To explain how the ear can recognize a vowel sound as the same vowel, even though it is sounded at different pitches, the idea of vocal formants is invoked. This is data Benade showing that an Ah vowel involves a similar envelope of harmonics when sounded at different frequencies.-To explain how the ear can recognize a vowel sound as the same vowel, even though it is sounded at different pitches, the idea of vocal formants is invoked. This is data　Benade showing that an　Ah　vowel involves a similar envelope of harmonics when sounded at different frequencies.