The effect of duration, fundamental frequency and spectral tilt in the perception of Turkish vowels

This study investigated the effect of duration, fundamental frequency and spectral tilt in the perception of Turkish vowels. Eight Turkish vowels, /ʌ/, /o/, /u/, /ɯ/, /ɛ/, /œ/, /y/, /i/, were synthesized by systematically varying the three parameters. Each of the synthetic vowels had two duration (60 ms and 200 ms), three fundamental frequency (118 Hz, 133 Hz, 148 Hz), and three spectral tilt (+6 dB/octave, 0 dB/octave, -6 dB/octave) values. A total of 288 isolated synthetic vowels were presented to 102 speech and language pathology students. The participants, who were presented the vowels individually through headphones, were asked to identify the stimuli as one of the eight Turkish vowels. The findings showed that although there was no significant interaction among the parameters, each of the three parameters had a significant effect on the identification of different vowels. Duration had a significant effect on the identification of /o/, fundamental frequency on the identification of /o/, /ɛ/, /œ/, and spectral tilt on /ʌ/, /u/, /ɯ/, /ɛ/, /œ/, /i/. None of the parameters were found to have a significant effect on the identification of /y/. Even though the three parameters together did not show a significant effect on the identification of all eight vowels, confusion matrices suggested that all of the parameters had an effect on the perception of the Turkish vowels.