The UCLA Phonetics Lab has equipment that enables one to record the airflow from the mouth and nose. In addition, it can record the pressure of the air in the front of the mouth and in the pharynx. The system is illustrated in Figure 1. It consists of a small box (bottom left of the picture) connected to a laptop or desktop computer (bottom right), and an assembly with oral and nasal masks and pressure tubes held by the speaker, together with a microphone that records the sound.
Figure 1. The system for recording air pressure and air flow described in the text
The mask for capturing the oral airflow fits around the mouth and below the jaw. The nasal airflow mask is fastened over the nose by a band that goes around the head. Both masks are joined to the assembly by small tubes.
Some notes on connecting the assembly:
Recording the airflow:
Tips for recording :
Figure 2 has three records made of"He paid the price ", with the emphasis on the second word.
Figure 2. Audio, oral flow and pressure records during the sentence "He paid the price".
The scales, like those in figure 2,allow us to measure the airflow and pressure data so that we can quantify the differences between sentences.
Flow is measured in terms of the volume of air that passes a given point in a second. (We normally speak of the airflow through the lips or the nose, although we are really measuring the volume of air that passes across the mesh in the mask). The units are milliliters per second (ml/s). Calibrating the rate of flow requires the apparatus shown in figure 3. A fan produces a steady airstream that flows through the mask and then on through a special flow calibration tube containing a ball that is blown higher in the tube as the flow is increased.
Figure 3. A system for calibrating airflow.
Pressure is measured in
terms of the force required to raise or lower the height of a column of
water by a certain amount. This corresponds to how much effort you would
have to use to blow bubbles out of a tube immersed in water as shown in
figure 4. This technique can be used to calibrate a pressure measurement
system as shown in the figure.The figure shows a force being exerted to
produce bubbles at the end of a tube 12.5 cm below the surface, a pressure
of 12.5 cm H2O.
Figure 4. A simple system for measuring pressure.
Calibration measurements can be made more accurately by using a U-tube as shown in figure 5. When the tap is open, the tube can be filled with water to the zero level, with the water level reaching the same height in both branches. The figure shows what happens when the tap is closed and pressure is applied by pushing the syringe down. In this case the level has gone up by 5 cm on the one side and gone down by 5 cm on the other side, so that the pressure being applied is 10 cm H2O.
Figure 5. Using a U-tube to calibrate pressure.
Here in the UCLA phonetics lab, we have facilities for acquiring aerodynamic data with. The lab is equipped with Rothenberg masks and small tubes for attaching the masks to the assembly. These masks can be used with either Macquirer or either of the 4-channel CSL boxes.All of the equipment for aerodynamics is located in the General Lab.
About this page
The information on this page has been adapted from the forthcoming Analyzing phonetic data: An introduction to fieldwork andinstrumental phonetics by Peter Ladefoged.
This page was created by Rebecca Brown and Christina Esposito.