Handheld low voltage testing device

Handheld low voltage testing device
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US 20040059250A1
(19) United States
(12) Patent Application Publication (10) Pub. No.: US 2004/0059250 A1
Causcvic ct al.
(54)
(43) Pub. Date:
HANDHELD LOW VOLTAGE TESTING
Mar. 25, 2004
Publication Classi?cation
DEVICE
(76)
(51)
Int. Cl.7 .
Inventors: Elvir Causevic, Ellisville, MO (US);
(52)
US. Cl. ............................................................ .. 600/559
Eldar Causevic, Ellisville, MO (US);
Randall J. Krohn, WildWood, MO
(57)
(Us)
.... .. A61B 5/00
ABSTRACT
A portable hand-held electrical testing device including a
Correspondence Address;
POLSTER, LIEDER, WOODRUFF &
processor housed Within an enclosure. The processor is
con?gured to operate on commands by a user to process
LUCCHESI
sub-microvolt electrical signals received through an input/
12412 POWERSCOURT DRIVE SUITE 200
output interface. The input/output interface includes a
ST_ LOUIS, MO 631313615 (Us)
capacitive coupled ampli?er With adjustable gain settings.
Onboard memory linked to the processor stores processing
(21) Appl, N()_j
10/252,345
data and instructions. A display device is mounted to said
(22) Filed:
Sep. 23, 2002
display processing results in real time.
enclosure and is operatively connected to the processor to
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[email protected]
Mar. 25, 2004
US 2004/0059250 A1
HANDHELD LOW VOLTAGE TESTING DEVICE
non-economic costs such as parental anxiety incurred When
provided With incorrect information.
CROSS-REFERENCE TO RELATED
APPLICATIONS
[0007]
These costs, both actual and human, can be reduced
by reducing the cost per test, reducing the false positive rate,
and resolving false positive screening results at the bedside
prior to hospital discharge. The cost per screening can be
[0001] None.
reduced With a dedicated device optimiZed for screening in
any location and enhanced to alloW effective operation by
STATEMENT REGARDING FEDERALLY
SPONSORED RESEARCH
minimally trained personnel. The performance characteristic
[0002] Not Applicable.
of the device of our invention includes reduced measure
ment time, the ability to operate and con?gure Without an
BACKGROUND OF THE INVENTION
external computer, the ability to integrate and interpret all
[0003] This invention relates to the ?eld of loW voltage
electrical signal measurement devices and in particular, to
the design of a hand-held sub-microvolt electrical signal
test results, the ability to store large number of test results,
long battery life, and bi-directional Wireless transfer of data
to and from external devices.
measurement device. While the invention is described With
[0008]
particular emphasis to its use With auditory screening appli
First, the initial screening test performance can be improved
cations, those skilled in the art Will recogniZe the Wider
applicability of the inventive principles such as vibration
With enhanced signal processing, more ef?cient test param
monitoring, gas monitoring, blood analysis, and alcohol
false positive rates also can be reduced by providing a
mechanism for resolving an initial screening test failure at
the bedside at the time of the initial screening. This capa
intoximeters, such as disclosed hereinafter.
[0004] Test equipment capable of accurately measuring
loW voltage electrical signals in the sub-microvolt range has
a Wide range of applications from the monitoring of bio
electric signals in a human body, such as those found in the
auditory system, to vibration monitoring and the measure
ment of electrical signals from chemical reactions such as
found in alcohol intoximeters, more commonly referred to
as breathalyZers. LoW voltage electrical signals in the sub
microvolt range can be extremely dif?cult to detect, as often
the signal noise levels and interference present can mask the
desired signals. Handheld test equipment, in Which numer
ous electrical circuits are packaged in close proximity, is
particular susceptible to such signal noise and interference.
HoWever, many of the applications in Which the measure
ment of loW-voltage electrical signals in the sub-microvolt
range is required Would bene?t greatly from the use of
False positive results can be reduced in tWo Ways.
eters, and by combining different types of tests. Second,
bility is provided through the availability of an automated
screening auditory brainstem response (ABR) test capability
provided by the same device. Secondly, operational pro
cesses of a screening program can be improved through the
use of several onboard computer based expert systems.
These computer based expert systems provide improved
automatic interpretation of single test results, automatic
interpretation of multiple test results, and improved referral
processes through the matching of local referral sources With
various test outcomes, such as a referral to a speci?c type of
folloW-up, Whether it be a pediatrician, audiologist, oto
laryngologist, or a nurse. The device disclosed hereinafter
integrates in a single, hand-held device, a single stimulus
transducer, a single processor and a single softWare appli
cation for otoacoustic emission (OAE) and ABR testing.
portable, self-contained, hand-held test instruments.
[0009] An auditory abnormality is not a single, clearly
[0005] For example, universal neonatal auditory screening
de?ned entity With a single cause, a single referral source
programs have expanded greatly because of improved audi
tory measurement capability, improved rehabilitation strat
egies, increased aWareness of the dramatic bene?ts of early
and a single intervention strategy. The peripheral auditory
system has three separate divisions, the external ear, the
middle ear, and the sensorineural portion consisting of the
intervention for hearing impaired babies, and changes in
governmental policies. Current neonatal auditory screening
inner ear or cochlea, and the eight cranial nerve. Abnormali
ties can and do exist independently in all three divisions and
approaches, hoWever, do not account adequately for the
many different types and degrees of auditory abnormalities
that are encountered With present screening approaches.
these individual abnormalities require different intervention
and treatment. Prior art physical and operational character
Because of this, individual screening tests based on a single
measurement can be in?uenced negatively by interaction
can interact negatively to increase the total cost of an
among various independent auditory abnormalities.
the cost of each screening test though this is not the only
[0006] Current screening approaches have not considered
usually is resolved With an expensive full diagnostic test
adequately the entire screening program including:
physi
cal characteristics of the measurement device i.e., portabil
ity, physical siZe and ease of use, (ii) operational character
istics of the device i.e., battery life, amount of record
storage, required operating training, etc. and/or (iii) program
logistics i.e., retesting mechanisms, referral mechanisms,
record processing, patient tracking, report Writing, and other
practical aspects. These factors can interact negatively to
increase the total cost of an auditory screening program,
including the primary economic cost of screening, testing,
the secondary economic cost of additional testing, and
istics of devices and their in?uences on program logistics
auditory screening program. The primary economic cost is
economic cost. Ascreening test failure is called a “refer” and
scheduled several Weeks after hospital discharge, resulting
in signi?cant economic cost. A substantial portion of these
costs is unnecessary if the screening false positive rate is
high. Non economic costs include parental anxiety for false
positive screening results, unfavorable professional percep
tion of program effectiveness for programs With high false
positive rates and even inappropriate professional interven
tion because of misleading screening results.
[0010] The intervention of multiple measurements into a
single hand-held instrument alloWs for very important neW
Mar. 25, 2004
US 2004/0059250 A1
functionality not available With existing neonatal auditory
screening devices. This functionality includes (1) detection
of common external and middle ear abnormalities; (2) the
detection of less common sensorineural hearing loss asso
ciated With outer hair cell abnormalities, and (3) the detec
tion of even less common sensorineural hearing loss asso
ciated With inner hair cell or auditory nerve abnormality.
Moreover, the device disclosed hereinafter has the potential
to improve the accuracy and reliability of OAE measure
ments, to alloW for optimal interpretation of both the OAE
and ABR results, and to improve the referral process.
[0011] Attempts have been made in the past to provide the
detect less common sensorineural hearing loss associated
With outer hair cell abnormalities and the detection of less
common sensor hearing loss associated With inner hair cell
abnormalities. In the preferred embodiment, the device
includes a portable hand-held enclosure containing a digital
signal processor. The processor has a computer program
associated With it, capable of conducting both otoacoustic
emission test procedures and auditory brainstem response
test procedures for a test subject. A display device is
mounted to the enclosure, and displays patient information,
auditory screening setup procedures, and auditory screening
test results, including graphical analysis. The enclosure
includes a connection point for a probe, the connection point
capabilities provided by the present invention. In particular,
US. Pat. Nos. 5,601,091 (’091) and 5,916,174 (’174) dis
being operatively connected to the signal processor. The
close audio screening apparatus Which purport to provide a
hand-held portable screening device. HoWever, the screen
ing device disclosed in those patents is used in conjunction
With a conventional computer, and requires a docking station
[0015] The foregoing and other objects, features, and
device also includes an onboard poWer supply, making the
device completely self contained.
advantages of the invention as Well as presently preferred
for full application use. In no Way does the disclosure of
either patent provide a hand-held device that can be used
embodiments thereof Will become more apparent from the
independently of any other computer. That is to say, the
invention disclosed hereinafter provides a device of signi?
accompanying draWings.
reading of the folloWing description in connection With the
BRIEF DESCRIPTION OF THE SEVERAL
VIEWS OF THE DRAWINGS
cantly reduced siZe i.e., hand-held, Which is capable of
providing OAE and ABR testing. It can be operated in a
stand-alone mode, independently of any other computer
connection, if desired. The device includes a patient data
base, With names, and full graphic display capability. The
device also preferably is provided With a Wireless infrared
and an RS 232 connection port to provide output directly to
printers or to a larger database Where such is required. The
’174 and ’091 patents also operate on a linear averaging
[0016] In the accompanying draWings Which form part of
the speci?cation:
[0017] FIG. 1 is a top plan vieW of one illustrative
embodiment of an electrical testing device of the present
invention;
[0018]
FIG. 2 is a vieW in end elevation of the electrical
method to remove background noise. While such method
testing device;
Works Well for its intended purposes, use of a linear aver
[0019]
aging method is time consuming.
FIG. 3 is a vieW in end elevation of the electrical
testing device end opposite to that shoWn in FIG. 2;
[0012] Accordingly, there is a need for portable, hand-held
[0020]
test equipment capable of accurately measuring loW voltage
trical testing device shoWn in FIG. 1;
electrical signals in the sub-microvolt range, and Which is
capable of providing improved signal reliability in a reduced
time frame using an on-board processor to access and store
information in an associated memory storage device.
[0021]
FIG. 4 is a block diagrammatic vieW of an elec
FIG. 5 is a block diagrammatic vieW of a second
set of generic electrical input and output channels shoWn in
FIG. 4;
[0022]
BRIEF SUMMARY OF THE INVENTION
[0013] Brie?y stated, an effective sub-microvolt electric
testing device is provided. In the preferred embodiment, the
device includes a portable hand-held enclosure containing a
digital signal processor. The processor has a memory and a
computer program associated With it for control of CODEC
components capable of generating sub-microvolt electrical
output signals on four discrete output channels and for
receiving sub-microvolt electrical input signals on four
discrete input channels. A display device is mounted to the
enclosure, and displays test information, test setup proce
dures, and test results including the graphing of test results.
The enclosure includes a connection point for one or more
probes, the connection point being operatively connected to
FIG. 6 is a block diagrammatic vieW of an auditory
screening embodiment of the electrical testing device shoWn
in FIG. 1;
[0023] FIG. 7 is a block diagrammatic vieW of the
DPOAE interface in FIG. 6;
[0024] FIG. 8 is a block diagrammatic vieW of the ABR
interface in FIG. 6;
[0025] FIG. 9 is a block diagrammatic vieW of the signal
output phase of the OAE testing employed With the device
of FIG. 6;
[0026] FIG. 10 is a block diagrammatic vieW of the signal
input phase of the OAE testing employed With the device of
FIG. 6;
the digital signal processor. The device also includes an
[0027]
onboard poWer supply, making the device completely self
sponding parts throughout the several ?gures of the draW
contained.
Corresponding reference numerals indicate corre
ings.
effective auditory screening device is provided. The inte
DESCRIPTION OF THE PREFERRED
EMBODIMENT
gration of an OAE screening device and ABR screening
[0028] The folloWing detailed description illustrates the
device into a single, hand-held instrument enables a user to
invention by Way of eXample and not by Way of limitation.
[0014]
In one embodiment of the present invention, an
Mar. 25, 2004
US 2004/0059250 A1
The description clearly enables one skilled in the art to make
and use the invention, describes several embodiments, adap
tations, variations, alternatives, and uses of the invention,
including What is presently believed to be the best mode of
carrying out the invention.
[0029]
Referring noW to FIG. 1 through FIG. 3, reference
digital signal processor 40 performs the functions of the
separate micro-controller in addition to signal processing,
eliminating the requirement of a separate micro-controller,
resulting in substantial savings in circuit board space, manu
facturing cost and operational poWer consumption.
numeral 10 illustrates one embodiment of the hand-held
[0034] To reduce undesired signal interference during the
data-acquisition phase of operations, the processor 40 in
sub-microvolt electrical signal measurement device of the
device 10 is either shut-doWn or sWitched to a “sleep” mode
present invention. The measurement device 10 includes an
purposes of illustration and not for limitation, measures 7%“
during data collection operations, Which can be carried out
independently of the processor 40. Further reduction in
external signal noise is achieved by the execution of soft
long by 3%“ Wide by 11/2“ deep. It is important to note that
Ware in data and program memory 40M internal to processor
the device 10 can be carried by the user Without compro
40, thereby eliminating external bus access signal noise.
mise, and truly represents a portable hand-held device
having full functionality as described beloW. The device 10
[0035] A memory subsystem 42 is operatively connected
enclosure 12, Which in the preferred embodiment, and for
includes a keyboard 14 and an LCD display 16. One or more
LED indicators are optionally included, such as an LED
pass/refer indicator 18, and an LED AC charging indicator
20. Again, by Way of illustration and not by limitation, it
should be noted that the LCD display 16 measures, in the
to the processor 40. The memory subsystem 42 includes a
random access memory (RAM) 42A for storing intermediate
results and holding temporary variables, and a ?ash memory
42B for storing non-volatile, electrically programmable
preferred embodiment, approximately, 2“ by 33/8“. The mea
variables, test result data and system con?guration informa
tion. In the embodiment illustrated, the ?ash memory 42B is
surement is not necessarily important, except to shoW that
the LCD display 16 is fully functional for a user, and the
device 10 can operate independently of any other computer
con?gurations ?les.
system.
[0036] Amemory mapped input/output device 44 is opera
[0030]
In the embodiment illustrated, the enclosure 12
also houses an infrared port 22, and a compatible RS-232
port 24, a probe connection 26 suitable for use With an input
probe 28, such as an ear probe, and an interface 30 for a
substantially oversiZed, enable the device 10 to accommo
date several hundred data records, as Well as multiple
tively connected to the memory subsystem 42 and to the
digital signal processor 40. The memory mapped input/
output 44 in turn is operatively connected to the LCD
display 16, the keyboard 14, an output LED indicator 18 and
plurality of output electrodes 32. The electrodes 32 are
a real time clock 46.
shoWn attached to a conventional carrier 34. Probe 28 is
[0037] The LCD display 16 provides the user With a
display array preferably having a minimum siZe of 128x256
pixels. A display array of this siZe is suf?cient to present full
Waveforms of signal tests conducted by the device 10. The
device 10 enables the LCD 16 to present signal information
conventional and is not described in detail. Suitable probes,
such as ear probes, are commercially available from Ety
motic Research, Part Nos. ER-10C, ER-10D, and GSI
2002-3250, for example.
to a user graphically in real time on the device 10 itself,
[0031] Referring noW to FIG. 4, a block diagram vieW of
the hand-held sub-microvolt electrical signal measurement
device 10 is shoWn and described. Preferably, the system
shoWn in FIG. 4 is manufactured on a single printed circuit
the quality of the data, signal amplitudes, signal frequency,
board, With mixed signal design for both analog and digital
operation. The device 10 preferably is loW poWered, and
generally operates at 3.3 volts, except for the LCD display
[0038] The keyboard 14 preferably is a membrane sWitch
keyboard, Which incorporates only the minimum keys nec
16 and some loW poWer portions of the analog circuitry
employed With the device 10. To reduce undesired signal
interference, it has been found that it is preferable that all
analog and digital circuit components share a common
electrical ground point Within the device 10.
[0039] The real-time clock 46 is operatively connected to
the processor 40 through the memory mapped input/output
complemented With textual and numeric information about
noise ?oors and other related signal information.
essary for operation of the device 10. All keys are program
mable, except for an On/Off key 15.
device 44. The real-time clock 46 enables the processor 40
to provide a time stamp for each data collection or test
[0032] Asuitable micro-processor 40 is the control for the
device 10. In the preferred embodiment illustrated, the
processor 40 is a Motorola model No. 56303 digital signal
processor, hoWever, those of ordinary skill in the art Will
recogniZe that any suitable micro-processor or micro-con
troller having suf?cient computational poWer and speed may
be utiliZed. All signal processing functions described here
performed.
inafter are performed by the processor 40, as Well as the
addition, graphic functions, user interface functions, data
strength at or above a minimum value. The output LED 18
further alloWs the use of the device 10 in loW light areas,
Where the LCD display 16 may be dif?cult to read or
storage functions, and other device functionality are con
interpret.
control of all input and output functions of the device 10. In
trolled by the processor 40.
[0040]
The output LED 18 is used to convey test results to
non-trained users to avoid confusion or misinterpretation of
the LCD graphics display 16. For example, the processor 40
may be programmed to illuminate the output LED 18 When
a set of predetermined input criteria, such as a signal
[0033] In conventional design logic, the digital signal
[0041] The plurality of analog to digital/digital to analog
coder/decoders 48 (codecs 48) are operatively connected to
processor 40 is used for signal processing, and a separate
micro-controller is used for device control. In device 10, the
the signal processor 40 along a dedicated serial link. As Will
be appreciated by those skilled in the art, the codecs 48 are
Mar. 25, 2004
US 2004/0059250 A1
special integrated circuit chips that perform analog to digital
operatively associated With a one or more input/output
programming of the processor 40 from a personal computer,
for eXample, and is intended for use only for initial softWare
doWnload and major softWare program upgrades of the
devices interfaces 52, Which provide the functionality of the
processor 40.
and digital to analog conversion. The codecs 48 in turn are
device 10 under control of the processor 40. Preferably, the
digital signals generated and received by codecs 48 have
20-bit resolution for both analog to digital and digital to
analog conversions.
[0042] In one embodiment of the present invention 10,
input/output interface 52 includes four input channels and
four output channels adapted for sub-microvolt electrical
signals. As shoWn in FIG. 5, the input/output interface 52
[0048]
Referring noW to FIG. 6, a block diagram vieW of
one embodiment of the device 10, con?gured for use as an
auditory screening device 200, is shoWn and described. The
device 200 contains OAE and ABR simulator capabilities in
a single, hand-held package. Preferably, the system shoWn in
FIG. 6 is manufactured on a single printed circuit board,
With miXed signal design for both analog and digital opera
Speci?cally, signals received from each input channel 32 are
routed through an electrical insulator circuit 52A, consisting
of a plurality of metal oXide varistors, resistors, and capaci
tion. The device 200 preferably is loW poWered, and gen
erally operates at 3.3 volts, eXcept for the LCD display 216
and some loW poWer portions of the analog circuitry
employed With the device 200. To reduce undesired signal
interference, it has been found that it is preferable that all
analog and digital circuit components share a common
electrical ground point Within the device 200.
tors, Which function as surge arrestors to isolate the input
channels 32 from any dangerous electrical currents or volt
ages. The insulator circuit 52A functions to replace conven
[0049] A digital signal processor 240 is the control for the
device 200. In the preferred embodiment illustrated, the
consists of a plurality of analog signal processing chips, not
shoWn individually, Which ?lter and amplify the signals
received from a number of discrete input channels 32.
tional insulator circuits Which utiliZe optical signal path
Ways, thereby eliminating the associated signal noise
resulting from the conversion betWeen electrical signals and
processor 240 is a Motorola model No. 56303 DSP. All
signal processing functions described hereinafter are per
formed by the processor 240, as Well as the control of all
coupled differential operational ampli?er 52C having high
input and output functions of the device 200. In addition, the
graphic functions, user interface, patient data storage func
tions and other device functionality are controlled by the
processor 240. In conventional design logic, the digital
signal processor 240 is used for signal processing, and a
separate micro controller is used for device control. In
gain. A common mode cancellation ampli?er 52D is
included in the input/output interface 52 to further reduce
functions of the separate micro controller in addition to
optical signals.
[0043] Signals from the input channels 32 are then routed
through a sWitching netWork 52B, Wherein an individual
signal is automatically selected and passed to a capacitive
signal noise levels. The resulting ampli?ed signal is then
device 200, the digital signal processor 240 performs the
routed to the codecs 48. In addition to selecting an individual
signal processing, eliminating the requirement of a separate
microprocessor, resulting in substantial savings in circuit
signal from the input channels 32, the sWitching netWork
board space, manufacturing cost and operational poWer
52B permits a variety of signal measurements on the input
channels 32 to be carried out using the same differential
consumption. To reduce undesired signal interference during
the data-acquisition phase of operations, the processor 240
operational ampli?er 52C, by altering the ampli?er gain
setting.
in device 200 is either shut-doWn or sWitched to a “sleep”
mode during data collection operations, Which can be car
[0044] Returning to FIG. 4, a mode con?guration system
54, a reset Watchdog system 56, a clock crystal 58, a poWer
ried out independently of the processor 240. Further reduc
tion in external signal noise is achieved by the eXecution of
supply 60, preferably a nickel-metal hydride battery, and a
battery charger 62 all are also positioned Within the enclo
processor 240, thereby eliminating eXternal bus access sig
sure 12 and operatively connected to the processor 40. While
softWare in data and program memory 240M internal to
nal noise.
each of these blocks is required for operation of the device
[0050] A memory subsystem 242 is operatively connected
10, they are standard in nature and are not described in
detail.
to the processor 240. The memory subsystem 242 includes
a random access memory (RAM) 242A for storing interme
diate results and holding temporary variables, and a ?ash
[0045]
The processor 40 has an input-output channel 64,
Which preferably includes an infrared connection 22, a
?ber-optic connection 23 and an isolated RS-232 interface
24. The device 10 can communicate With any infrared
compatible or RS-232 compatible personal computer,
printer, or other digital device (not shoWn) for data trans
memory 242B for storing non-volatile, electrically program
mable variables, patient data, and con?guration information.
In the embodiment illustrated, the ?ash memory 242B is
substantially oversiZed, enable the device 200 to accommo
date several hundred full patient records, as Well as multiple
mission. Data transmission may include test subject infor
con?gurations ?les.
mation, con?guration data for the signal processor 40, or
softWare program updates for storage in the memory sub
system 42.
operatively connected to the memory subsystem 242 and to
[0046] A audio output 66 in the form of a buZZer also is
provided. The audio output 66 provides an audio feedback to
the user for keyboard actions and an audio indication for
display 216, the keyboard 214, the pass/referral LED indi
error conditions.
[0047] Aserial port 68 also is operatively connected to the
processor 40. The serial port 68 is utiliZed to provide direct
[0051] A memory mapped input/output device 244 is
the digital signal processor 240. The memory mapped input/
output 244 in turn is operatively connected to the LCD
cator 218 and a real time clock 246.
[0052] The LCD display 216 provides the user With a
display array preferably having a minimum siZe of 128x256
pixels. A display array of this siZe is suf?cient to present full
Mar. 25, 2004
US 2004/0059250 A1
Waveforms of audiometric tests conducted by the device
200. The device 200 enables the LCD 216 to present signal
234 are routed through an electrical insulator circuit 252A,
information to a user graphically in real time on the device
and capacitors, Which functions to isolate the electrodes 234
from any dangerous electrical currents or voltages. The
insulator circuit 252A functions to replace conventional
200 itself, complemented With textual and numeric infor
mation about the quality of the data, signal amplitudes,
signal frequency, noise ?oors and other related signal infor
mation.
[0053] The keyboard 214 preferably is a membrane sWitch
keyboard, Which incorporates only the minimum keys nec
essary for operation of the device 200. All keys are pro
grammable, eXcept for an On/Off key (not shoWn).
[0054] The real-time clock 246 is operatively connected to
the processor 240 through the memory mapped input/output
consisting of a plurality of metal oXide varistors, resistors,
insulator circuits Which utiliZe optical signal pathWays,
thereby eliminating the associated signal noise resulting
from the conversion betWeen electrical signals and optical
signals. Signals from the electrodes 234 are then routed
through a sWitching netWork 252B, Wherein an individual
signal is automatically selected and passed to a differential
operational ampli?er 252C. A common mode cancellation
ampli?er 252D is included in the ABR interface 252 to
further reduce signal noise levels. The resulting ampli?ed
device 244. The real-time clock 246 enables the processor
240 to provide a time stamp for each patient and test
performed, as Well as providing time signals for internal
signal is then routed to the codecs 248.
operation of the device 200.
ning With the eighth cranial nerve and sequentially through
[0055]
neurons in the auditory pathWays in the central nervous
system from the brainstem to the cortex. Through the
The LED pass/refer diode 218 is used to convey
test results to non-trained users, namely a nurse as opposed
to an audiologist or otolaryngologist. Use of the LED 218
[0059]
In this mode of operation, the ear is presented With
a repeated acoustic stimuli that cause neurons to ?re begin
mechanism of volume conduction, the electrical potentials
generated from these neuronal ?rings can be detected by the
avoids confusion or misinterpretation of the LCD graphics
display 216, and alloWs use of the device 200 in loW light
areas, Where the LCD display 216 may be dif?cult to
electrodes 232 on the surface of the skin.
interpret.
to provide automated impedance check of the placement of
[0056] The plurality of analog to digital/digital to analog
coder/decoders 248 (codecs 248) are operatively connected
to the signal processor 240 along a dedicated serial link. As
Will be appreciated by those skilled in the art, the codecs 248
are special integrated circuit chips that perform analog to
digital and digital to analog conversion. The codecs 248 in
[0060]
An additional function of the ABR interface 252 is
electrodes 232. Once the electrodes 232 are in place, a small
current is injected through the electrodes 232 into the scalp
of the subject, and the impedance betWeen electrodes 232 is
measured. In addition to selecting an individual signal from
the electrodes 234, the sWitching netWork 252B permits
impedance measurements of the electrodes 234 to be carried
turn are operatively associated With a plurality of input/
out using the same differential operational ampli?er 252C,
output devices, Which provide the functionality of the device
by altering the ampli?er gain setting. Impedance can be
200 under control of the processor 240.
varied by placement of the electrodes. Once the impedance
is Within the predetermined range for operation, ABR signal
[0057] An otoacoustic emission interface 250 (DPOAE
UP) is operatively connected to the signal processor 240
connection can begin. It is important to note that impedance
checking can be accomplished Without unplugging the elec
trodes. That is to say, checking is automatic.
through the associated codecs 248. The otoacoustic emission
interface 250 preferably is a loW noise, differential analog
circuit With high common mode noise rejection. As shoWn
in FIG. 7, the otoacoustic emission interface 250 is intended
to drive tWo sound transducers 251R, 251L through a pair of
differential operational ampli?ers 250A, 250B to produce a
variety of signals, from pure tones at various frequencies to
chirps, clicks, sine Waveforms, etc. The otoacoustic emis
and a battery charger 262 all are operatively connected to the
processor 240. While each of these blocks is required for
operation of the device 200, they are standard in nature and
sion interface 250 can present tones at standard sound
are not described in detail.
pressure levels. The device employed With the otoacoustic
emission interface 250 includes a microphone 251M, also
inserted in the ear canal, Which collects signals coming back
from the ear, and provides suf?cient linear ampli?cation
through a dual-stage ampli?er 250C to present the signals to
the codecs 248. The transducers and microphone interface
circuits include a plurality of electrostatic discharge diodes
and induction coils to provide electrical shock protection
250D. In various embodiments of this invention, the otoa
coustic emission interface 250 also can be used for otore
?ectance measurements for assessing some middle ear con
ditions.
[0058] The ABR interface 252, shoWn in FIG. 8, consists
of a plurality of analog signal processing chips, not shoWn
individually, Which ?lter and amplify the signals received
from the scalp of a subject via electrode Wires 232. Speci?
cally, signals received from each of the individual electrodes
[0061] Returning to FIG. 6, a mode con?guration system
254, a reset Watchdog system 256, a clock crystal 258, a
poWer supply 260, preferably a nickel-metal hydride battery,
[0062]
The processor 240 has an input-output channel
264, Which preferably includes infrared connection 22,
?ber-optic connection 23 and isolated RS-232 interface 24.
The device 200 can communicate With any infrared com
patible or RS-232 compatible personal computer, printer, or
other digital device (not shoWn) for data transmission. Data
transmission may include patient information, con?guration
data for the signal processor 240, or softWare program
updates for storage in the memory subsystem 242.
[0063] A audio output 266 in the form of a buZZer may be
provided. The audio output 266 provides an audio feedback
to the user for keyboard actions and an audio indication for
error conditions.
[0064] A serial port 268 also is operatively connected to
the processor 240. The serial port 268 is utiliZed to provide
direct programming of the processor 240 from a personal
Mar. 25, 2004
US 2004/0059250 A1
computer, for example, and is intended for use only for
initial software download and major softWare program
upgrades of the processor 240.
[0065] As an auditory screening device 200, the present
invention utiliZes a auditory phenomena knoWn as a distor
the test frequencies. Should a combination of frequencies be
required for Which no common integer number can be found
to ?t in a practical siZe frame, the frame siZe is adjusted to
jdp and the frame is WindoWed prior to Fourier Transforma
tion, but this method is used only in extreme cases since in
normal operation, the required frequencies are available.
tion product otoacoustic emission (DPOAE). ADPOAE is a
tone generated by a normal ear in response to the application
of tWo external tones. When tWo tones, f1 and f2 are applied
[0071] The data from a single frame is passed to a point
Discrete Fourier Transform (DFT) block 284 Which calcu
to an ear, the normal non-linear outer hair cells generate a
lates the signal’s magnitude and phase content, but only at
third tone fdp, Which is called a distortion product. The
distortion product fdp then propagates from the outer hair
frequencies of interest, including f1, f2, and fdp to determine
cells back to the ear canal Where it is emitted. The level of
DFT to reduce edge effects, although WindoWing induces
the DPOAE can be used as a measure of outer hair cell
function. If the outer hair cell system is absent or otherWise
energy at other bands. The block 284 is used only for
temporary calculations, and the WindoWed data is not reused
not functioning properly, the non-linearity Will be absent or
reduced and the fdp Will either not be generated or generated
again. The output of block 284 is the magnitude and phase
of primary signals at f1 and f2 and the noise ?oor ?gure of
at a loWer than expected level.
time at fdp. The output of block 284 forms an input to frame
rejection block 286 and to an on-line calibration calculation
block 288.
[0066] The measured DPOAE is highly dependent upon
the speci?c tones that invoke it. The frequencies of f1 and f2,
and their respective levels in the ear canal, L1 and L2 must
be controlled precisely. Under knoWn signal conditions, the
largest distortion product fdp is generated at a very speci?c
frequency (fdP=2f1—f2), and level Ldp. Comparison of the
level of Ldp With knoWn values from individuals With normal
outer hair cell systems forms the basis of the decision of
Whether the patient either passed the screening, illuminating
a noise ?oor. WindoWing is induced prior to processing the
[0072] With the information on the magnitudes at various
frequencies, a noise calculation algorithm is employed at
and/or around fdp to determine the noise ?oor. The magni
tude of the noise ?oor and frequency content are used
against a set of predetermined conditions ie a comparison
against an empirically derived table contained in the pro
cessor 240, to determine the outcome of the frame. That
the pass/refer LED 218, or requires a referral for a more
outcome has three distinct possibilities. First, if the noise
complete diagnostic testing.
magnitude and frame content exceed a multi-threshold con
[0067]
Signals other than pure tones can be presented to
the ear, Which Will also evoke an auditory response from the
ear, such as clicks, chirps, etc. The DPOAE response is used
With the auditory screening device 200 as an example of one
such input. Other auditory stimuli generating an auditory
response Would be processed by the auditory screening
device 200 the same Way as the DPOAE.
[0068] As shoWn in FIG. 6, during operation, the proces
sor 240 sends a ?ltered output signal from a ?lter 268
through the digital to analog converter portions 270 of the
codecs 248. The output signals are then routed through
ampli?er components 250A and 250B in the DPOAE inter
face 250 and transmitted to the output components 251R and
251L of the ear probe 228 utiliZed in conjunction With the
device 200.
[0069] As shoWn in FIG. 7, the ear probe 228 includes a
microphone 270 Which returns signals through a second
ampli?er 250C in the DPOAE interface 250. The ampli?ed
analog signal is routed through an analog-to-digital con
verter 280 in the codecs 248, and conveyed to the processor
240.
[0070] In the processor 240, the incoming analog signal is
sampled using a frame buffer 282. The siZe of each neW
frame in the frame buffer 282 is calculated to be an integer
number of samples of the tWo primary tones at frequencies
f1 and f2 and also, an integer number of samples of the
otoacoustic tone produced by the ear at fdp. This is a critical
step to assure quality of subsequent signaling processing, by
avoiding WindoWing techniques, Which can introduce sub
stantial artifacts. Tables of numbers for each standard fre
dition at measured frequency bands, the neW frame is
rejected. Second, if the noise magnitudes fall betWeen a set
of reject thresholds and a set of accept thresholds, the data
in the frame is disregarded, but the noise information is kept
to update the noise level average. Third, if the noise mag
nitudes are beloW the accept thresholds, the frame is kept
and passed on for further processing and the noise magni
tudes are averaged together With the noise average of the
previous frame. This information is used to update thresh
olds, such that the system adapts to environmental condi
tions.
[0073] When the information about magnitudes of pri
mary tones at f1 and f2, and the noise ?oor information at
and/or around fdp, an online calibration of the level of
magnitudes takes place. Several actions occur in the cali
bration block 288. First, if the noise ?oor is large When no
primary tones are present, the frequency of the primaries is
adjusted Within predetermined limits. A neW fdp is calcu
lated, and the noise content of frequency bins at and around
fdp is checked again. This process is repeated until a stable,
loW noise ?oor is established. No primary tones are played
through the speaker through this process. Once the primaries
are presented, they are stepped up to the full output ampli
tude, as programmed by the user and calibrated in the ear by
increasing the output of the codecs 248. No data collection
from the ear has taken place yet. At this time, if the level is
not reached in a user predetermined time, and at the rate of
increase of the primaries, the test is aborted due to lack of
?t or the loW quality of ?t of the probe in the ear canal.
[0074]
Once a proper ?t of the probe in the ear canal is
achieved, and testing begins, data collection takes place.
quency employed in the device 200 and for other frequen
During the entire process of data collection, the levels of
cies in use or intended use in the device 200 are available,
tones at f1 and f2 are checked to ensure that they remain
and are programmed into the algorithm once the user selects
Within predetermined limits throughout the test. If they
Mar. 25, 2004
US 2004/0059250 A1
exceed those limits, the output is adjusted up or doWn to
compensate until a maximum compensation limit is reached,
at Which time, the test is aborted and the user is noti?ed.
Also, the magnitude at and/or around fdp is continuously
monitored to assure loW noise ?oor, and if necessary, the
frequency of the primary tones are adjusted on-line Within
predetermined limits to avoid the high external noise region.
The change in frequencies of the primaries is minimal, and
Within the speci?ed tolerances of the device 200, and have
been shoWn not to affect the magnitude of the tone Within the
ear at fdp.
[0075] The block 290 is a store/copy buffer. As a frame of
signal data is collected in neW frame buffer 282, a copy of
it is saved by the store/copy buffer 290 for processing of the
subsequent frames. The store/copy buffer 290 receives frame
data from neW frame buffer 282 and has a variable depth,
depending the number of frames averaged together. Buffer
290 provides an output to a slide buffer block 292 and an
average buffer 294. The slide buffer 292 operates With the
stored previous frames, Which are slid by a predetermined
amount and the empty spaces padded With Zeros for subse
quent processing in the average buffer 294.
in ?lter 298 Which removes any remaining high or loW
frequency components not required for ?nal data presenta
tion.
[0080]
The averaged and ?ltered data is converted to
frequency domain, in the embodiment illustrated, by using a
discrete Fourier Transform at block 300, and the resulting
data then is ready for presentation to an operator as indicated
at block 302. As Will be appreciated by those skilled in the
art, other signal processing methods are available to convert
data, and those other methods are compatible With the device
200.
[0081]
In further alternate embodiments of the present
invention 10, utiliZed as vibration detectors or alcohol
intoximeters, the input/output interface 52 is replaced With,
or coupled to, one or more suitable electrical signal sensors
con?gured to measure signals representative of the desired
test material, for example, a vibration Waveform or an
electrical signal representative of breath alcohol content.
[0076] In the average buffer 294, the frames are averaged
together to reduce the uncorrelated noise present. Theoreti
[0082] In vieW of the above, it Will be seen that the several
objects of the invention are achieved and other advantageous
results are obtained. As various changes could be made in
the above constructions Without departing from the scope of
the invention, it is intended that all matter contained in the
above description or shoWn in the accompanying draWings
cally, the noise is reduced by a factor of one over the square
shall be interpreted as illustrative and not in a limiting sense.
root of the number of averaged frames, i.e.:
1. A sub-microvolt electrical signal testing device, com
l
\/No.Avg.Frames .
prising:
a portable hand-held enclosure;
a processor housed by said enclosure;
[0077]
The frames are averaged in a linear fashion, sample
by sample and a neW frame is created at the end of the
averaging operation. The advantage of this method is that
a memory operatively coupled to said processor, said
memory storing one or more operating instructions;
the data is essentially correlated against a slid copy of itself,
slid far enough aWay to avoid averaging the same informa
a display device mounted to said enclosure, said display
device being operatively connected to said processor;
tion content. This provides either a substantial reduction in
uncorrelated noise energy for the same amount of sampling
time or a substantial reduction in sampling time to obtain the
an multi-channel input-output interface operatively
coupled to said processor, said multi-channel input
output interface con?gured to receive external sub
microvolt electrical signals; and
equivalent noise reduction When compared to standard linear
averaging.
Wherein said processor is con?gured to utiliZe said one or
[0078]
The minimum limit to the sliding of the data, and
more operating instructions to perform one or more
to the reuse of old data frame is the autocorrelation function
of the data in the frame, Which can be predetermined or
tests on signals received from said multi-channel input
output interface, and to display results of said one or
calculated on-line. This method is equivalent to taking much
smaller frames and averaging them together. HoWever, for
the purposes of the subsequent Fourier Transformations and
?ltering taking place, the frame siZe is required to be large
(i.e., 960 samples at 48 kilohertZ sampling rate), to obtain
several full cycles of each of the tones at f1, f2, and fdp. The
problem With taking a large number of very small frames is
that the Fourier Transforms or other signal processing meth
more tests on said display device.
2. The sub-microvolt electrical signal testing device of
claim 1 further including:
a bi-directional communications channel operatively con
nected to said multi-channel input-output interface and
to said processor to communicate said external electri
cal signals.
3. The sub-microvolt electrical signal testing device of
ods require several cycles of data for proper operation. The
method of the present invention outperforms standard linear
averaging of large frames because of the reduction in time
claim 2 Wherein said bi-directional communications channel
has a 20-bit signal resolution.
as Well as providing proper operation of the Fourier Trans
forms.
4. The sub-microvolt electrical signal testing device of
claim 2 Wherein said mutli-channel input-output interface
[0079]
The ?nal average buffer 296 obtains the averaged
data from the average buffer 294, and collects it in a buffer
that is used for subsequent processing and signal statistics.
The output of the ?nal average buffer 296 is digitally ?ltered
includes one or more input channels;
a plurality of electrical shock protection components
coupled betWeen said at least one input channel and
said bi-directional communications channel;
Mar. 25, 2004
US 2004/0059250 A1
a switching network coupled between each of said plu
rality of electrical shock protection components and
said bi-directional communications channel, said
switching network con?gured to selectively couple one
of said plurality of electrodes to said bi-directional
communications channel; and
a differential operational ampli?er coupled between said
switching network and said bi-directional communica
tions channel, said differential operational ampli?er
having an adjustable gain setting.
5. The sub-microvolt electrical signal testing device of
claim 4 wherein said differential operational ampli?er is
coupled between said switching network and said bi-direc
tional communications channel by one or more capacitors.
an auditory brain stem testing interface operatively
coupled to said processor.
12. The auditory screening device of claim 11 including
said processor having an internal memory, said processor
con?gured to utiliZe said internal memory to eXecute said
computer program, whereby signal noise levels from exter
nal bus access are reduced.
13. The auditory screening device of claim 11 wherein
said otoacoustic emission testing interface comprises:
at least one output channel con?gured to receive signals
from said processor;
at least one transducer operatively connected to said at
least one output channel;
6. The sub-microvolt electrical signal testing device of
claim 4 wherein said mutli-channel input-output interface
at least one differential operational ampli?er coupled
includes a common mode cancellation ampli?er con?gured
between said at least one output channel and said at
least one transducer; and
to reduce signal noise levels in said electrical signals.
7. The sub-microvolt electrical signal testing device of
claim 1 wherein said multi-channel input-output interface
includes an otoacoustic emission testing interface and an
auditory brain stem testing interface; and
wherein said processor is con?gured with said one or
more stored operating instructions for auditory tests
selected from the group comprising otoacoustic emis
sion test procedures, auditory brainstem response test
procedures, and combinations thereof for a test subject.
8. The sub-microvolt electrical signal testing device of
claim 1 wherein said multi-channel input-output interface
includes an vibration testing interface; and
wherein said processor is con?gured to utiliZe said one or
more stored operating instructions to eXtract vibration
information from said signals.
9. The sub-microvolt electrical signal testing device of
claim 1 wherein said multi-channel input-output interface
includes an alcohol intoXimeter interface; and
wherein said processor is con?gured to utiliZe said one or
more stored operating instructions for calculating alco
hol levels from said signals.
10. The sub-microvolt electrical signal testing device of
claim 1 further including said processor having an internal
memory, said processor con?gured to utiliZe said internal
memory to eXecute said one or more operating instructions,
whereby signal noise levels from eXternal bus access are
reduced.
wherein said at least one transducer is adapted to convert
said received signals into acoustic signals selected from
the group comprising pure tones, chirps, clicks, and
sine waveforms audible to a human ear.
14. The auditory screening device of claim 11 wherein
said auditory brain stem testing interface comprising:
a plurality of electrodes, each of said electrodes adapted
to receive eXternal electrical signals;
a bi-directional communications channel operatively con
nected to said plurality of electrodes and to said pro
cessor to communicate said external electrical signals;
a plurality of electrical shock protection components
coupled between each of said plurality of electrodes
and said bi-directional communications channel;
a switching network coupled between each of said plu
rality of electrical shock protection components and
said bi-directional communications channel, said
switching network con?gured to selectively couple one
of said plurality of electrodes to said bi-directional
communications channel; and
a differential operational ampli?er coupled between said
switching network and said bi-directional communica
tions channel, said differential operational ampli?er
having an adjustable gain setting.
15. An otoacoustic emission testing interface comprising:
11. An auditory screening device, comprising:
a portable hand-held enclosure;
a processor housed by said enclosure, said processor
con?gured with a computer program operated on com
mand by a user, said computer program producing
auditory tests selected from the group comprising otoa
coustic emission (OAE) test procedures, auditory
at least one output channel;
at least one transducer operatively connected to said at
least one output channel;
at least one differential operational ampli?er coupled
between said at least one output channel and said at
least one transducer; and
brainstem response (ABR) test procedures, and com
binations thereof for a test subject;
a display device mounted to said enclosure, said display
device being operatively connected to said processor,
said display device displaying the results of the selected
test in real time;
an otoacoustic emission testing interface operatively
coupled to said processor; and
wherein said at least one transducer is adapted to produce
acoustic signals selected from the group comprising
pure tones, chirps, clicks, and sine waveforms to a
human ear.
16. The otoacoustic emission testing interface of claim 15
further comprising at least one electrical shock protection
component coupled between said at least one output channel
and said at least one transducer.
Mar. 25, 2004
US 2004/0059250 A1
17. The otoacoustic emission testing interface of claim 15
further comprising:
at least one input channel;
at least one microphone operatively connected to said at
least one input channel to receive signals from a human
ear; and
at least one dual-stage ampli?er coupled betWeen said at
least one input channel and said at least one micro
phone, said dual-stage ampli?er con?gured to provide
linear ampli?cation to said received signals.
18. The otoacoustic emission testing interface of claim 16
further comprising at least one electrical shock protection
component coupled betWeen said at least one input channel
and said at least one microphone.
19. An auditory brain stem testing interface comprising:
a plurality of electrodes, each of said electrodes adapted
to receive external electrical signals;
a bi-directional communications channel operatively con
nected to said plurality of electrodes;
a plurality of electrical shock protection components
coupled betWeen each of said plurality of electrodes
and said bi-directional communications channel;
a sWitching netWork coupled betWeen each of said plu
rality of electrical shock protection components and
said bi-directional communications channel, said
sWitching netWork con?gured to selectively couple one
of said plurality of electrodes to said bi-directional
communications channel; and
a differential operational ampli?er coupled betWeen said
sWitching netWork and said bi-directional communica
tions channel, said differential operational ampli?er
having an adjustable gain setting.
20. The auditory brain stem testing interface of claim 19
Wherein said plurality of electrical shock protection compo
nents includes at least one surge suppression component.
21. The auditory brain stem testing interface of claim 19
further comprising a common mode cancellation ampli?er
coupled betWeen said sWitching netWork and said differen
tial operational ampli?er, said common mode cancellation
ampli?er con?gured to reduce signal noise levels betWeen
said plurality of electrodes and said bi-directional commu
nications channel.
22. The auditory brain stem testing interface of claim 19
Wherein said differential operational ampli?er is con?gured
With a ?rst gain setting to amplify a signal from one of said
plurality of electrodes, and said differential operational
ampli?er is con?gured With a second gain setting to facili
tate impedance testing of said plurality of electrodes.
23. The auditory brain stem testing interface of claim 22
Wherein said sWitching netWork is further con?gured to
select betWeen said ?rst gains setting and said second gain
setting on said differential operational ampli?er.
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