Changes in spectral measures and voice-onset time with age: a cross-sectional and a longitudinal study

In this study, we searched for changes in spectral features (during the sustained vowels [a] and [i]) and the voice onset time (VOT, of [pa] and [ka]) of the ageing voice. A longitudinal study (on 20 participants) and a cross-sectional study (on 265 participants) were conducted. The spectral parameters under consideration were: the difference in amplitude between the first and the second harmonic, the energy difference between the frequency band below 1 kHz and 2-4 kHz, and the energy difference between < 1 kHz and 4-5 kHz. The VOT was also measured. Comparing five age bands of men and women, the cross-sectional study revealed a stronger H2 relative to H1 for women above 60 years pronouncing both vowels [a] and [i]. A relatively stronger spectral level was found between 4 and 5 kHz in elderly men and women (60+) for [i] compared to young men and women (20-29 years). Significant differences in the longitudinal study were not identical to those of the cross-sectional study. After a time interval of 30 years, 20 men produced a relatively weaker 2- to 4-kHz part of the spectrum and the VOT became much longer. It was impossible to attribute the changes purely to the process of ageing. Situations and emotions also play an important role and contribute to the different findings of the two groups of participants under consideration.