Aerodynamics Equipment

Collecting articulatory data with the Macquirer 516


!! 1 Introduction

->The Macquirer 516 is an interface that allows you to collect instrumental data with the Macquirer speech analysis software. The most obvious application is to use it to measure airflow and pressure with the nasal and oral masks, but in principle it can accept data from any source which utilizes a DC electrical current within the right range.
->The Macquirer software can be used to collect and analyze audio, EGG, and airflow data. You may also export data in WAV form to analyze using different software (e.g. Praat).

!! 2 Startup

# Turn on or log into the Mac (Sweet).
# To turn on the airflow main system (Maquirer 516), press the button on the back of the box, below the power cord.
#  Connect the airflow main system box to the Mac using the USB cord. The Macquirer software will not open unless it can detect this hardware.
# To start the Macquirer software, click on the “Macquirer” application icon, located in Macintosh HD/Applications/Macquirer.
**When Macquirer opens, Click on Record/Play in the Options menu. you should see five channels (Audio, Ch1, Ch2, Ch3, and Ch4). You get to decide how to use them, because there are six data sources you might be interested in assigning to these channels:
***oral airflow
***oral pressure
***nasal airflow
***vocal fold contact area
***larynx tracker

!! 3 Cleaning and sanitizing

->Before and after each session with the airflow masks, clean and sanitize every part of the masks that comes into contact with the subject's face and inside the masks (but not the mesh window that lets air escape). First clean off anything that is on the surface, and then sanitize by applying alcohol with a cotton ball. Let the equipment air dry, to give the alcohol time to work.
!! 4 Connections
->Figure 1 points out some of the places on the Macquirer 516 where you are most likely to plug things in.
**Figure 1: Where to connect things**
->If you will be listening back to audio recordings, make sure that headphones are connected to the "Phone" jack on the Macquirer 516.
->The box that is attached to the oral mask contains two airflow transducers (Channels 1 and 3) and two pressure transducers (Channels 2 and 4). When the transducers receive airflow or pressure, they produce an electrical current which is sent to the Macquirer box via the SCSI cable. There is also a condenser microphone element connected to the airflow mask. The audio signal it receives is also sent to the Macquirer box via the SCSI cable.
->Follow these steps if you will be measuring airflow and/or pressure:
# Make sure that the SCSI cable on the oral mask/transducer box is connected to the SCSI port on the front of the Macquirer 516 as in Figure 2. Make sure nothing is connected to DC Channel inputs CH1, CH2, CH3, CH4, or Mic or Line, unless you wish to override the airflow, pressure, or audio data with data from another source (see Subsection 4.2 for that).
# Make sure that all three plastic tubes are connected to the masks and transducers properly. The CH3 FLOW transducer should be connected to one of the outlets of the nasal mask.
# Make sure that the flexible clear plastic part of the oral mask is pushed all the way onto the base of the mask and that the side with the wider indentation and the seam (where the chin goes) is on the side marked  Ch#3 and Ch#4, and that the nasal mask outlet that does not have a tube attached is closed, as in Figure 3.
**Figure 2: The oral mask**
**Figure 4: The nasal mask**



!! 5 Units of measurement

->The purpose of the flow and pressure transducers is to convert the relevant property of the air into something that can be transmitted through a wire. The transducers generate a DC current whose voltage is manipulated to reflect flow rate or pressure. Macquirer receives a DC electrical current from each of the data sources it is attached to. Since it does not know how the transducers converted from physical parameters to voltage, or even what physical parameters they were measuring, Macquirer's default is to display each channel's voltage in millivolts (mv). This directly expresses what the transducers are doing on the other end, but voltage is not the most meaningful way to discuss airflow and pressure.
->In order to display the commonly used units of airflow (milliliters per second) and pressure (millimeters of H20), Macquirer needs to be told how to convert millivolts back into these units. Thanks to Macquirer's calibration devices, we happen to know the functions. For a given voltage v (in millivolts), the formulas for converting back to airflow and pressure are:
-->CH1: oralairflow(ml=s) = 0.2865v'^2^' +  1.5736v + 14.852 
-->CH2: oralpressure(mmH2O) = 
-->CH3: nasalairflow(ml=s) =  0.7756v'^2^' + 13.768v + 88.351
->These formulas represent properties of the equipment, not the speaker. Pressure measured on channel 4 would be treated identically to channel 2, but airflow is different, because the oral and nasal masks offer different amounts of resistance to airflow (the same amount of airflow will produce a higher voltage via the nasal airflow mask and transducer, because the nasal airflow mask is not as leaky as the oral airflow mask. The functions are not linear, because the way the masks respond to airflow (how much air it leaks, etc.) depends on the rate of airflow. The pressure function is linear, so the coe±cient of v2 is zero. The only reason these formulas would change is if the equipment changes.
->The Macquirer software saves the calibration data from session to session, but you should check that they are correct before collecting data. After you've made a practice recording (see Section 7), select Calibration from the Options menu. The A, B, and C, and D columns are for the coefficients of the formulas given above. The Unit column is for you to name the units you are converting to with these formulas. Macquirer does not interpret the Unit names in any way. These are just labels that will appear on the screen for each channel. If you are measuring oral airflow, oral pressure, and nasal airflow, you will change the values in "ch 1", "ch 2", and "ch 3", to match Table 2. Any channel that is not used can be left at the default (0, 0, 1, 0). At this time, any channel which is receiving data from the EGG can also be left at the default, and quantified using arbitrary units (mv).
||! Signal Name ||! A   ||! B         ||! C          ||! D         ||! Units ||
|| ch1                || 0.0 || 0.2865 || 1.5736 || 14.852 || ml/s   ||
|| ch 3               || 0.0 || 0.7756 || 13.768 || 88.251 || ml/s   ||
->Table 2: Calibration information for three airflow/pressure channels
-->NOTE: As of April 5, calibration values in columns A and B revert to zero on saving. To avoid this problem, use the (less exact) linear calibration coefficients. The value in under C should be 9.8811 for ch 1 and  41.521 for ch 2.


!! 6 Preparing to collect data

**Figure 5: Proper placement of the oral and nasal masks**
-> Follow these steps to collect airflow and pressure data:
# If you are collecting nasal airflow data, have your speaker wear the nasal airflow mask by placing it on her nose and securing it behind her head with the velcro. The idea is that the masks are on tight enough to get a reasonably good seal, and loose enough to be reasonably comfortable.
# If you are collecting oral airflow or pressure data, have your speaker hold the oral airflow mask up to her face. If you are using both masks, the oral mask should fit underneath the nasal airflow mask, as in Figure 5.
# If you are measuring oral pressure, the small oral pressure tube inside the oral airflow mask should go between the lips. To measure pressure behind a lingual constriction, attach a piece of flexible tubing long enough to reach to the point in the subjects mouth where you wish to measure pressure. It may help to insert a paper clip into the tube so that you can manipulate the shape.
# If you are not measuring oral pressure, you probably should tape something soft like a cotton ball to the end of the oral pressure tube, so that it does not scratch the subject. When not in use, the tube should rest against the subject's chin.

!! 7 Collecting data

# Macquirer requires you to decide in advance how long you want to record. Decide how much time you want, and then from the Options menu, select Record/Play. . . and enter the number of seconds. Keep in mind that you will not be able to stop recording early. If you wish to record audio data using the mask, be sure that Input Source is specified as "Mic" in this menu.
# From the Record/Play menu, select Record (or just press Command-R).
# Ask your speaker to produce a practice utterance as naturally as possible (or in whatever style the actual data will be elicited).
# When finished recording, you should see an audio waveform and data for each of the channels you are recording data on, as in Figure 7. Each channel has a gain control in the Options -> Record & Play menu. You will probably need to adjust the gain on each channel to suit your speaker. You want a strong signal on each channel that isn't so strong that it gets clipped. When clipping occurs, you will see flat areas at the high or low end of the range, where the signal looks like it hit a wall and couldn't go any farther (which is what happened), as in 8. You also want to look out for levels that are too low, as in 9, because these recordings will not contain very much information. 
# Make more practice recordings until you are satisfied that your gains settings are correct. You will need to open a new window (Command-N) to make a new recording. Make sure that your practice utterances include the most extreme segments for each channel. For example, if you will be recording implosives or ejectives, make sure they aren't going to exceed the range of the larynx height or oral pressure channels. Make sure that nasals won't exceed the range of the nasal airflow channel, and that plosives won't exceed the range of the oral airflow channel, and so on.
# Next, move the cursor to a part of the recording where there is no speech, and click there. Then from the Channels menu, select Set Reference All, so that zero will be counted as zero. This will not affect the values you entered for calibration.
->Fortunately, Macquirer knows how to take into account the gains setting, and the values (in ml/s or mm H2O) will still be correct, as long as you have the gain at the same setting as when you made the recording (so if you record something and then change the gain, the numbers will be wrong. If you change the gain and then record something, the new numbers will be right).
**Figure 7: Data on five channels (audio, oral airflow, vocal fold contact area, nasal airflow, and larynx height)**
**Figure 8: Clipping on the nasal airflow channel: the gain is set too high.**
**Figure 9: Levels too low on the nasal airflow channel: the gain is set too low.**


!! 8 Other configurations

->The configurations described above should cover most situations,  although often you may not want to use more than a couple of channels. In case you do want to record from a combination of data sources not not included in one of the two configurations described already (e.g., if you want to record oral pressure and both types of EGG output), then you will want to assign the EGG output to channels other than CH2. If you run out of channels, it is also possible to record the standard EGG output (VFCA) on the audio channel, by plugging it into the MIC jack on the Macquirer 516. You will probably need to reduce the gain, and it may not be possible to reduce it enough to prevent clipping. When recording EGG data in the audio channel, you may want to record microphone audio to a different device (using an external microphone, since the mask microphone output is nullified by whatever is plugged into the MIC jack, such as a DAT recorder or another computer). The VCFA and audio signals are similar enough to allow time alignment later.


!! 9 Data analysis

->Data can be recorded by opening a log file in Macquirer and recording data at specific points in time or over intervals. Addition