Letting them hear each other or even see each other should not keep them from talking. You could try letting them be in the same room together once in a while to see how they get along in their cages and even let them play outside their cages together if watched closely especially at first.
The main problem people have when having two birds of the same type is that sometimes the birds bond to each other instead of their human counterparts. This will usually only happen if the birds are kept in the same cage. Then the bird will be less likely to want as much human interaction and will instead rely on their birdie buddy for companionship. If you have the room and have plenty of time to spend with your birds keeping them in separate rooms is great until they are trained and beginning to talk or whistle but supervised interaction with each other should not stunt the training process. Instead it should just provide more time for companionship.