Perceptual and Acoustic Research
IAC Sound Booth
Our 10′ x 10′ IAC sound attenuated booth is located in 400 Lorch Hall. The booth is large enough to support four concurrent participants in a perception experiment and features a custom pass-thru port to allow simultaneous ultrasound imaging and high quality audio recordings. The booth is generally configured for quick audio recording so a researcher can display prompts or a word list on the consultant’s digital display while isolating the recording/controlling computer from the microphone.
If you are a first-time user of the lab please see our video: recording audio in the sound lab.
Perceptual testing is a primary focus of our laboratory. Our facilities include four macbook computers; four Cedrus response boxes; low latency keyboards; SuperLab, e-Prime, and Linger software; and an array of small but necessary devices: AKG circumaural headphones, edirol USB audio interfaces, mixing boards, pre-amps, etc.
We are fortunate to have a fruitful partnership with Julie Boland’s Psycholinguistics Lab. We work closely with her on projects using the SR Research Eyelink ii eye tracker. A pair of high-speed (500Hz) cameras are focused on a participant’s pupils and calibrated so the velocity and acceleration of eye movements can be used to determine saccades and fixations to pre-determined areas of interest on a computer screen. We use the excellent temporal resolution of this online behavioral task to test hypotheses about the time course of speech perception (e.g. coarticulation or the influence of non-speech factors in perception).
We have recently acquired a Zonare scan engine ultrasound device for performing research and data collection on the surface of the tongue. The ultrasound unit can be docked (as shown) on the cart, or removed for in-class demonstrations.
The unit can also be connected to a computer using a frame grabber device (an Epiphan DVI2USB) for direct and automated data collection. The device is sufficiently portable and compact to be taken into the field for articulatory research.
The SQLab EVA2 pneumotachograph measures oral and nasal airflow by measuring air pressure differences during continuous speech. Oral airflow is captured by a pliant silicone mask that forms a seal around the mouth. Nasal airflow is captured by tube(s) placed at the entrance of the speaker’s nostrils.
In this system, air passes through a mesh screen, and pressure transducers measure the pressure drop across the screen. Because airflow equals pressure divided by the impedance of the pathway, and the impedance of the mesh screen is known, airflow can be calculated directly. Intra-oral and sub-glottal air pressure can also be measured through the creative use of catheters.
Airflow and high-quality audio are captured simultaneously, and are automatically synchronized by specialized software (running on a dedicated PC workstation) that also applies a smoothing algorithm to the airflow traces.
The Glottal Enterprises EG2-PCX electroglottograph is a non-invasive tool for measuring vocal fold vibration. A speaker wears a neck strap holding a pair of electrodes in place around the glottis (LED indicators on the EGG allow for precise location of the electrodes). The system then sends a low-voltage, high frequency current between the electrodes (two separate currents between the upper and lower halves of each electrode) and reads changes in electrical impedance across the vocal folds as opening (high impedance) and closing (low impedance). The result is a wav file that can be read in any standard software. Please see our video: configuring the EGG and collecting time-aligned EGG and audio signals with Audacity
With the EGG and a microphone you can also amaze and impress your friends and family by measuring precisely how far the microphone was from the speaker’s vocal folds at the time of recording.