Biomedical subjects

Khalil Iskarous

Publications and source records attributed to Khalil Iskarous.

4 recordsLinked to original sources

PubMed2005

The Haskins optically corrected ultrasound system (HOCUS).

The tongue is critical in the production of speech, yet its nature has made it difficult to measure. Not only does its ability to attain complex shapes make it difficult to track, it is also largely hidden from view during speech. The present article describes a new combination of optical tracking and ultrasound imaging that allows for a noninvasive, real-time view of most of the tongue surface during running speech. The optical system (Optotrak) tracks the location of external structures in 3-dimensional space using infrared emitting diodes (IREDs). By tracking 3 or more IREDs on the head and a similar number on an ultrasound transceiver, the transduced image of the tongue can be corrected for the motion of both the head and the transceiver and thus be represented relative to the hard structures of the vocal tract. If structural magnetic resonance images of the speaker are available, they may allow the estimation of the location of the rear pharyngeal wall as well. This new technique is contrasted with other currently available options for imaging the tongue. It promises to provide high-quality, relatively low-cost imaging of most of the tongue surface during fairly unconstrained speech.

Humans↗

PubMed2004

Vowel production and perception: hyperarticulation without a hyperspace effect.

The ability of speakers to exaggerate speech sounds ("hyperarticulation") has led to the theory that the targets themselves must be hyperspace hyperarticulated. Johnson, Flemming, and Wright (1993) found that perceptual "best exemplar" choices for vowels were more speech extreme than listeners' own productions. Our first experiment, using their procedure, only partially replicated their results. Low vowels vowel perception showed a higher F1, consistent with hyperspace. Front vowels also showed more frontness in F2, but back vowels were less extreme ("hypoarticulated") on F2. Our second experiment used an identification and rating of each stimulus, yielding similar results of a smaller magnitude. Our results indicate that the perceptual space is calibrated to a particular (synthetic) vowel space, which is not related straightforwardly to the speakers' spaces. The original hyperspace hypothesis can be attributed to the methodology which led to extreme judgments and of the fronting of back vowels in California English. The present results indicate that no such hypothesis is needed. Vowel targets are measurable from an individual's productions, and the individual's perception of other speakers (even synthetic ones) is based on information about the vocal tract and dialect of the speaker.

Adult↗

PubMedDate not supplied

Functional segments in tongue movement.

The tongue is a deformable object, and moves by compressing or expanding local functional segments. For any single phoneme, these functional tongue segments may move in similar or opposite directions, and may reach target maximum synchronously or not. This paper will discuss the independence of five proposed segments in the production of speech. Three studies used ultrasound and tagged Cine-MRI to explore the independence of the tongue segments. High correlations between tongue segments would suggest passive biomechanical constraints and low correlations would suggest active independent control. Both physiological and higher level linguistic constraints were seen in the correlation patterns. Physiological constraints were supported by high correlations between adjacent segments (positive) and distant segments (negative). Linguistic constraints were supported by segmental correlations that changed with the phonemic content of the task.

Adult↗

PubMedDate not supplied

Detecting the edge of the tongue: a tutorial.

The goal of this paper is to provide a tutorial introduction to the topic of edge detection of the tongue from ultrasound scans for researchers in speech science and phonetics. The method introduced here is Active Contours (also called snakes), a method for searching for an edge, assuming that it is a smooth curve in the image data. The advantage of this approach is that it is robust to the noisy speckle that clouds edges. This method has been implemented in several software packages currently used for detecting the edge of the tongue in ultrasound images. The tutorial concludes with an overview of the scale-space and Kalman filter approaches, state-of-the-art developments in image processing that will likely influence work on tongue edge detection in the coming years.

Humans↗