title: Voice loudness and gender effects on jitter and shimmer in healthy adults.
abstract: OBJECTIVE
  The aim of this study was to investigate voice loudness and gender effects on jitter and shimmer in healthy young adults because previous descriptions have been inconsistent.
  
  
  METHODS
  Fifty-seven healthy adults (28 women, 29 men) aged 20-40 years were included in this cross-sectional single-cohort study. Three phonations of /a/ at soft, medium, and loud individual loudness were recorded and analyzed using PRAAT software (P. Boersma & D. Weeninkk, 2006). Voice loudness and gender effects on measured sound pressure level, fundamental frequency, jitter, and shimmer were assessed through the use of descriptive and inferential (analysis of variance) statistics.
  
  
  RESULTS
  Jitter and shimmer significantly increased with decreasing voice loudness, especially in phonations below 75 dB and 80 dB. In soft and medium phonation, men were generally louder and showed significantly less shimmer. However, men had higher jitter measures when phonating softly. Gender differences in jitter and shimmer at medium loudness may be mainly linked to different habitual voice loudness levels.
  
  
  CONCLUSIONS
  This pragmatic study shows significant voice loudness and gender effects on perturbation. In clinical assessment, requesting phonations above 80 dB at comparable loudness between genders would enhance measurement reliability. However, voice loudness and gender effects in other age groups, in disordered voices, or when a minimal loudness is requested should be further investigated.
authors.affiliation: Head of Speech Pathology Section, Clinic of Otorhinolaryngology, Head and Neck Surgery, University Hospital Zurich, Frauenklinikstrasse 24, 8091 Zürich, Switzerland. meike.brockmann@usz.ch
authors.forename: Meike
authors.initials: M
authors.lastname: Brockmann
authors.forename: Claudio
authors.initials: C
authors.lastname: Storck
authors.forename: Paul N
authors.initials: PN
authors.lastname: Carding
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Drinnan
mesh_terms: D000328:Adult; D005260:Female; D006685:Hoarseness; D006801:Humans; D008144:Loudness Perception; D008297:Male; D010700:Phonetics; D011571:Psychoacoustics; D012737:Sex Factors; D013061:Speech Acoustics; D014831:Voice; D014833:Voice Quality