Dysphonia Severity Index

Voice quality of patients and healthy volunteers was measured using the Dysphonia Severity Index (DSI), recorded with a head microphone and audio interface (Focusrite Scarlett Solo, United Kingdom), and the analysis was performed using the PRAAT software (version 6.0, University of Amsterdam, The Netherlands). 22 The DSI consists of the highest frequency (Hz), lowest intensity (dB), maximum phonation time (MPT)(s), and jitter(%). We used a head microphone, with a smaller mouth‐to‐microphone distance compared to a table microphone as used in the original study, 23 therefore we applied a translational factor of −7.5 dB on the lowest intensity. Total score was calculated according to the original formula, with a lower score representing a worse voice. 22