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glottal enterprises
Two-Channel Electroglottograph
and
Microphone Amplifier
Model EG2-PCX
Glottal Enterprises, Inc.
1201 E. Fayette Street
Syracuse, New York 13210
USA
Phone:
Fax:
Internet:
(315) 422-1213
(315) 422-1216
www.glottal.com
glottal enterprises
EG2-PCX Manual
9/2006
INTRODUCTION
Electroglottography is an easy-to-use, non-invasive method of measuring the pattern of vocal fold contact
variation during voice production. The electroglottograph (EGG) measures the variations in the electrical
impedance of the neck at the level of the vocal folds caused by the variation of vocal fold contact as the
vocal folds vibrate. The method uses a pair of electrodes on the neck that apply a small, safe electrical
current, and measures the patterning of vocal fold contact area (VFCA).
The Glottal Enterprises EG2 two-channel electroglottographs record simultaneous EGG waveforms at two
neighboring neck locations. This patented innovation allows the user to easily verify correct electrode
placement and waveform accuracy. Using this multichannel approach not only makes the technique easier
to use and more reliable, but also can allow the quantitative measurement of vertical laryngeal movement
during voicing.
All EG2-series electroglottographs are battery operated and therefore portable as well as safe. These
units offer all of the features you would expect to find on an electroglottograph, as well as providing a few
unique ones. The Electrode Placement / Larynx Tracking indicator helps the operator determine the
optimum electrode placement without guesswork, while a signal-strength indicator indicates whether the
EGG signal is strong enough to be reliable.
INITIAL SETUP
The equipment and accessories listed below are provided by Glottal Enterprises:
1) EG2-PCX electroglottograph unit
2) EL-2 electrodes
3) Electrode Strap
4) Water soluble electrode gel
5) Battery charger
6) 3 foot USB cable
7) Cable having 1/8 mini-phone plugs on each end
8) High-quality electret (capacitance) microphone
The EG2-PCX can be connected to your computer using either the USB cable or the stereo output cable
having 1/8 mini-phone plugs on each end. The USB cable would be plugged into the USB jack on the rear
panel and the 1/8” phone plug cable would be plugged into the stereo, audio-style output jack on the rear
panel. The stereo output jack is wired so that the plug ‘tip’ is the audio (microphone) signal, and the ‘ring’
is the EGG signal. (For this reason, a mono plug will not show an EGG signal.) When connected to a
computer equipped with a sound card via a stereo cable, the left channel carries the audio (microphone)
signal, and the right channel the EGG.
To record audio along with the EGG waveform, the supplied high-quality electret capacitance microphone
is plugged into the XLR jack on the rear panel, or a user-supplied microphone can be plugged into the 1/8”
phone jack on the front panel.
Before using the EG2-PCX electroglottograph, the (internal) dual batteries should be initially charged for
roughly 2 to 6 hours, 2 hours if the battery-condition light (near the Power switch) shows green with the
power switch ON, both to the right and to the left, and 6 hours if either of the On positions results in an
amber or red ‘low battery’ signal.
To charge the batteries, plug the charger into the receptacle found on the back of the electroglottograph.
Place the battery selector switch in the center "OFF" position. In this position both batteries will be charged
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simultaneously. A more complete explanation of the battery selector functions can be found later in this
manual.
FOR MAXIMUM BATTERY LIFE, DISCONNECT THE CHARGER WHEN THE UNIT IS
STORED FOR LONG PERIODS.
Totally discharged batteries are usable after about two hour’s charge and reach full charge
when charged overnight.
The battery charger is specifically designed to match the charging requirements of the
EG2 and EG2-PC batteries. Do not use any other type of charger unit.
The batteries are standard 6 Volt lead-acid gel cells and are field replaceable by a qualified electronics
technician, after removing the top cover.
ELECTRODE INSTALLATION AND POSITIONING
1)
Insert the modular plug of the EL-2 electrode cable into the receptacle marked "ELECTRODES".
2)
Cover the gold surfaces of the electrodes with a very thin coating of water-soluble electrode gel. (A
salt-water solution can also be used to wet the electrodes if no gel is available.)
3)
Place the electrodes onto the neck so that they are approximately at the level of the thyroid cartilage
and about 3/16 inch (0.5 cm) apart at the front of the neck. The left electrode (from the patient's
perspective) typically has red wires going to it. If no color indicator is visible, refer to the picture
below for proper orientation of the electrodes before placement on the patient. If placed properly on
the neck, the narrow gap separating the gold-plated areas on each electrode should be
approximately horizontal (parallel to the Velcro band), and not vertical or diagonal.
4)
While having the subject produce a constant, prolonged vowel sound in the pitch range to be tested,
adjust the vertical position of the electrodes such that the "Electrode Placement/Laryngeal
Movement" indicator is centered on the green LEDs. This should place the electrodes in an optimal
position so that small vertical movements of the larynx will have minimal effects on the accuracy of
the EGG waveform. (The EGG unit output need not be connected to perform this check.)
5)
Once the electrodes have been optimally positioned, the subject can hold the electrodes in place
using the thumb and index finger, or by using the strap provided. Either way, be sure that the
electrodes are completely in contact with the skin at all times.
6)
Connect the output of the EG2-PCX to the recording/display system it is to be used with, if not
already connected.
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Electrode Cable
Glottal Enterprises electroglottographs are normally supplied with 34mm diameter two-channel electrodes.
However, smaller 27mm electrodes may be supplied as an option. Electrodes are backed with Velcro for
use with the neck strap. We recommend holding the electrodes firmly in place with the thumb and index
finger if this is practical.
We also recommend that the electrodes be cleaned with water between sessions and that the metallic
(gold plated) surfaces be covered with a very thin coat of water-soluble electrode gel before each use, or
wet with a salt-water solution. (The gel or salt water may not seem necessary in damp weather or with
some subjects, but we have found poor waveforms to occasionally result with dry electrodes.) For best
channel separation, the insulating strip between the metallic surfaces on each two-channel electrode
should be kept relatively free of gel. However this is not critical for acceptable performance.
DESCRIPTION OF CONTROLS and CONNECTORS
FRONT PANEL
(1) Battery Switch and Power Indicating Light
This 3-position rotary switch selects which battery the unit is powered from. With the battery charger
plugged into the rear of the unit and the battery switch in the "A" position, battery "A" is being used to
power the EGG while battery "B" is being charged. The reverse is true with the switch in the "B"
position. With the BATTERY switch in the "OFF" position, the EGG is off, and both batteries will be
charged simultaneously. When the unit is on and the battery being used is charged sufficiently, a
green power indicating light is seen near the BATTERY switch. The light will change color to amber as
the voltage of the supply battery diminishes, alerting the operator to switch to the other battery.
Note: In some cases, the EGG output can degrade slightly with the power light still showing green (just
before the amber low-battery light is triggered). If there is any reason to suspect that this is the case,
switch to the fully charged battery and look for a change in performance. (This easy way to verify battery
performance is one advantage of the dual-battery system.)
Note: The EGG unit can normally be used with the battery charger connected. However it is conceivable
that with some power line sources interference may occur that degrades EGG performance. If you suspect
that this may be the case, try disconnecting the charger. (If you have a verified instance of such interference
occurring, Glottal Enterprises would appreciate hearing about it so that we may alert other users.)
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(2) ELECTRODES jack
The ELECTRODES jack accepts the modular plug of the electrode cable. The plug and receptacle
become firmly interlocked and can only be disconnected by pressing the release tab on the plug.
(3) Electrode Placement/ Laryngeal Movement indicator
This indicator displays a signal which value varies with the relative distance between the level of the
glottis and the midpoint between the upper and lower electrode pairs. For routine clinical use we
recommend an electrode placement such that the tracking display is green. With this electrode
placement slight vertical movements of the larynx or electrodes will have a minimal effect on the
performance of each channel, and each channel output will be only slightly weaker in amplitude than
its maximum possible value.
(4) OUTPUT GAIN switches
The EG2-PCX is supplied with a 2-position switched gain control for both EGG and audio signals. In
the High position this switch increases the amplitude of the EGG output signal by a factor of eight, and
the microphone output by a factor of four (12 dB). For the EGG signal, the High gain should normally
be used only when a speaker's neck physiology results in a signal with a reading below the green LED
on the SIGNAL STRENGTH indicator with the switch in the LOW position.
Note: An advantage of the switched gain over a continuous gain control is that it allows the user to
compare signal levels from various users and ascertain if the signal level is sufficient for a reliable
EGG signal. EGG sensitivity in either switch position can be verified by using the LS-1 Larynx
Simulator available from Glottal Enterprises.
(5) EGG SIGNAL STRENGTH indicator
The SIGNAL STRENGTH indicator monitors the relative amplitude of the EGG output (the sum of the
two EGG channels). Though precise thresholds for signal strength required for proper operation have
not yet been determined, a scale reading in the amber area of the indicator with the output gain switch
in the High (most sensitive) position may indicate that the output signal is too weak to be relied upon
as an accurate indication of the variation of the vocal fold contact area. (A considerably weaker signal
may be adequate for applications such as F0 measurements, in which the details of the waveform are
not important.)
(6) MICROPHONE INPUT jack – front panel
The 1/8 inch phone jack on the front panel accepts any dynamic microphone or self-powered electret
capacitor microphone. If a microphone is plugged in here, the XLR microphone jack on the rear panel
is deactivated.
REAR PANEL
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(7) MICROPHONE INPUT jack – rear panel
This XLR-style jack can accept any microphone having a XLR connector, however, it is specifically
designed to accept the ECM8000 omnidirectional electret microphone supplied with the EG2-PCX.
It will supply the excitation voltage required by the microphone.
Note: The ECM 8000 microphone should be held vertically, with the tip about a centimeter from the
corner of the mouth. This location will yield a high fidelity signal that can be used either for inverse
filtering or spectral analysis. The user is referred to the Glottal Enterprises WaveviewStudent CD for
examples of voice analysis by inverse filtering using the EG2 electroglottograph and ECM 8000
microphone. There are a number of spectral analysis programs that permit a comparison with a
simultaneous EGG signal, as the software sold by VoceVista.
(8) Data Output USB jack
The Data Output jack connects to a computer having a USB input jack, and transmits the EGG and
microphone signals in digital WAV–file format, sampled at 44 kHz. The jack supplies power from the
computer to the EG2-PCX’s internal A-D system, however, the power to the EGG circuitry and audio
preamplifier still comes from the unit’s internal rechargeable batteries.
(9) SIGNAL OUTPUT Jack
This rear panel stereo 1/8” phone jack supplies in analog form the EGG and microphone signals sent
to the internal A-D converter. The signals from this jack can then be monitored on an oscilloscope or
sent to an external data acquisition system (for example, if more than two channels of data are to be
recorded). The tip of the stereo connecter presents the microphone signal and the ring the EGG signal.
(10) PLAYBACK audio jack
This jack connects to the audio output of the EGG2-PCX internal A-D system. It can be used with
headphones or an external audio system for auditory monitoring of a recorded signal. (On many
computers, the computer’s internal audio card can also be used for this purpose. However connecting
the EG2-PCX via the USB jack will normally disable both the record and playback functions of the
computer’s audio system, and the playback functionality would have to be re-enabled. See your
computer’s manual to accomplish this.)
(11) Charger input jack and charging indicator light,
Accepts the supplied Glottal Enterprises battery charger. Use only the supplied charger.
Optional rear panel outputs - Other optional outputs, if so equipped, are located on the back
panel and may include the following. All will be BNC-type jacks unless specified otherwise.
:
F0 TRIGGER Output
This signal can be used to reliably measure vocal fold fundamental frequency. The jack provides a 0.1
msec positive-going pulse or spike for each glottal cycle, synchronized to the glottal closing phase. The
time between pulses is the vocal period T0, and the vocal fold fundamental frequency can be computed as
F0 = 1/ T0. Since it provides a signal of uniform spectrum that follows the F0 contour of the speech, the
signal at this output is also useful as an input to acoustic voice analyzers that permit pitch-synchronous
voice analysis, to certain speech synthesizers, or as a phase-settable trigger for laryngeal stroboscopy.
LARYNGEAL TRACKING Output
This output provides the user with the ability to record the DC voltage that is applied to the LARYNGEAL
TRACKING INDICATOR. If recorded on a third channel of an external data acquisition system, this signal
can be used for verifying proper electrode placement or for tracking vertical movements of the larynx
during speech or singing.
CHANNEL A and CHANNEL B Outputs
These outputs provide the user with the separate Channel A and Channel B signals of the dual-channel
EGG.
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EG2-PCX SPECIFICATIONS
Electrode Size:
34mm Diameter, Gold Plated (Normal)
27mm Diameter, Gold Plated (Optional)
Interelectrode Voltage:
1 volt rms typical, 1.5v Max
Carrier Frequency:
2MHz
EGG Internal Noise:
Equivalent to a change in interelectrode impedance of 0.001% or less, at an
average electrical neck impedance of 150 Ohms.
Frequency Response:
20 Hz to 6 kHz, -3dB.
EGG Sensitivity:
With the Gain Switch in the High position, the EGG change in the output signal
is approximately 2.2 volts for a change of interelectrode impedance of 0.1 %.
In the Low position the output change would be reduced by a factor of eight to
approximately 0.28 volts.
Limited Warranty
Glottal Enterprises, Inc. warrants, subject to the conditions and restrictions contained below, that each
product and device manufactured and sold by Glottal Enterprises, Inc. shall be free from defects in
materials and workmanship for a period of one (1) year from the date of purchase from Glottal
Enterprises, Inc.
Should a product manufactured by Glottal Enterprises, Inc. fail to conform to this written warranty, Glottal
Enterprises, Inc. will, at its option, either repair or replace the product at no cost to the purchaser or, at
Glottal Enterprises, Inc. option, refund the purchase price of the product.
The following shall not be considered defects in materials or workmanship:
Damage caused to the product by others or by any cause beyond the control of Glottal Enterprises, Inc.,
including but not limited to damage caused by misuse, abuse, mishandling, or by fire, flood, earthquake,
storm, or other acts of nature.
Claims under this Limited Warranty must be made in writing to Glottal Enterprises, Inc. within one year from
the time of purchase. Claims should detail the nature of the problem and the name, address and telephone
number of the person making the warranty claim. Glottal Enterprises, Inc. reserves the right and must be
given at least thirty (30) days to examine the claimed defective product and to act on the warranty claim.
This limited warranty extends only to the original purchaser of the Glottal Enterprises, Inc. product
and in any event no compensation under this warranty shall exceed the original invoice price at the
time of purchase from Glottal Enterprises, Inc.
This aforesaid obligation of Glottal Enterprises, Inc., to repair or replace defective products, or at Glottal
Enterprises, Inc. option, to refund the purchase price, shall be the limit of Glottal Enterprises, Inc. liability.
There is no implied warranty of merchantability. There is no warranties expressed or implied which extend
beyond the conditions and remedies described herein.
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