Is there redundancy in the auditory system like there is in the visual system?
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!