Vocal tremor and psychological stress

This study examines vocal tremor and its decrease in high versus low experi mentally induced stress situations. We have analyzed the Amplitude Tremor I ntensity Index (ATRI) and Frequency Tremor Intensity Index (FTRI) from the prolongation of vowel /a/ for approximately 5 seconds, under baseline condi tions and under 3 different test conditions (reading of tongue twister, rea ding of tongue twister with delayed auditory feedback [DAF], and spelling o f alphabet in reverse order), in a 2-test series, with and without demandin g experimental instructions (Experiments 1 and 2, respectively). Inclusion of experimental instructions was considered as making the first test situat ion more stressful than the second one. Our results show a significant decr ease in the ATRI variable when reading a tongue twister with DAF in relatio n to the baseline for the first test but not in the second, which suggests a suppression or significant reduction of amplitude tremor only in high-str ess situations.