Acoustic analysis
voice
After a deep breath, a sustained vowel /i:/ was pronounced. The voice was recorded for analysis after collection with a microphone (Yamaha UR22C-R-PACK, Japan) at a 45° angle positioned 5 cm from the patient's mouth. The voice records were analyzed using the phonetic application (PRAAT v6.2.19. Phonetic Science, University of Amsterdam, Netherland), which measured jitter and shimmer for each patient. Jitter refers to the short-term variations in the fundamental frequency, and shimmer represents the short-term variations in the amplitude of sound waves between contiguous glottal cycles.