Air Conditioning - Central A/C Unit Making Noises

A few weeks back, the central a/c no longer cooled the house, line outside was freezing over, but kicked on, etc. Called out a tech. The tech pumped freon into the compressor and filled system with nitrogen. Found leak at TXV, fixed leak and recharged system. Also vacummed down the system and recharged.

Now, the a/c works and is blowing cold air again. However, ever since he was out, it immediately starting making this LOUD vibrating like sound, off and on throughout the time it runs. I called the tech back, he said no way to no for sure but could be the compressor going bad but since it's sealed, no way to really know until it just goes.

Then today, it started making yet another noise, from the unit outside almost like an air compressor sound or something, hard to explain. The noise kicks on, then off again, etc. I just turned the a/c totally off because I wasn't sure what was going on with it with all those noises taking place.

Any ideas on what is causing these two noises to happen?

When your not there its hard To say whats what. Get him back to look at it. Does the compressor outside stop and start????when the noise stops???
Can he have it over charged. You can have lots of ifs ifs here. Sounds like he did the job right.

Compressor noises are never a good sign. You didn't mention the age of the system. It's possible you have a compressor going bad and that freeze-up may of had something to do with it.
I have noticed a connection between freeze-ups and compressor problems that don't show up until the near future, say a few weeks or so. I wonder if other techs in this forum have had this experience too.