There are some CH silencer products such as "Tower Triple X Silencer".
(The manufacturers witter on about it being fine to have both the silencer and their inhibitor in your system indefinitely. So it is clearly a specific product and not to be confused with inhibitor(s).)
I have used the sentinel equivalent products in the past (i.e. prior to changing the boiler and going sealed system)... typically the old boiler would start clanking and banging, and a dose of noise reducer would keep it quieter for a year or two.
They notionally reduce scale (i.e. hard water deposits), however unless you are frequently adding new water to the system, then there should only be a finite amount of that to come out of solution in the first place. Needless to say that if that amount does cause a problem, any product that attempts to dissolve it has the limitation that it can only do so back into the system water - it can't actually remove it from the system altogether, so there is the opportunity for it to redeposit again in the future. It may be they are also good at lifting deposits of magnetite and other anaerobic corrosion products that may tend to coat high temperature surfaces.
"Silencers" are supposed to lubricate pump bearings and suppress cavition effects. (Water vapour bubbles forming and collapsing in the system [pump & boiler]).
Sounds bollix to me though. I have never noticed any effects.
Adding a couple of these will do the same job:
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