Higher formant normalization results from auditory integration of F2 and F3.

Two experiments were conducted to test the hypothesis that higher formant normalization results from the auditory integration of F2 and F3 when they are within 3 Bark of each other. In the first experiment, Formants 3-5 were manipulated in both a "hid"-"head" continuum (in which F2 and F3 are within 3 Bark of each other) and a "hood"-"HUD" continuum (in which F2 and F3 are not within 3 Bark of each other). It was found that there was a shift in identification consistent with the higher formant normalization effect only in the "hid"-"head" continuum. In the second experiment, F3 alone was manipulated in a "hood"-"HUD" continuum. The amplitude of F3 in this continuum was increased (as compared with the F3 in the "hood"-"HUD" continuum used in Experiment 1) and a pretest indicated that the shift in F3 could be detected. As in the first experiment, there was no shift in identification associated with shifting F3 frequency in a back-vowel continuum. The results of these experiments are not consistent with an explanation of higher formant normalization in which hearers adjust an internal vowel space in response to higher formant information; rather, the present findings indicate that higher formant normalization results from auditory integration of F2 and F3.