Visual speech-feedback training fails because identical percepts can have different sound traces
Evidence
Alexander Graham Bell, a teacher of the deaf like his father before him, used the phonautograph to train his students to visualize the sound they could not hear. Many students could not speak understandably; since birth they had lacked auditory feedback from their own voices. Bell’s idea was to train them to reproduce phonautograph signatures recorded from ordinary speech. If the signature looked right, it would sound right! This is actually true; however, it is too restrictive—many sounds with different-looking sound traces are perceptually nearly identical. Worse, the normal variations in physiology might make the sound trace for the vowel sound “ohhhh” in subject A impossible for subject B to reproduce, yet both are recognizable as the same vowel. The concept Bell really needed was years in the future: formants, which are broad ranges of enhanced frequencies in the voice that define different vowels (see chapter 17). — Eric J. Heller, Why You Hear What You Hear- An…, 465
Categorization
Category: Causal Relationships
- DEFINE: Introduces how reading sound traces is limited and foreshadows the key role of formants.