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Purpose: This study examined whether the intraoral transducers used in electromagnetic articulography (EMA) interfere with speech and whether there is an added risk of interference when EMA systems are used to study individuals with aphasia and apraxia.
Method: Ten adult talkers (5 individuals with aphasia/apraxia, 5 controls) produced 12 American English vowels in /hVd/ words, the fricative-vowel (FV) words (/si/, /su/, /∫i/, /∫u/), and the sentence She had your dark suit in greasy wash water all year, in EMA sensors-on and sensors-off conditions. Segmental durations, vowel formant frequencies, and fricative spectral moments were measured to address possible acoustic effects of sensor placement. A perceptual experiment examined whether FV words produced in the sensors-on condition were less identifiable than those produced in the sensors-off condition.
Results: EMA sensors caused no consistent acoustic effects across all talkers, although significant within-subject effects were noted for a small subset of the talkers. The perceptual results revealed some instances of sensor-related intelligibility loss for FV words produced by individuals with aphasia and apraxia.
Conclusions: The findings support previous suggestions that acoustic screening procedures be used to protect articulatory experiments from those individuals who may show consistent effects of having devices placed on intraoral structures. The findings further suggest that studies of fricatives produced by individuals with aphasia and apraxia may require additional safeguards to ensure that results are not adversely affected by intraoral sensor interference.
KEY WORDS: speech production, electromagnetic articulography, fricative spectral moments, aphasia, apraxia of speech
Speech production is studied using techniques that provide anatomical images or movies of articulation (e.g., cineradiography, videoflouroscopy) as well as techniques that derive individual fleshpoint data during speech movement (e.g., X-ray microbeam, selspot, and electromagnetic articulography [EMA]). A potential complication of fleshpoint tracking systems is that the sensors used to record speech movement may themselves alter participants' speech. For instance, intraoral sensors might obstruct the speech airway, resulting in sound patterns not normally observed in speech. It is also possible that data recorded during EMA or X-ray microbeam studies may to some extent reflect participants' compensation for the presence of intraoral sensors in the vocal tract. Indirect evidence concerning these issues was provided by Perkell and Nelson (1985), who compared formant frequencies of the vowels /i/ and /u/ recorded in the...