening 41 and tube 36. Port 30 of transducer
28 also communicates with aperture 18 through channel 26 and path
32. Thus for non-directional operation the rear aperture 20 is
occluded and the front aperture 18 is coupled to both ports 30 and
34 of transducer 28. The rear port is always open to received sound
and instability is avoided. In the non-directional mode the rear
port receives sound via a filter which operates to prevent rear
port cancellation in the transducer and to match phase and
frequency characteristics of the non-directional response to
approximate the directional front response. The hearing aid
operates well even at high gain levels and switching the hearing
aid from one mode to other does not materially alter the quality of
sound reception emanating from the front of the user.
In the illustrated embodiment, channel 26 between front aperture 18
and valve 22 is rectangular in cross-section with a height of
approximately .055 inches and a width of approximately 0.065
inches. Filter 50 fits securely in channel 26 and is approximately
0.060 inches long, with hole 51 therethrough approximately 0.016
inches in diameter. The filter 50 can be of any material and
configuration providing the acoustic impedance to achieve the
intended alteration of the frequency and phase characteristics of
received sound. The filter can employ an opening such as shown in
the illustrated embodiment, the cross-section and length of the
opening determining the filtering action. The filter can also be of
acoustically porous structure in which the volume and porosity
determine filtering action. It will be appreciated that the
acoustic filter can be formed as a separate element installed in
the hearing aid or formed integrally with the housing 10.
Alternatively, the filter can be provided at other locations in the
sound receiving path such as part of valve 22. As shown in FIG. 6,
valve cylinder 110 includes an opening 112 therethrough providing
the intended acoustic filtering according to the invention, and a
larger opening or slot 113. With the valve in a position to provide
non-directional operation (FIG. 7), opening 112 communicates
between passages 114 and 116 which are coupled respectively to the
front hearing aid aperture and the second transducer port. Passage
118 coupled to the rear aperture is occluded. With the valve in the
position providing directional operation (FIG. 8), passages 116 and
118 are interconnected via opening 113, with filter opening 112
being of no effect.
The directional receiving pattern of the hearing aid is essentially
cardioid in shape, as is usual for directional microphones, and the
particular pattern can be varied as desired by adjusting the
distance between apertures 18 and 20 to effectively vary the
pressure pattern on transducer ports 30 and 34.
The invention can also be embodied in hearing aids other than
behind-the-ear types; for example, the invention can be implemented
in an eyeglass frame type of aid as shown in FIG. 4. Referring to
FIG. 4, there is shown a temple 55 of an eyeglass frame, the temple
having a differential transducer and a network of sound conducting
passages mounted therein as shown more particularly in FIG. 5. The
temple further has a front aperture 56 and a rear aperture 58, each
of which is disposed on the downward facing surface of temple 55. A
manual valve 62 is disposed in the temple between the front and
rear apertures 56 and 58 and protrudes through the top of the
temple. The associated elements of the hearing aid, such as
processing electronic circuitry 66 and volume control 68, are
disposed in temple 55 in any convenient packaging arrangement. An
earpiece 70 is provided for mounting in the ear of the user and is
coupled to receiver 71 by means of a tube 72.
Referring now to FIG. 5 the internal arrangement of ports within
temple 55 will be described. Forward aperture 56 communicates via
channel 81 with first input port 82 of transducer 90. Passage 83
provides a sound path from channel 81 to valve 62. Passage 84
provides a sound path between valve 62 and a second input port 86
of transducer 90. Passage 85 provides a sound path between valve 62
and rear aperture 58.
The control valve 62 includes a cylinder 100 disposed within a
cylindrical recess formed transversely across temple 55 and in
which cylinder 100 is rotatable by action of a manual force applied
to control valve stem 64. An acoustic filter 92 having a
cylindrical hold 93 therethrough is disposed in passage 83 between
the valve 62 and the intersection of path 83 with channel 81.
An opening 102 is provided through cylinder 100 and in one
position, as depicted in FIG. 5, passage 85 is occluded by the
solid portion of cylinder 100 and a sound communication path is
provided to allow aperture 56 to communicate with the first sound
port 82 of transducer 90 through channel 81 and with the second
sound port 86 of transducer 90 through channel 81, filter 92,
passages 83 and 84. This represents the non-directional mode of
operation which is as previously described for the behind-the-ear
embodiment of the invention.
With valve 62 in the other position, sound entering rear aperture
58 comunicates through passages 85 and 84 with the second sound
port 86, and passage 83 is occluded. This represents the
directional mode of operation as previously described for the
behind-the-ear embodiment of the invention.
It will be appreciated that the invention can be implemented in
different ways to suit particular operation requirements. For
example, the control valve can be of many different configurations
to provide the intended function and the particular sound
communication paths between the front and rear apertures for
coupling forward and rearward sounds to the differential transducer
can be selected to suit specific constructional requirements of a
particular embodiment. Accordingly, it is not intended to limit the
invention by what has been particularly shown and described except
as indicated in the accompanying claims.
* * * * *