Research
Funded Projects
Cross linguistic studies on spoken language processing. NIH Grant # R01 DC 04421
Keith Johnson, Molly Babel, Grant McGuire, & Reiko Kataoka
The long-term objective of this research project is to understand human spoken language processing (particularly speech perception and auditory word recognition) in linguistic context. Speech signals are unique in human experience because they are highly familiar, and have great practical significance in daily life. Therefore, it is not too surprising to find that people develop optimized processing strategies tuned specifically for speech. In this work we study how this tuning process may be sensitive to linguistic structure. Cross-linguistic spoken language research is important because without it we are in danger of concluding that the phenomena found in one language (or even dialect) are somehow normative for speakers of other languages. Such a narrow understanding of 'normal' spoken language processing is likely to have a negative impact on clinical speech and hearing practice in a pluralistic society.
Studies of the inner structure of distinctive features. NSF grant BC9817243
John Ohala & Keith Johnson
In this project we propose to investigate temporal and spectral aspects of the cues underlying speech features, the perceptual consequences of these properties, and the link between these and common cross-language sound patterns. Specifically, we study (1) the relationship between given cues' duration, their perceptual saliency, and their utilization in languages' segment inventories, (2) the perceptual basis of dissimilation, (3) the phonetic origins of vowel harmony, (4) and asymmetries of consonant confusions. In addition to leading to a greater understanding of the physical structure of speech and providing a phonetic base to phonological theory, these results have potential applications in speech technology as well as in clinical phonetics and in language teaching.
Ongoing work
Speech Aerodynamics
John Ohala, Keith Johnson, & Ronald Sprouse
We are studying patterns of nasal coarticulation and phonation types using recordings of nasal and oral airflow and pressure. We have recently (2007) up-graded our equipment thanks to a grant from the Holbrook Experimental Phonetics Fund. Tilsen and McGuire plan to use the equipment to study the phonetic basis of syntactic patterns.
Exemplar models of phonology
Keith Johnson, Marc Ettlinger
Ettlinger is extending Johnson's earlier work on exemplar-based speech perception with models of phonological change using exemplar-based language learning agents. The aim of this project is to test through model simulations the degreee to which patterns of phonological change can be attributed to simple "first principles" of spoken language perception and production.
Corpus Phonetics
Keith Johnson, Yao Yao
Yao is using methods of spectral template scoring that Johnson developed in connection with an automatic speech recognition project. The aim of this project is to develop methodologies that make it possible to extract robust acoustic phonetic measurements from tagged speech corpora. Yao's first foray into this domain was to develop a stop release burst detection algorithm which finds the burst to within 5ms. Interestingly, bursts are often (xx%) missing in voiceless stops in conversational speech.
Visual Phonetics
Keith Johnson, Christian DiCanio
The aim of this project is to test the hypothesis that the phonetic basis of sound change is visual as well as acoustic. We are looking at how place of articulation in nasal coda consonants may be sensitive to visual phonetic and acoustic phonetic properties of nasal consonants.