Paul, I didn't even know they were deaf. ;)
From the link below, a quote notes that in 8 WOMEN:
The singing sequences are slightly surreal, and extraordinarily charming within the larger context of such a singular work. What is most engaging about them though, is that
each of the actresses does her own singing - no dubbed-in professional voices.
http://www.the-trades.com/column.php?columnid=1427