U.S. patent number 3,718,763 [Application Number 05/100,054] was granted by the patent office on 1973-02-27 for audiometer apparatus.
This patent grant is currently assigned to Beltone Electronics Corporation. Invention is credited to Vernon W. Cannon, Gordon N. Stowe.
United States Patent |
3,718,763 |
Cannon , et al. |
February 27, 1973 |
AUDIOMETER APPARATUS
Abstract
Disclosed is audiometer apparatus including a tone generator
portion, attenuator network, accoustical transducer and
two-dimensional plotting mechanism for automatically recording the
subject's response to signals received at the transducer. The tone
generator includes a plurality of continuous running oscillators
whose discrete frequency signals are coupled through pulser
circuitry to the attenuator by way of magnetic reed switches
actuated by the movement of the plotter. Hearing loss information
is plotted with a pair of different color ink pens disposed within
a carriage on the plotting mechanism. Switching mechanisms control
the movement of the plotter and the carriage in their respective
directions, selectively move the pens into and out of contact with
recording material, and switch the signals received by the
transducer from one earpiece to the other. Random validity
mechanism is incorporated with apparatus for periodically or
manually inserting an additional intensity change to the generated
tones. Pulser circuitry, utilizing a photoresistor, is adapted for
periodic interruption of the generated signal, the rise and decay
characteristics of the generated signal being controlled by the
circuitry.
Inventors: |
Cannon; Vernon W. (Austin,
TX), Stowe; Gordon N. (Northbrook, IL) |
Assignee: |
Beltone Electronics Corporation
(Chicago, IL)
|
Family
ID: |
22277890 |
Appl.
No.: |
05/100,054 |
Filed: |
December 21, 1970 |
Current U.S.
Class: |
73/585;
346/33ME |
Current CPC
Class: |
A61B
5/12 (20130101) |
Current International
Class: |
A61B
5/12 (20060101); H04r 029/00 () |
Field of
Search: |
;179/1N,1MN,1AA |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Blakeslee; Ralph D.
Assistant Examiner: Leaheey; Jon Bradford
Claims
What is claimed is:
1. In an audiometer of the type including tone generating means for
producing a plurality of discrete frequency signals, attenuator
means for varying the intensity of said frequency signals, an audio
output portion for receiving said varying intensity frequency
signals, and plotting means for recording information
representative of signals received by said audio output portion,
the improvement comprising:
a. a plurality of continuous running oscillators providing said
tone generator means, said oscillators producing output signals
having respectively separate and distinct frequencies,
b. switching means coupling said tone generator means to said audio
output portion, said switching means comprising a plurality of
first means respectively directly connected to said oscillators,
select ones of said plurality of first means, when actuated,
coupling the output signals from the respectively connected
oscillator to the attenuator means; said switching means also
comprising a plurality of second means, select ones of said second
means, when excited, actuating the said select ones of said first
means, and
c. means carried by said plotting means for actuating the select
ones of said second means.
2. The improvement as described in claim 1 wherein said plurality
of first means are normally open magnetic reed switches, said
plurality of second means are coils in proximity with said
plurality of first means, and the means carried by said plotter is
effective to selectively cause current to flow through said
coils.
3. The improvement as described in claim 2 including an insulating
substrate having formed thereon a plurality of electrically
isolated contact terminals respectively electrically connected to
one end of said plurality of coils and an elongated contact
terminal electrically connected to a voltage source of one
polarity; a second voltage source of relatively opposite polarity
electrically connected to the other end of said plurality of coils;
and switching means carried by said plotter for selectively
coupling said electrically isolated contact terminals with said
elongated contact terminal.
4. Audiometer apparatus, comprising:
a. a tone generator portion for producing signals of discrete and
differing frequencies,
b. intensity varying means for altering the intensity of said
signals,
c. acoustical transducer means including an earphone having right
and left ear engaging portions for reproducing said varying
intensity signals,
d. two-dimensional plotting means for recording information on
record material associated therewith representative of said varying
intensity signals reproduced by said acoustical transducer as a
function of the different frequencies thereof, said plotting means
carrying first switching means for selectively coupling select
frequency signals from said tone generator to said acoustical
transducer means as said plotting means moves in one dimension with
respect to said record material,
e. carriage means carried by said plotting means movable in the
other dimension with respect to said record material, said carriage
means coupled to said intensity varying means so that as said
carriage means moves in said other dimension, the intensity of the
signal reproduced by said acoustical transducer means is varied,
said carriage means also supporting a pair of writing implements
for marking said record material, the characteristics of the mark
produced by one of said writing implements when in contact with
said record material differing from the characteristics of the mark
produced by the other of said writing implements,
f. means for first selectively presenting the varying intensity
signals to one of the said ear engaging portions and moving only
one of said writing implements into contact with said record
material during said first selective presentation, and thereafter
secondly selectively presenting the varying intensity signals to
the other of said ear engaging portions and moving only the other
of said writing implements into contact with said record material
during the said second selective presentation,
g. means for selectively controlling the direction of travel of
said plotting means in said one dimension, and
h. means for selectively controlling the direction of travel of
said carriage means in said other dimension.
5. The apparatus as described in claim 4 wherein the said differing
characteristics of the marks produced by said writing implements is
color.
6. The apparatus as described in claim 4, wherein said tone
generator portion comprises a plurality of continuously running
oscillators, and furthermore including a bank of magnetically
actuated switches respectively coupled to the outputs of said
continuously running oscillators, the switching means carried by
said plotting means selectively actuating said magnetically
actuated switches.
7. The apparatus as described in claim 6 including an insulating
substrate member having a plurality of first conductive terminals
disposed thereupon respectively coupled to said magnetically
actuated switches, said plurality of first conductive terminals
arranged in a pair of vertically disposed rows with the conductive
terminals of one row coupled with the said magnetically actuated
switches coupled to the outputs of the oscillators producing
signals having frequencies adjacent the frequencies of the signals
produced by the oscillators coupled to the magnetically actuated
switches coupled to the conductive terminals of the other row,
portions of said conductive terminals of one row being vertically
aligned with portions of said conductive terminals of the other
row, a second plurality of conductive terminals disposed upon said
insulating substrate arranged in a row vertically disposed from
said first and second row, portions of said second plurality of
conductive terminals being vertically aligned with the vertically
aligned portions of the conductive terminals of said first and
second row, third conductive terminal disposed upon said insulating
substrate vertically disposed from the said first and second
plurality of conductive terminals, the said first switching means
carried by said plotting means selectively electrically connecting
the first, second, and third conductive terminals, thereby to
control the selective coupling of the frequency signals from the
said oscillators to said acoustical transducer means.
8. The audiometer apparatus as described in claim 4 including means
for randomly varying the intensity of said signals and moving one
of said writing implements out of contact with, and the other
writing implement in contact with, the said record material during
the time of said random variation.
9. The audiometer apparatus as described in claim 8 wherein said
first mentioned intensity varying means is an attenuator, and said
random varying means is a loss network comprising resistance means
which is periodically coupled with said attenuator to provide
additional attenuation of said signals.
10. The audiometer apparatus as described in claim 4 including
signal interrupting means coupled between said tone generator
portion and said acoustical transducer for controlled interruption
of the signals provided to said transducer.
11. The apparatus as described in claim 10 wherein said
interrupting means comprises input and output terminals; variable
impedance means coupled between said input and output terminals,
said variable impedance means including a variable impedance
photoresistor having two sections thereof; a source of light
directed to said photoresistor; first means coupled to said light
source for controlling the intensity of light impinging on said
photoresistor, thereby to control the impedance presented to and
the interruption of said signals at said input terminal; second
means for controlling the attenuation and the decay time of the
said signals at said input terminal, said means being coupled
between said first means and an intermediate point between said two
sections of said photoresistor, said second means including a first
transistor having its base coupled to said intermediate point and
its emitter shunting a portion of said variable impedance means; a
field effect transistor having its source and drain terminals
respectively coupled to the collector and base of said first
transistor, the gate electrode of said field effect transistor
being connected through a resistor-capacitor timing network to said
first means.
12. The apparatus as described in claim 7, including signal
interrupting means coupled between said tone generator portion and
said acoustical transducer for controlled interruption of the
signals provided to said transducer, and furthermore including a
fourth plurality of conductive terminals disposed upon said
insulating substrate in a row vertically disposed from said first,
second, and third plurality of conductive terminals, each of said
fourth plurality being aligned with the aligned portions of the
conductive terminals of said first and second row, said fourth
plurality being electrically coupled to said signal interrupting
means, said first switching means including means for coupling
select ones of said fourth plurality to said third conductive
terminal, thereby to interrupt signals from said tone generator
during the switching of one frequency signal to another frequency
signal to said transducer.
13. An audiometer comprising the combination of tone generating
means for producing a plurality of discrete frequency signals,
attenuator means connected to said tone generating means for
varying the intensity of said discrete frequency signals, audio
output means connected to said attenuator means for receiving the
varying intensity frequency signals, plotting means for recording
information representative of the signals received from said audio
output means, and means for randomly varying the intensity of said
frequency signals, said last-named means including additional
resistance means caused to be periodically coupled to the
attenuator means at intervals of time unknown to the audiometer
operator or to the subject being tested.
14. An audiometer as described in claim 13 wherein said means for
randomly varying the intensity of said discrete frequency signals
comprises magnetically operated switch means effective when closed
for coupling said additional resistance means to said attenuator
means, and magnetic means periodically operated for effecting the
periodic closing of said switch means.
15. An audiometer as described in claim 14 wherein said additional
resistance means is a loss network which, when coupled to said
attenuator means, increases the attenuation of said discrete
frequency signals.
Description
This invention relates generally to audiometers, more particularly
to improvements in automatic audiometers, and even more
particularly to improvements in the tone generation, tone
intensity, frequency selection, and plotter portions of
audiometers.
Audiometers have been used for many years as a basic tool for the
testing of hearing and, as such, have been employed by industry,
schools, the military, and others, to provide initial screening of
individual hearing sensitivity, as well as by the medical
profession to detect the presence of hearing defects and diseases
in humans.
Basically these audiometers comprise a tone generator portion for
furnishing audio signals of discrete frequencies to a set of
earphones worn by the subject being tested, an intensity varying or
attenuator portion for varying the intensity level of the generated
tone, and some type of means for recording the hearing sensitivity
of the individual being tested in response to the varying frequency
and intensity tones being presented thereto.
The increased use of and reliance upon the audiometer have also
demanded that equipment be developed which, among other things, is
substantially automatic or self-recording to reduce dependency upon
operator-technician accuracy; provide a permanent and accurate
record of the hearing status of both ears of the subject being
tested; and afford minimum maintenance and ease of servicing. In
addition, it has been found that it is important that some means be
incorporated into the audiometer which can detect the malinger or
one who is intentionally attempting to alter the true test results.
To meet these objectives, many forms and designs of audiometers
have been developed in the past, all of which have many
disadvantages associated therewith.
It is therefore a primary object of the invention to provide a new
and improved audiometer whose operation and construction overcomes
previous deficiencies and offers advantages heretofore
unobtainable.
It is a further object of the invention to provide improved
audiometer apparatus which is automatic or self recording, provides
a permanent, continuous, and accurate record of the hearing
sensitivity of the subject being tested, and offers increased
reliability in the test results obtained therefrom.
It is a still further object of the invention to provide a new and
unique means for the selective switching of the different frequency
audio signals to the earphones worn by the test subject.
It is an even still further object of the invention to provide a
new and improved non-mechanical signal interrupter or pulser, which
interrupter can be advantageously employed in an audiometer to
reduce the eardrum fatigue normally associated with a continuous
tone as well as to eliminate key clicks normally associated with
the switching from one frequency to the other.
Another object of the invention is to provide improvements in two
dimensional plotting apparatus, which improvements may be
advantageously incorporated into the plotting mechanism of an
audiometer for automatically recording the hearing status of the
subject being tested.
Another object of the invention is the provision of a random
validity test which is programmed into the operational sequences of
the audiometer to insure the accuracy and reliability of the test
results.
In accordance with these and other objects, the present invention
is directed to audiometer apparatus which not only embodies an
overall improved and unique construction and operation, but
incorporates subsystems which are novel and unique in themselves,
and offers particular adaptability to audiometer apparatus of the
type described.
Accordingly, the apparatus includes a tone generator portion which,
in its preferred embodiment, comprises a bank of continuously
running oscillators for respectively producing a plurality of
output signals of different frequencies, the output signals
therefrom being selectively switched by a unique switching system
through an attenuator network to an output audio portion coupled to
a set of earphones. Improved two-dimensional plotting apparatus is
provided for recording information, and in particular information
representative of the variable intensity and frequency signals
received by the earphones. The plotting apparatus includes carriage
means supporting a pair of writing implements for recording the
hearing sensitivity of the subject being tested, the movement of
the plotting apparatus, carriage means, and the writing implements
being uniquely controlled by mechanisms and circuitry subsequently
described. Means are also provided for the selective coupling of
the generated signals to either one or the other earpiece of the
set of earphones.
Signal interrupting apparatus of unique construction is
advantageously incorporated between the tone generator portion and
the intensity varying or attenuator portion for selective
interruption of the signals being received at the output audio
portion. Additionally, a random validity mechanism is incorporated
with the audiometer apparatus for periodically or manually
inserting an additional intensity change of the generated tones,
this insertion, in the preferred embodiment, being periodically
effected by magnetically operated switching means which couples
additional resistance with the attenuator network of the
apparatus.
Additional features of the invention, as well as further objects
and advantages thereof, will become apparent with reference to the
following detailed description taken in conjunction with the
drawings, in which:
FIG. 1 illustrates a perspective view of the external housing of
the audiometer of the present invention;
FIG. 2 is an overall block diagram schematic of the preferred
embodiment of the invention;
FIG. 3 is a partial sectional view of the audiometer taken along
the section line 3--3 of FIG. 1, illustrating the improved plotting
mechanism of the invention;
FIG. 4 is a partial sectional view of the plotting mechanism taken
along section line 4--4 of FIG. 3, illustrating additional details
of the plotting mechanism;
FIG. 5 is a plan view of a portion of the plotting mechanism
illustrating the pen carriage;
FIG. 6 is an exploded perspective view of the pen carriage assembly
of the plotting mechanism;
FIG. 6a is an enlarged plan view of the pen carriage;
FIG. 7 is a view, partially in section, showing the motor drive for
the overall plotting mechanism, taken along the line 7--7 of FIG.
3.
FIG. 8 is a schematic of the improved tone or signal interrupter of
the present invention;
FIG. 9 is a view, partially schematic, of the improved switching
mechanism of the audiometer of the present invention; and
FIG. 10 is an illustration of a typical record of the hearing
response of one ear produced by operation of the audiometer of the
present invention.
Referring now to the drawings, wherein like reference characters
designate like or corresponding parts throughout the several views,
there is shown in FIG. 1 an audiometer 20 for use in testing
hearing and an earphone assembly 22 with ear pieces 25a and 25b
electrically connected to the audiometer 20 through cable 24. The
audiometer 20 has a cover 26, a carrying handle 27 and a control
panel 28. The unit 20, due to its size and construction, is
lightweight and portable.
During the course of the test, the earphone assembly 22 is placed
over the ears of the test subject, tones of varying frequency and
intensity being alternately and automatically presented to the
right and left ears through ear pieces 25a and 25b, as subsequently
described. A two-dimensional plotter 30 for permanently recording
the subjects response to these tones is disposed over a sheet
record material 32 mounted thereunder, holes 31 provided therein to
enable the record material 32 to be properly indexed with the
plotter 30.
Referring now to FIG. 2, the audiometer 20 includes a tone
generator portion 200 comprising a bank of oscillators 201a through
201f for respectively producing discrete frequency signals or tones
as, for example, 500 Hz, 1,000 Hz, 2,000 Hz, 3,000 Hz, 4,000 Hz,
and 6,000 Hz. While each of these oscillators may be of a
conventional design, as a significant feature herein, each
oscillator is a continuous running unit having a substantially
constant output amplitude.
A unique switching network 202 couples the output signals from a
selected one of the oscillators to the input of a tone interrupter
or signal pulser 205 and thereafter to the audio output portion of
the system. More specifically, the network 202 includes a plurality
of magnetic reed switches 203a through 203f. Individual coils 204a
through 204f are respectively associated with each reed, the coils
204 being connected between a common positive voltage supply and
respective contact terminals 190-196. When a selected coil 204 is
excited, it is effective to close its associated reed switch 203 in
a manner well known in the art, the so-closed reed thus coupling
the output signal from its associated oscillator 201 to the input
of pulser 205.
Selective excitation of the coils 204a through 204f is accomplished
by the connection of the terminals 190-196, respectively, to a
common negative voltage bus bar 186 by way of a sliding contact
assembly 170 carried by the plotter 30. As a consequence, the
individual frequency signals or tones are sequentially applied to
the input of the pulser 205 as the plotter 30 proceeds along its
path of travel in the horizontal or X direction. For example, in
the system illustrated in FIG. 2, as the plotter proceeds from left
to right, sequentially coupling the terminals 190-196 to the bus
bar 186, an initial 1,000 Hz practice tone is selectively switched
from the output of oscillator 201b to the pulser input, followed
sequentially by 500 Hz, 1,000 Hz, 2,000 Hz, 3,000 Hz, 4,000 Hz, and
6,000 Hz tones. It is thus observed that the output signals from
each of the continuously running units may be switched to the audio
output portion of the network by use of a non-mechanical indirect
switching technique whereby the switch portions 203a- 203f
themselves are protected against fusion, environmental corrosion,
and other deleterious effects which could adversely affect the
switching operation.
The selected output signals or tones from the network 200 are thus
applied to a tone interrupter or pulser 205. When the network 205
is in the CONSTANT position or mode, the tone signals inputed
thereto pass through and are uninterrupted or substantially
unaffected. When the pulser 205 is in the AUTO position, however,
the network 205 is effective to periodically interrupt the tone. As
subsequently described, temporary disconnection of the output
signals from the tone generator portion 200 may also be effected
utilizing the network 205 during the switching from one frequency
to another, thereby eliminating the key clicks normally associated
with this switching. Control of the rise and decay of the frequency
signals or tones during the pulsing and disconnect operation is
also maintained by circuitry 205, as subsequently described in
greater detail.
The pulsed or constant tone, whichever the case may be, is
thereafter coupled from the output of the interrupter 205 through a
conventional amplifier 206 to an attenuator network 207 for varying
the intensity of the tone being applied thereto. The attenuator is
of conventional design known in the art and may be a
ladder-resistor arrangement, as illustrated. A sliding contact 208
mechanically coupled to the carriage 54 of the plotter 30 varies
the location of the application of the output signal from amplifier
206 to this attenuator network in response to the Y-axis movement
of the carriage 54, thus varying the intensity or attenuation of
the tone at the output of the network 207. The attenuated frequency
signal is thereafter coupled through relays 209 and 210 to either
the right or left earpiece 25a or 25b, respectively, as
subsequently more fully described.
The plotting of the hearing sensitivity is effected by the X-Y
plotter 30 in combination with a sheet of record material 32 which
is suitably positioned under the plotter 30. The plotter 30 is
moved in the forward direction in the X plane by low-speed motor 42
mechanically coupled thereto, and is moved in the rearward
direction in the X plane by high speed motor 43, each motor being
selectively engaged as required. The plotter 30 carries a pen
carriage member 54 which is reversibly movable in the vertical or Y
plane by a motor 86. The carriage 54 carries two marking pens 79
and 81, each of which can be selectively engaged with the record
material 32. These pens are desirably of different colors or other
distinguishing characteristics (such as different point widths) so
that a record of the response of both ears of a test subject can be
recorded and distinguished on a single sheet of record material 32.
This can be accomplished by having the pen 79 in engagement with
the record material 32 during the testing of the right ear, for
example, while the pen 81 is in engagement with the record material
during the testing of the left ear.
During the testing operation, the plotter 30 is initially disposed
in the left-most position with one of the pens, for example pen 79,
in contact with the record material 32 and the signal being
presented to one of the ear pieces, for example 25a. The plotter 30
is then moved to the right at a continuous rate by X motor 42
during which time switch mechanism 170 selectively presents various
frequencies of audio sound to the earphone 25a. During this period,
the carriage 54 (and the sliding contact assembly 208) is
alternately traveling in opposite directions in the vertical or Y
plane, this vertical movement being controlled by reversible motor
86. As a consequence, a trace of hearing sensitivity is made on the
record 32 in response to the frequency and intensity changes of the
tone being presented to the subject.
When the plotter 30 reaches the right-most position, the motor 42
is disengaged, the motor 43 engaged, the pen 79 is lifted from the
paper, and the plotter 30 is moved to the left-most position. When
the plotter 30 reaches this left-most position, the pen 81 is
placed in engagement with the paper, the motor 43 is disengaged,
and the motor 42 is again engaged to drive the plotter 30 in the
forward X direction. The various frequencies and intensities are
again presented this time to the other ear through earphone 25b
until the plotter 30 reaches the right-most position whereupon the
motor 42 is again disengaged, and motor 43 is engaged to return the
carriage to the left-most position, the test thereby being
completed.
The motors 42 and 43, which are normally running when power is
applied thereto, have electrically actuated means for the
respective engagement and disengagement of clutches (59, 61) of
these motors (and the consequent relative movement of the plotter
30 in the X plane), the engagement and disengagement of the
respective motor clutches (thus the engagement and disengagement of
the motors) are controlled by relay 215 electrically connected
thereto; the relay 215 when actuated, causes the plotter 30 to be
driven in either the forward or reverse direction. Actuation of
this relay 215 is, in turn, effected by a number of inputs thereto.
Specifically, forward travel of the plotter 30 is initially
effected by depression of start switch 218 which, through
cooperation of logic amplifier 218a, actuates relay 219, the relay
219 then actuating relay 215 to engage motor 42 and disengage motor
43. When plotter 30 reaches the right-most position (the testing of
one ear having thus been completed, as subsequently described), it
engages limit switch 217 which then actuates relay 215 to disengage
forward motor 42 and engage return motor 43, the plotter 30 thus
being returned to its starting position. When plotter 30 reaches
this left-most position, limit switch 216 is engaged to actuate
relay 215 to disengage motor 43 and engage motor 42 to again move
plotter 30 in the forward direction (during which time the testing
of the other ear is effected) until limit switch 217 is again
reached and plotter 30 returned as before. End cycle lockout switch
223 which is connected through relay 210 to the power source (not
shown) for motors 42 and 43, is effective to assure that the motors
42 and 43 remain energized during the test cycle of both ears, and
de-energizes the motors 42 and 43 when the plotter 30 reaches the
left-most position after the second ear has been tested.
External stop-switch 220, when depressed, actuates relay 215
through cooperation with logic amplifier 221 to disengage motor 42
and engage motor 43 to return plotter 30 to the left-most position
and engage switch 223. Limit switch 222 assures that initiation of
movement of plotter 30 in the forward direction occurs only after
plotter 30 has first reached the left-most position. As another
particular feature herein, a number of audiometers 20 may be
coupled together for simultaneous testing of many subjects.
Initiation of the testing cycles for all of these apparatus may
then be effected by a signal received from external start means
218b, rather than from depression of switch 218.
During the motion of the plotter 30 in the forward X direction, the
Y position of the carriage 54 on the plotter (consequently the
intensity of the sound presented to the particular earphone as well
as the position of the marking pen along record 32) is controlled
by the reversible Y motor 86 which, in turn, is controlled by relay
212 which, when actuated, is effective to alternately change the
direction of rotation of the motor 86. A switch 211 is depressed or
released by the test subject in response to the apparent presence
or absence of sound detected by his ear, thereby actuating the
relay 212 to alternately move the carriage 54 back and forth, thus
making a record of the hearing sensitivity during the movement of
the plotter 30 in the forward X direction. Another input from relay
215 actuates the relay 212 to return the carriage 54 to the 0 db
position in response to the rearward or return movement of the
plotter 30.
Disengagement of motor 86 is effected by way of inputs coupled from
a minimum, say 0 db, limit switch 213 and a maximum, say 100 db,
limit switch 214 so that if the carriage 54 reaches the 0 or 100 db
level, switch 213 or 214, respectively, is effective to terminate
the direction of travel of the motor 86 and carriage 54.
Relay 210 is effective, when actuated, to switch the transmitted
audio signals or tones of varying frequency and intensity to either
the earpiece 25a or 25b. Initial actuation of this relay 210 is in
response to a pulse applied from logic amplifier 214 in response to
depression of start switch 218 (or signal from 218b). The relay 210
is also actuated to switch the audio signal from one earpiece to
the other when plotter 30 reaches the forward-most position to
engage limit switch 227'.
Relay 209 is effective to energize either pen marker solenoids 114
or 116 to selectively engage pen 79 or 81 with record material 32,
as well as to provide additional attenuation to the transmitted
tone, in accordance with a specific feature herein. Accordingly,
one input to relay 209 is provided from the output of relay 210 so
that whenever the tones are switches to earpieces 25a or 25b, the
respective pen solenoid 114 or 116 is actuated. A limit switch 226
is also engagable by the plotter 30 when it is disposed at its
forward-most position to deactuate both solenoids 114 and 116 to
lift both pens 79 and 81 and prevent their contact with record
material 32 during return of the plotter 30 to its left-most
position.
As a particular feature of the invention, an additional loss
network is provided within relay network 209, the loss network,
when inserted, providing additional attenuation (decreased
intensity) of the audio signal being presented to the test subject.
In this respect, magnetic reed switch 229, when closed, inserts
this network as, for example, by incorporating additional
resistance with attenuator 207. Closing of the switch 229 is
effected by a magnet 251 which is periodically rotated in
communication with the magnetically actuated reed switch 229 by
motor 250. In this manner, when the motor 250 is started, a random
insertion of additional attenuation to the tone is provided at a
time unknown to the subject being tested. Insertion of the extra
attenuating network may also be manually effected by depression of
switch 228.
Referring now to FIG. 3, a detail of the plotter 30 is shown with
the cover removed. The plotter 30 is constructed from a support
member 34, which is mounted to move along elongated tracks 36.
These tracks 36 (FIGS. 3 and 5) are attached to the audiometer, and
are positioned with their lengths parallel to the X direction of
the plotter travel shown by the arrow in FIG. 1. A plurality of
rollers 38 are mounted to rotate about shafts 40 and are positioned
in cut-out portions 39 in the vertical members 44. These rollers 38
contact the upper surface of the elongated track 36 to roll
therealong. By mounting the support 34 in this manner, it is free
to move along the tracks 36 in an X direction while being supported
by rollers 38.
A suitable motor assembly 40a (comprising motors 42 and 43) can be
provided to move the support 34 along the track 36 in the X
direction. This assembly is shown in detail in FIG. 7 as having a
support 41 attached to a horizontal member 46 with the forward X
motor 42 and the high speed return X motor 43 mounted thereon.
These two X motors have extending lower flanges 45 which are
pivotably mounted on the support 41 by pins 47 so that the motors
can rotate as shown by arrows 49. Each of the X motors is provided
with an upper flange 51 between which a tension coil spring 53 is
attached to resiliently urge the motors to rotate in a direction
toward each other. The motors each have a gear member 55 which
engages an elongated rack 57 which is in turn mounted on the frame
of the audiometer and extends along its length in the X direction.
It can be seen that by mounting the motors 42 and 43 in the above
described manner, that the spring 53 resiliently holds each motor
in engagement with the rack 57. The motors 42 and 43 are provided
with the electrically actuated clutches 59 and 61, respectively,
which can be actuated as previously described to selectively drive
the plotter 30 in the desired direction by either motor 42 or
43.
The carriage member 54 is mounted for reciprocating movement in the
Y direction along the guide members 48 as shown by the arrows in
FIGS. 2, 3, and 5. The carriage is provided with a plurality of
rollers 63 which contact and support the carriage on the upper
surface of the guide members 48.
By examining FIG. 6, the details of the construction of the
carriage member 54 can be seen as consisting of two identical
plate-like side members 56 arranged in a spaced parallel
relationship and having V shaped grooves 58 on the inside faces.
These inside faces of the plate members 56 are also provided with
two parallel spaced grooves or cut-out portions 60. These two side
members 56 are held together at their ends by end pieces 62 and 64
to form a rigid rectangular-shaped carriage.
Two slide members 66 and 68 are each provided with two extending
flanges 70 on their outer faces. These two flanges 70 are of a size
and relative spacing so that they mate with and slide in the
grooves 60. The two slide members 66 and 68 are also each provided
with two vertically extending openings or slots 72 and 74 which are
centered in the vertical grooves 75 and 76, respectively. A first
and second U-shaped pen holder 78 and 80 respectively, are provided
to support the marking pens 79 and 81 in mounting openings 83. The
pens 79 and 81 have different color ink and are desirably of the
capillary feed type known in the art. The pen holder 78 has two
pins 82 which are inserted through the openings 72 in the slide
members 66 and 68 and then into the V-shaped grooves 58.
Correspondingly, the pen holder 80 is provided with its two pins 84
which are inserted through the respective openings 74 in the slide
members 66 and 68 and thereafter into the V-shaped grooves 58. The
relative dimensions of the pins 82 and 84 and the grooves 58 are
such that the pen holders 78 and 80 are free to move in the
vertical direction when the pins 82 and 84 are engaged in and
movable with respect to the groove 58. The pen holders 78 and 80
during the vertical movement are adapted to slide in grooves 75 and
76, respectively.
Y motor 86 (shown in FIGS. 3, 4 and 6) is attached to and carried
by the plotter 30. This Y motor is a reversible AC type and has a
drive wheel 100 attached to an output shaft 102. The drive shaft
102 passes completely through the wheel 100 and into an attenuator
housing 104 in which the attenuator portion 207 is disposed, the
housing 104 being suitably mounted on the plotter 30. As can be
seen in FIG. 6, a positioning cord 106 has one end attached to end
piece 62 at 108 with the other end attached to other end piece 64
at 110. The cord 106 engages a plurality of positioning pulleys 112
and is wrapped around the drive wheel 100. Means are provided (not
shown) for preventing slippage of the cord 106 on the drive wheel
100, so that as the drive wheel 100 is rotated in the clockwise
direction, tension is placed on the positioning cord 106 on the
right hand side, and the carriage member 54 is pulled along the
guide rods 48 in the direction of arrow 113. It can also be seen
that when the drive wheel 100 is rotated in a counterclockwise
direction, the positioning cord 106 is tensioned on the left hand
side, and the carriage member 54 is moved along the guide rods 48
in the direction of arrow 115. It can thus be seen that the
position of the carriage 54 can be selected by operation of the
motor 86.
Turning now to the pen switching mechanism, two solenoids 114 and
116 are provided with translatable shafts 118 and 120 extending
respectively therefrom. Actuation of the two solenoids 114 and 116
will result in the retraction of the shafts 118 and 120,
respectively. The shafts 118 and 120 are pivotally attached to
right and left leg members 122 and 124 at pivot points 126. These
two leg members 122 and 124 are pivotally attached at 128 to a
support 130. The support 130 is fixed to the horizontal member 46
and at right angles thereto (FIG. 4). The two leg members 122 and
124 are connected by a spanning member 132 so that when one of the
leg members is moved, the movement is transmitted through the
spanning member 132 to the other leg member. A right spanning
pulley 134 and a left spanning pulley 136 are rotatably mounted on
the spanning member 132 and are spaced apart as shown in FIG. 6. It
can thus be seen that the leg members can be moved in either
direction about their pivots 128 by the actuation of the solenoids
114 and 116 so that actuation of solenoid 114 rotates the right leg
122 and left leg 124 in a counterclockwise direction about its
pivot points 128, thus moving the spanning member 132 from left to
right. By actuation of the solenoid 116, the whole assembly is
moved in the opposite direction.
A first pin actuation cord 138 has one end attached to side members
66 and 68 by means of a rod 140 and passes through an opening 142
in the end piece 62 and from there around pulleys 144 and 145. The
cord 138 then passes around an idler pulley 146, around the left
hand spanning pulley 136, by another idler pulley 147, down the
length of the support 46, and around pulleys 148 and 149, and is
thereafter attached to the end piece 64 at 150.
A second pin actuation cord 152 is attached to the side members 66
and 68 by a rod 153. The cord 152 then passes through an opening
154 in the end piece 64, around pulleys 155 and 156, then around
idler pulley 158 and right hand spanning pulley 134, thereafter
around another idler pulley 160 and pulleys 161 and 162, and is
thereafter attached to the end piece 62 at 163.
Right and left hand spring members 165 and 166, respectively, are
attached between the support member 130 and the right and left hand
leg members 122 and 124, respectively. These springs maintain the
leg members 122 and 124 in a central position when neither of the
solenoids 114 and 116 are actuated.
Operation of the pen switching portion of the plotter 30 is as
follows. If it is desired to move marking pen 79 into contact with
the record material 32, solenoid 114 is actuated to move the
spanning member 132 to the right, thus tensioning pin actuation
cord 152 and moving slide members 66 and 68 in the direction of
arrow 113. This relative movement causes the pins 82 and 84 to also
move in the direction of arrow 113 along grooves 58 in side members
56 with the pins 82 thus moving down toward the apex 117 of the
grooves 58, the pins 84 moving toward upper right hand portion 119
of the grooves 58. This movement lowers pen holder 78 downward
until the pen 79 contacts the record material 32 while the pin 81
and holder 80 are correspondingly moved away from the record
material 32.
Conversely, to move marking pin 81 into contact with the record
material, solenoid 116 is actuated, thus tensioning pin actuation
cord 138 and moving slide members 66 and 68 in the direction of
arrow 115, pen holder 78 moving toward upper left hand portion 121,
and pen holder 80 moving downward toward apex 117, pen 81 thereby
being moved into contact with the record material 32 in the same
manner as described with respect to pin 79 above.
It should also be noted that the pen switching mechanism is so
designed that when it is desired to switch from a first pen to a
second pen, the second pen will be moved to begin its marking at
the same spot that the first pen discontinued its marking. This is
accomplished by means of the above-described unique structure of
the pen switching mechanism and by examining FIG. 6a, the
advantages of this structure can be more fully appreciated.
Initially, it is important to appreciate that pens 79 and 81 are
centrally positioned in the pen holders 78 and 80, respectively.
These pen holders 78 and 80 and the slide members 66 and 68 are
constructed so distance (A) measured between one end of the slide
members and the pen 81 and distance (B) measured between the other
end of the slide members and pen 79 remain constant during the pen
switching operation. By selecting dimension (C) measured between
the inside surfaces of the end pieces 62 and 64 to equal distance
(A) plus distance (B), each pen is moved to begin marking at the
same spot enabling the pens to be switched during the test without
affecting the accuracy of the record. It can also be seen that the
pens are mounted in such a manner that they are held against the
record material solely by the gravitational force of the weight of
each pen and its respective holder.
Referring now to FIG. 8, there is illustrated the unique pulser or
interrupter circuitry 205. Accordingly, the selected signal or tone
from switching network 202 is applied at input terminals A and A'
to a resistor bridging network 300 comprising fixed resistors
R.sub.14, R.sub.15 and R.sub.16, and variable resistor means 301.
In accordance with a specific feature of the invention, the
variable impedance element 301 is a photoresistor having two
sections 301a and 301b, the resistance of which is controlled by
the incidence of light received from a lamp 303 adjacent thereto.
The photoresistor 301 and lamp 303 are normally packaged together
in a light tight enclosure so that stray light does not affect the
operation of the unit. Maximum impedance of the photoresistor 301
(and therefore maximum attenuation of the incoming signal) occurs
when the light output from the lamp 303 is at its minimum, and
conversely minimum attenuation of the incoming signal is achieved
when the light output is at its maximum. Thus, interruption of the
incoming signal from 202 may be controlled by regulating the
current input to lamp 303.
This regulation is effected by a conventional free-running
multivibrator or flip-flop network 305 comprising matched
cross-coupled transistors Q.sub.3 and Q.sub.4, emitter bias and
feedback resistors R.sub.7 and R.sub.10, and collector load
resistors R.sub.9 and R.sub.12. Frequency of oscillation of the
multivibrator is determined by resistor-capacitor pairs (R.sub.8
and C.sub.4) and (R.sub.11 and C.sub.5), all as presently known in
the art. Desirably, the conduction times of transistors Q.sub.3 and
Q.sub.4 are equal, thus providing substantially equal pulsing of
the incoming signal from 202. Zener regulation of the collector
voltage and filtering is accomplished in conventional manner by
zener diode Z.sub.1, bypass capacitor C.sub.6, and resistor
R.sub.13.
The lamp 303 is connected in the collector leg of one of the
transistors, for example Q.sub.3, and is excited in response to
actuation of, and current flow through, transistor Q.sub.3. An
external switch control 310 coupled to the base of transistor
Q.sub.4 determines the state of conduction of transistor Q.sub.3 as
follows. When switch 310 is switched to the AUTO position, (thus
opening the connection to the base of transistor Q.sub.4) the
multivibrator will oscillate at its operating frequency, the
alternating conduction and nonconduction of the transistor Q.sub.3
thereby causing the lamp 303 to glow or darken, thereby producing a
pulsed output signal at terminals B-B'. When the switch 310 is
moved to the CONSTANT position, the positive voltage applied
through the external resistor 309 is applied to the base of
Q.sub.4, the transistor Q.sub.3 thereby being locked into the
conduction mode, and the incoming signal from 202 passes through
the network 205 with a minimum of attenuation. Conversely, when the
switch 310 is moved to the OFF position, a negative voltage from
bus bar 186 maintains the transistor Q.sub.3 in nonconduction
(Q.sub.4 being in conduction), the output from lamp 303 at a
minimum and the consequent high value of resistance presented by
resistor 301 providing maximum attenuation of the incoming
signal.
The rise and decay characteristics of the interrupted tone signal
from means 202 are controlled in the following manner. The attack
(or rise) time is controlled by the current supplied to the lamp
303, the lower the current, the longer the rise time.
As a significant feature of the circuitry, however, the decay time,
as well as the maximum attenuation of the incoming signal, is
controlled by the portion of the circuitry now described.
Transistor Q.sub.1, along with base bias resistors R.sub.1 and
R.sub.2, collector and emitter resistors R.sub.3 and R.sub.4,
respectively, provide a single stage Class A, common emitter
amplifier with emitter degeneration due to R.sub.4. Field effect
transistor Q.sub.2 has its source and drain terminals coupled to
the collector and base of transistor Q.sub.1, capacitor C.sub.2
providing DC blocking between drain of Q.sub.2 and base of Q.sub.1.
The base of transistor Q.sub.1 is connected through DC blocking
capacitor C.sub.1 intermediate the two sections of photoresistor
301.
When transistor Q.sub.2 is driven to saturation (turned "on"),
maximum shunt negative feedback is provided for Q.sub.1, the input
impedance Z.sub.in of transistor Q.sub.1 thereby being maintained
at a minimum. This low input impedance Z.sub.in shunts resistor
R.sub.15, increasing the overall resistance of network 300, and
increasing the attenuation of the incoming tone signal.
Triggering of the FET Q.sub.2 is effected by the coupling of the
gate electrode thereof to the collector leg of the transistor
Q.sub.4 through the decay timing network of resistors R.sub.5 and
R.sub.6 and capacitor C.sub.3. At the start time of maximum signal
attenuation (Q.sub.4 conducting) capacitor C.sub.3 is controlled
rate charged through resistor R.sub.6 and transistor Q.sub.4.
Conversely during the time of minimum signal attenuation (Q.sub.3
conducting), capacitor C.sub.3 discharges through resistors
R.sub.5, R.sub.6 and R.sub.12. In this manner, a controlled decay
time is maintained.
As previously described with reference to FIG. 2, the switching
mechanism 170 is mechanically coupled to plotter 30 so that as the
plotter moves in the X direction, discrete frequency tones are
sequentially presented to the test subject's ear. As observed in
FIGS. 3-5, and particularly FIG. 3, the switch mechanism 170
comprises a plurality of switch arms 172, 174, 176, 178 and 180
attached to the vertical member 44 and resiliently held against
switch plate 182.
This switching mechanism 170, as well as the switch plate 182,
which is attached to the body of the audiometer, is shown in
greater detail in FIG. 9. Accordingly, the switch plate 182 has a
rectangular shaped face or substrate 184 formed of electrically
nonconductive material upon which the contact terminals or pads are
disposed. A plurality of mounting slots 185 through which suitable
fasteners (not shown) can be inserted are provided for attachment
of the plate 182 to the audiometer.
Disposed along the line 180a are a plurality of conductive
terminals 198a, 198b, and 198c which are electrically connected by
means (not shown) to a positive voltage supply. Disposed along
lines 178a and 176a are conductive terminals 190-196 electrically
connected by means (not shown) to coils 204a-204f, as illustrated
in FIG. 2. Disposed along line 172a is bus line contact 186 coupled
to negative voltage source (-v).
In addition to the switching arms 172, 174, 176, 178 and 180,
mechanism 170 includes a relay 197 carried thereon which
operatively connects the switching arm 172 (and consequently bus
bar 186) to either switching arm 178 (and consequently pads 191,
193 or 195) or switching arm 176 (and consequently pads 190, 192,
194 or 196).
The terminal pads 190-196 are so spaced with respect to one another
that adjacent frequency pads (500 Hz and 1,000 Hz, 1,000 Hz and
2,000 Hz, etc.) slightly overlap one another, as illustrated. The
edges of the contact pads 198a, 198b, 198c are then disposed to be
in alignment with the areas of the overlapping portions. Thus, for
example as the switch mechanism 170 moves to the right in
conjunction with the plotter movement, the relay 197 is actuated
from B to the A position when the switch arm 180 reaches the
left-most edge of the contact 198b, for example, the frequency of
the tone to the test subject thus changing from 1,000 Hz to 2,000
Hz. Switching of the relay 197 back to the B position then occurs
when the switch arm 180 passes beyond the right end of contact pad
198b, the frequency then becoming 3,000 Hz. The overlapping of
frequency pads 190 and 191, 192 and 193, etc. thus avoids
discontinuities in these tones. While the switching arms 172, 174,
176, 178, and 180 are illustrated as being mutually aligned, use of
relay 197 avoids the necessity of direct alignment between arms 176
and 178, and enables the overlapping of the adjacent frequency pads
(190 and 191, 192 and 193, etc.).
As an additional feature, discrete contact pads 188 are provided
along a line 174a and have a portion of their areas in mutual
alignment with the overlapping areas of adjacent frequency pads 191
and 192, for example. Each of the pads 188 is electrically
connected by means (not shown) to the base of transistor Q.sub.4 of
pulser 205 illustrated in FIG. 8. Electrical connection of these
pads by switch arm 174 to negative bus line 186 thus corresponds to
to the OFF position of the switch 310 illustrated in FIG. 8. In
this manner, the tone may be temporarily interrupted during the
transition from one frequency to the next to eliminate the "clicks"
normally associated with this transition.
To conduct a test with the audiometer, earphone set 22 is placed
over the ears of the test subject and the plotter 30 is moved to
the left-most position. The audiometer is then turned on and a
1,000 cycle per second practice audio signal is presented to only
the right earpiece, for example, of the earphone set 22. During
this initial period, the X motors 42 and 43 remain disengaged so
that the plotter remains in the left-most position, but the Y motor
86 is in the "on" condition, its direction of rotation being
controlled by the hand switch 211, the test subject thus becoming
accustomed to the operation of the equipment.
Once a sufficient period of time has passed for the test subject to
become accustomed to the operation of the audiometer, the X motor
42 is engaged and the plotter is moved slowly to the right with pen
79 engaging the record material 32. As the plotter moves from left
to right, the switching mechanism 170 selectively presents the
initial 1,000 cycle test signal to the ear of the test subject and
thereafter the 500, 1,000, 2,000, 3,000, 4,000 and 6,000 cycles per
second audio signals. The record material 32 is aligned under the
plotter such that the transition between the presentation of audio
signals of different frequencies correspond to vertical lines 230,
231, 232, 233 and 234 on the record material 32, as shown in FIG.
10.
As previously described, the vertical position of the carriage 54
is controlled by the hand switch 211 which also, in turn, controls
the intensity of the sound presented to the ear of the test
subject. During the course of the test, the test subject regulates
the switch 211 to control the intensity of the sound presented to
his ear at his threshold of hearing. Since the carriage 54 carries
the marking pen 79, a record 235 of the vertical position of the
carriage 54 is made on the record material 32, an example of which
is shown in FIG. 10.
When the carriage 30 has completely moved across the record
material to the end of the last test frequency, pen 79 is lifted
from the record material 32 and the audio signal is removed from
the right earpiece. Also, when the plotter 30 reaches the
right-most position, the motor 42 is disengaged and motor 43 is
engaged to return the carriage to the left-most position whereupon
the pen 81 is moved into contact with the record material 32 and
the audio signal is presented to the left earphone whereupon the
plotter 30 moves to the right while the switch mechanism 170 causes
the above mentioned frequencies to again be selectively presented
to the left earphone. When the plotter 30 again reaches the
right-most position, the motor 42 is disengaged and motor 43 is
engaged to return the carriage to the left-most position, whereupon
the test is complete. By use of different color ink in pens 79 and
81, both the right and left ear hearing sensitivity may be recorded
on the same chart. FIG. 10 illustrates a typical record of a test
of one ear by the audiometer. Within each frequency increment a
large number of peaks and valleys are formed representing the
points at which the apparent sound disappeared and reoccurred. The
average of these recorded points thus represents the threshold of
hearing for the test subject at the given frequencies.
The audiometer also has provisions for a random or manual validity
test, as previously described, which may be applied during the
course of the hearing test either automatically by the audiometer
itself or by the test operator. In this portion of the test, the
tone was attenuated an additional 10 db, for example, the pens
being switched on the carriage 54 so that the different colored
record portion 236 indicated that the validity test was in
progress. By noting where the pens have changed, (by color change,
for example) the operator can determine when the validity test was
in progress, and at what frequency this occurred, and by noting the
subject's response to this change in intensity, to verify the
authenticity of the test. The validity mechanism itself is arranged
to randomly present the 10 db signal during the test so that
neither the operator nor the test subject will know when the
validity test will occur. The validity mechanism also enables the
operator to manually insert the 10 db attenuation, for example, to
the audio signal when he senses that the test subject is attempting
to alter the results of the test.
Variations to the disclosed embodiments may be made consistent with
the teachings of the present invention. For example, rather than
using different colored ink in the marking pens 79 and 80, other
means may be utilized to differentiate therebetween, for example
the line widths may be different.
Additionally, the validity test has been described by reference to
the insertion of additional attenuation to the audio signal
presented to the test subject. Alternatively, it may be desirable
to increase, rather than decrease, the intensity of the audio
signal during the validity test. Furthermore, it may be desirable,
particularly when testing individuals with high frequency hearing
loss, to begin the testing of each ear with the intensity level of
the tone at a minimum.
Various other alterations or modifications of the disclosed
embodiments, as well as other embodiments, may become apparent to
one skilled in the art without departing from the spirit and scope
of the invention as defined by the appended claims.
* * * * *