B.R., Rhode Island
It sounds like you do have some of the older air-pressure toilets because a common complaint was about the flushing noise. The good news is that over the years most air-assisted toilets have been redesigned and they now flush at a much lower noise level.
I would not recommend trying to rebuild or convert your existing toilets. Replacement with a modern “high efficiency toilet” should be your best option. But, since you are dealing with three toilets I know that replacing all of them at once can be costly. So, try changing just the toilet(s) used in the bedroom area and leave the toilet(s) used mostly during the day in place. Reducing the loud “jet-flushing” sounds at night should give you and your family a first class ticket to snoozeville.
Master contractor and plumber Ed Del Grande is the author of the book “Ed Del Grande’s House Call” and the host of TV and Internet shows. Visit eddelgrande.com or write firstname.lastname@example.org.