Laryngeal Diadochokinesis (LDDK)
Laryngeal diadochokinesis (LDDK) is a quick and simple test thought to provide insight related to neuromotor function of the larynx. It involves the rapid production of: (1) /hʌ/ to assess vocal fold abduction (posterior cricoarytenoid function); and (2) /ʌ/ to assess vocal fold adduction (thyroarytenoid function).
Second, open the LDDK recording in Praat. Then select the beginning 3-5 seconds of the task, making sure to avoid the first and last 0.5 seconds of the task. To improve ease of interpretation, select "Intensity" > "Show Intensity"
Lastly, count the number of syllables, and divide by the total duration of the highlighted segment, then compare to age and sex norms. In this example, 32 syllables produced over the course of 5.69 seconds. 32/5.69 = 5.62 syllables per second. This LDDK within normal limits for this person's age and sex!
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Leeper, H. A., Millard, K. M., Bandur, D. L., & Hudson, A. J. (1996). An Investigation of Vocal Function in Subgroups of Individuals with ALS. Journal of Medical Speech Language Pathology, 4, 163-182.
Renout, K. A., Leeper, H. A., Bandur, D. L., & Hudson, A. J. (1995). Vocal fold diadochokinetic function of individuals with amyotrophic lateral sclerosis. American Journal of Speech-Language Pathology, 4(1), 73-80.