Auditory similarity to other words in the neighborhood High frequency words are discriminated more easily. Words with many phonetic neighbors with more difficulty. Lindblom Table 1 here 2. As vowel duration in a CVC syllable becomes shorter, the extent of the movement towards the vowel target is reduced. This produces both articulatory and acoustic undershoot.
Speakers can compensate for the duration effects by increasing movement velocities.
Increasing peak velocities entails greater biomechanical power expenditure. Sundberg s work on singing Female opera singers can produce F0 values which greatly exceed expected F1 values, esp. for high vowels. Singers lower the mandible and raise F1 in step with F0 increases. Because of large coarticulation effects, there are no absolute invariants. Perhaps sufficient contrast can still be found.