The Glottal Enterprises EG2-PC is an electroglottograph, a device for measuring vocal fold and larynx activity. It measures vocal fold contact area (VFCA) and larynx movement. VCFA can be treated as if it were an audio signal, but both signals are within the range accepted by the Macquirer 516, which will be used as an interface between the EG2-PC and the Macquirer software.
!! 2 Startup
To turn on the EG2-PC, turn knob on the front of the box to A or B, making sure that a green LED above the knob lights up when you do.\\
!! 3 Cleaning and sanitizing
Before and after each session with the EGG, clean the electrodes the same way as the masks. It is important to wipe off all of the gel before sanitizing with alcohol, and then to let the electrodes air dry.\\
!! 4 Connections
Plug the electrodes into the ethernet-style (RJ-45) jack in the front of the EG2-PC, as in Figure 2.
One black and one white cable should be attached to the back of the EG2-PC.
The black cable should be connected to the 1/8" phono output, and the white cable should be connected to the larynx tracking BNC output.
The black cable is made specifically for connecting the EG2-PC to the Macquirer 516 or the microphone input of another device.
While it is possible to plug either end of the black cable into the EG2-PC output, the EGG signal will only be received if the "stereo" end with three conductors is connected to the EG2-PC and the "mono" end with two conductors is connected to the other device.
If you are measuring vocal fold contact area, connect the black cable to the CH2 input on the front of the Macquirer 516.
If you are measuring larynx movement, connect the white cable to CH4.
If you are not measuring larynx movement, then you do not need to use MacQuirer.
You can treat the vocal fold contact area signal as audio and use Praat to record and display it.
Table 1 summarizes which data sources are assigned to which channels with and without the EGG connections.
See the Aerodynamics section for more instructions for using the EGG together with the MacQuirer hardware.
!! 5 Preparing to collect data
If you are collecting EGG data, coat the electrodes with a thin layer of gel, place them against either side of the speaker's larynx (with wires pointing down) and secure it behind the neck with the velcro straps, as in Figure 6.
Figure 6: Proper placement of the EGG electrodes
With the EGG box powered on, watch the green, yellow, and red LEDs labeled ELECTRODE PLACEMENT, which will tell you whether the electrodes are too high or too low against the speaker's larynx, and adjust the electrodes until one of the green LEDs in the middle is lit when the subject is at rest.
When the speaker produces a voiced sound, the LEDs labeled SIGNAL STRENGTH should light up, showing the signal strength, and the ELECTRODE PLACEMENT LEDs, which double as LARYNGEAL MOVEMENT LEDs, should reflect laryngeal movement.
The EG2-PC has toggle switches to control output level. These should normally be set to LOW, but if you are having trouble getting a strong enough signal, you can try switching to HIGH.
Without using MacQuirer/PCQuirer, it is also possible to capture the EGG output directly with the "line-in" jack on newer Mac and PC with sound cards. In fact, using the coaxial cable with one end connected to the four outputs in the back panel, it is possible to collect four different types of EGG signal. However, the most useful one is probably the "PC" output jack in the back that sends VFCA.
If you need to do simultaneous audio / EGG recordings, several options exist:
1. Use newer versions of PCQuirer/MacQuirer. The interface is easy to use, but you can't do it on your own laptop unless you have the license.
2. Use the microphone jack in the front panel for audio input, and capture EGG/speech as two separate channels of a stereo signal from the PC output jack. This gives your flexibility in where to record, but it takes some work to set this up. Below is the instructions:
Step 1: Make sure both ends of the black cable connecting the PC output jack and the "line-in" jack on your computer have three conductors. (If you followed the instruction above, you will need to replace the cable!) This is necessary for sending a stereo signal.
Step 2: The trickiest part is to choose a microphone or a preampt that matches the impedance of EG2-PC's microphone input. Check your mic's specifications to find out the impedance value (in ohm). If it is in the low 100 or 200's it's considered a low impedance mic. It will not work work with EG2-PC because of the impedance mismatch. If you try you will get a lot of noise. If you are not sure, a good rule of thumb is to check the connector of the mic. If it's a 1/4'' or 1/8'', then it's probably high-impedance. If it's an XLR connector (the big one with three pins), then most likely it's a low-impedance mic. Note: simply using the XLR-TRS adapter would not affect the impedance, and increasing the gain in preampt will also increase the noise level. Matching impedance is the way to go. In addition, the 1/8" jack in the front panel does not send any voltage and only works with dynamic microphones or condenser mics that already has power.
Step 3: Calibration. If the impedance match is not perfect between EG2-PC and the mic, some power loss will occur and you will only see a very weak signal in the speech channel. When this happens, you can set the output level of "mic" to "high", and use the adjust gains in your computer sound card to avoid clipping. This is not perfect, since you cannot adjust the gain of the mic, but unless you find a preamp that has an output impedance matching EG2-PC's, this can result in an acceptable sound pressure level.
Step 4: Recording. Use a software that supports stereo recording, e.g. Praat. Then you can extract the left and right channels separately as two separate signal that are synchronized.