Objective: Previous investigations demonstrated voice changes corresponding to menstrual cycle phases, but few explored longitudinal cycle-to-cycle variations. The aim of this longitudinal case study was to describe changes in acoustics, laryngeal kinematics, vocal effort, and ability to produce high soft phonation in relation to menstrual cycle phases over the course of multiple cycles in a single normally-cycling individual.

Methods: Data were obtained from a 34-year-old professional voice user who had self-collected daily videostroboscopy, acoustics, vocal effort rating, and high soft phonation tasks for 394 days. Data were analyzed by cycle phase and across time for all cycles.

Results: Cycle length ranged from 24–32 days. All metrics demonstrated high cycle-to-cycle variability (±2 SD or more). Greatest variability was during menses and luteal phases. The fertile window was the least variable and showed decreased glottal area index (GAI), asymmetry quotient (AQ), perceived vocal effort, and increased CPPS, consistent with previous literature suggesting “best” voice quality during the periovulatory period. Perceived vocal effort and f0 were highest during the luteal phase. GAI was lowest during the luteal phase, and higher during estimated day of ovulation (EDO), which contradicts previous findings.

Conclusion: This case study represents a unique, longitudinal data set demonstrating changes in phonatory characteristics across repeated menstrual cycles. In general, there was increased variability during rapid hormonal changes (menses, luteal phases) and less variability during hormonal stability (fertile window), suggesting that voice changes are sensitive to the rapid hormonal shifts. Future prospective studies should include multiple participants and concurrent hormone level tracking.