There is certainly redundancy in the auditory system, well demonstrated by Gal Chechik et all
It is also clear that there is pronounced intersensory redundacy, involving auditory systems here
Another article discusses clear auditory redundancy in adults when participating in a task to discriminate between two sounds as quickly as possible
...the auditory system maintains and tolerates functionally independently represented redundant and contradictory predictions.
In terms of redundancy in development, it seems there have been shown links in mice discussed by Dr Thomas Braun
Hope this helps!