UCLA Phonetics Lab

ELECTROMAGNETIC
ARTICULOGRAPHY
(EMA)


The Phonetics Lab owns a Carstens system (AG100) for electromagnetic articulography (EMA). Currently we have 10 receiving pellets, which can be placed midsagitally inside the mouth or on the face to measure movements during speech production.

EXPERIMENTAL STEPS

STEP 0: Sterilization and Disinfection

Sterilize and disinfect materials (sensor coils and tweezers) by using 2 % glutaraldehyde (available as CidexPlus (Johnson & Johnson)). Immerse sensors and tweezers completely in the CidexPlus Solution for a minimum of 10 hours for STERILIZATION

Less than sterilization is possible, but not usually used here: immersion in glutaraldehyde for a minimum of 20 minutes for HIGH LEVEL DISINFECTION; immersion in ethyl alcohol (75 ~90%) for 20 minutes followed by wiping with Povidone-Iodine can be used for disinfection only (not for sterilization).   



STEP 1:  Warming-Up

The system must be turned on at least two hours before the actual experiment, in order to allow the coils to warm up and reach a stable temperature. Once the computer and the EMA system are on, it is necessary to start the Art program for the warm-up procedure to begin (after Art starts, you can exit the program and use the computer for other purposes). See the Carstens website and the UCLA homemade manual for details on Art.

STEP 2:  Coating Sensors

Dip the sensors into Plasty-Late (modelers plastic)  to coat them. This step protects the sensors by facilitating adhesive removal after the session and also helps keep them clean. (It is also fine to dip the wire about 1-3 inches into Plasty-Late). The solution is milky when wet but transparent when dry.
 

STEP 3: Attaching Silk Cloth

(Optional but Recommended) Attach the sensors to small circles or squares of silk cloth right after dipping them in the plastic coating (so the cloth sticks to the sensor). (See Figure (3) below.)  As can be seen in Figure (4),  the cloth expands the surface of the sensor coil that is attached to the tongue and consequently helps preventing the sensors from falling off. This step is only recommended for coils that will be attached to the tongue.


STEP 4: Drying the Plastic Coating

It is important to leave the plastic coating to dry for at least 2 hours (the longer the better - as a general rule, we leave the coating dry for one night), at which point the sensors can be calibrated in the magnetic field.  Insufficient drying may cause the coating to be broken more easily, which results in the sensors' falling off.

 

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STEP 5: Positioning the helmet

The helmet which generates the field is positioned around the subject's head. Since the helmet is rather heavy, it is suspended from a pulley, in order to alleviate some of the weight.
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STEP 6: Placing the sensors

A. Calibration Procedures

    It is essential to perform a calibration of the system before each experiment.
    Please go to our UCLA Homemade EMA Manual for detailed Calibration Procedures.

B. Materials for Attachment

In order to place the sensors, several materials should be prepared.
 

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    C. Attachment Procedures

    It is recommended that two experimenters conduct the attachment session.
     
    1. Hold the sensor coils (Reversal Tweezers) -- Experimenter 1.
    2. Thoroughly dry the area to which the sensor coil is to be attached with a cotton gauze pad. (Cotton Gauze Pad) -- Experimenter 2
    3. (Optional) Put a dot on the spot of the tongue to which the sensor coil is to be attached. (Cosmetic Pencil) -- Experimenter 1
    4. Apply a drop of the internal adhesive to the surface of the silk cloth (on  the sensor coil) (Cyano-Veneer) -- Experimenter 2
    5. Wipe out the surface of the tongue quickly (New Cotton Gauze Pad) -- Experimenter 1
    6. Place the coil -- Experimenter 1   [Steps 4-6 must be done almost simultaneously]
    7. Release the tweezers immediately. (It is important to release the tweezers immediately after the attachment in order to prevent the tweezers tips from sticking to the coil.) -- Experimenter 1
    8. Dry the surface around the coil using a hair-dryer for about two minutes -- Experimenter 2. Experimenter 2 must start drying the subject's tongue (using cold air) from the moment in which the coil is attached. This procedure helps the sensor coils to stick to the surface of the tongue longer.  (For a short data collection session, this step can be omitted.)
    9. While the tongue is being dried, press the top of the coil with the tip of the tweezers for at least 30  seconds, starting immediately after the coil is attached (remove the tweezers periodically, to make sure that they did not stick to the coil). Of course, during this and the previous step the subject's tongue should remain in a position in which the coil is accessible/visible. -- Experimenter 1
    10. Stabilize the fine lead wire with a strip of medical tape on the cheek. (These wires must be led out via the corner of the mouth and across the cheek).

 
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Processing the data [using Tailor]

Restoring 12 bit acoustic data [using Multi-CV]

Analyzing the data


 *An animation of the articulators in motion, created from EMA data, is also available on the Demos and Illustrations page.
 


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     Important Tips & Reminders

    1. Attach a small circle/square of silk cloth to the sensor coils right after dipping into "Plasty-late"
    2. Thoroughly dry the rubber coating (at least 3 hours) before the experiment starts
    3. Pay extremely careful attention to drying the surface of the tongue right before placing a sensor coil. Make sure that the surface is wiped twice. Drying the tongue is so important that other institutes use a "saliva vacuum" like the one dentists use.
    4. Gently press the sensor coil against the tongue surface with the tips of the tweezers or a finger for about 30 seconds.
    5. During the placement procedure, the second experimenter should dry the subject's tongue with a hair-dryer. This helps the glue drying thoroughly.  In other institutes, a tiny nozzled air blower like the ones used by dentists is used to blow air on the glued sensor coils.
    6. Reversal Tweezers makes the coil placement easier, preventing the sensor coils from slipping out.
    7. It's always a good idea to have two experimenters performing the coil placement. One experimenter holds the coil, quickly wipes the tongue, places the sensor coil, and gently presses the sensor coil against the tongue. The second experimenter wipes the tongue before the placement procedure starts, puts a drop of glue on the silk-surfaced coil, blows the hair-dryer (with cool air).
    8. While their tongue is being dried, subjects tend to drool. Thus, it is a good idea to provide them with tissues that they can use to dry the lower half of their face. Also, it is a good idea to keep a towel on the subject's lap during the whole attachment procedure, to protect the subject's clothes from glue spillings.
    9. When attaching the coils to the base of incisors, make sure that the front teeth do not have fillers or any synthetic material that might be destroyed by the glue.
    10. It is a good idea to design experiments so they can be stopped part way through and still have useful data, just in case sensors accidentally detach earlier than expected.
    11. Dip the used sensor coils into Uni-Solve at least for several hours so that we can reduce the damage while peeling off the rubber coating. We typically soak them for a day or two to minimize the damage.  It is also suggested (Tips and Tricks at Carstens) that the loss of receiver coils due to broken leads at the coil base can be reduced by occasionally dipping the stripped-down coils in Cyano-Veneer up as far as the sleeve of the coils.

    12.  
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Last updated: 02/18/00 (by Taehong Cho)