I came across this post looking for an alternative as well, such as brass fittings. The dielectric couplings installed are very noisy with water flow. These are exposed pipes in a loft style apartment, I rerouted two separate pipes replacing a galvanized section with copper in each (actually had a plumber come in as the work had to be by a licensed plumber).

Insulating the pipe has not worked. These are the common plumbing feeds between apartments and it has caused us to literally lose sleep.

How can I quite these things down? The noise is emanating at each dielectric coupling like a loudspeaker.