title: Acoustic analyses of thyroidectomy-related changes in vowel phonation.
abstract: OBJECTIVE
  Changes in vocal function that can occur after thyroidectomy were tracked with acoustic analyses of sustained vowel productions. The purpose was to determine which time-based or spectral/cepstral-based measures of two vowels were able to detect voice changes over time in patients undergoing thyroidectomy.
  
  
  METHODS
  Prospective, longitudinal, and observational clinical trial.
  
  
  METHODS
  Voice samples of sustained /ɑ/ and /i/ recorded from 70 adults before and approximately 2 weeks, 3 months, and 6 months after thyroid surgery were analyzed for jitter, shimmer, harmonic-to-noise ratio (HNR), cepstral peak prominence (CPP), low-to-high ratio of spectral energy (L/H ratio), and the standard deviations of CPP and L/H ratio. Three trained listeners rated vowel and sentence productions for the four data collection sessions for each participant. For analysis purposes, participants were categorized post hoc according to voice outcome (VO) at their first postthyroidectomy assessment session.
  
  
  RESULTS
  Shimmer, HNR, and CPP differed significantly across sessions; follow-up analyses revealed the strongest effect for CPP. CPP for /ɑ/ and /i/ differed significantly between groups of participants with normal versus negative (adverse) VO and between the pre- and 2-week postthyroidectomy sessions for the negative VO group. HNR, CPP, and L/H ratio differed across vowels, but both /ɑ/ and /i/ were similarly effective in tracking voice changes over time and differentiating VO groups.
  
  
  CONCLUSIONS
  This study indicated that shimmer, HNR, and CPP determined from vowel productions can be used to track changes in voice over time as patients undergo and subsequently recover from thyroid surgery, with CPP being the strongest variable for this purpose. Evidence did not clearly reveal whether acoustic voice evaluations should include both /ɑ/ and /i/ vowels, but they should specify which vowel is used to allow for comparisons across studies and multiple clinical assessments.
authors.affiliation: Audiology and Speech Center, Department of Surgery, Walter Reed National Military Medical Center, Bethesda, Maryland 20889, USA. Nancy.P.Solomon.civ@health.mil
authors.forename: Nancy Pearl
authors.initials: NP
authors.lastname: Solomon
authors.forename: Shaheen N
authors.initials: SN
authors.lastname: Awan
authors.forename: Leah B
authors.initials: LB
authors.lastname: Helou
authors.forename: Alexander
authors.initials: A
authors.lastname: Stojadinovic
mesh_terms: D000162:Acoustics; D000328:Adult; D000368:Aged; D000465:Algorithms; D000704:Analysis of Variance; D055154:Dysphonia / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010699:Phonation; D011446:Prospective Studies; D012815:Signal Processing, Computer-Assisted; D013018:Sound Spectrography; D013061:Speech Acoustics; D013067:Speech Perception; D013068:Speech Production Measurement; D013965:Thyroidectomy / Q000009:adverse effects*; D013997:Time Factors; D014833:Voice Quality; D055815:Young Adult