Not sure what you are hearing but it's not cavitation [ see https://en.wikipedia.org/wiki/Cavitation ].

It sounds like you have a suction leak which shows up under the increased vacuum that results from installing the suction side cleaner. Unfortunately, suction leaks are often hard to find . . . especially when the equipment is not in front of you. The only tip I can offer is that suction leaks ALWAYS result in openings (intermittent or not) in the piping & fittings between the pool and the suction intake of the pump. That includes the pump lid. Once you add the cleaner, it also includes the cleaner hose and fittings.

Sorry.