Increasing evidence exists that poor speech perception
abilities precede the phonological deficits typically observed in dyslexia
, a developmental disorder in learning to read. Impaired processing of dynamic features of speech, such as slow amplitude fluctuations and transient acoustic cues, disrupts effortless tracking of the speech envelope and constrains the development of adequate phonological skills. In this study, a speech envelope enhancement
(EE) strategy was implemented to reduce speech perception
deficits by students with dyslexia
. The EE emphasizes onset cues and reinforces the temporal structure of the speech envelope specifically.
Design: Speech perception
was assessed in 42 students with and without dyslexia
using a sentence repetition task in a speech-weighted background noise. Both natural and vocoded speech were used to assess the contribution of the temporal envelope on the speech perception
deficit. Their envelope-enhanced counterparts were added to each baseline condition to administer the effect of the EE algorithm. In addition to speech-in-noise perception, general cognitive abilities were assessed.
Results demonstrated that students with dyslexia
not only benefit from EE but benefit more from it than typical readers. Hence, EE completely normalized speech reception thresholds for students with dyslexia
under adverse listening conditions. In addition, a correlation between speech perception
deficits and phonological processing
was found for students with dyslexia
, further supporting the relation between speech perception
abilities and reading skills. Similar results and relations were found for conditions with natural and vocoded speech, providing evidence that speech perception
deficits in dyslexia
stem from difficulties in processing the temporal envelope.
Using speech EE, speech perception
skills in students with dyslexia
were improved passively and instantaneously, without requiring any explicit learning. In addition, the observed positive relationship between speech processing and advanced phonological skills opens new avenues for specific intervention strategies that directly target the potential core deficit in dyslexia