First , I would want to know what the airflow setting is on the blower motor.

Next size of return(s).

To be clear, you have three 3 1/2 ton systems for a total of 10 1/2 tons?

How many returns for each system and their size?

IMO

thanks
are you talking about the speed? I think is medium
yes I have 3 systems one for the south side of the house and the other for the north side, other unit is for the upstairs rooms .
each system have one small return and a big return like 12" or larger not sure the size

Your duct work is probably undersized for the size of your three systems. The supply and the return could both be too small. Adding dampers is not going to solve your noise problem.

How many square feet is the first and second floors? What is your location? Who decided you needed 10.5 tons of cooling?

its a 4200 sq feet home, but shut man probably the upstairs is approx 1500 location is Flower mound TX..
when the house was built, but I think the builder I bought the house a year after the house was built ..
I have a few companies over but they are clueless the last guy was here on saturday charged me a bunch of money to do a tune up on the systems and add freeon 6 lbs for 330 I think he was a theft..

a guy that sells equipment told me that it could be the returns that I probably need it another return, that some times its like when you are blowing on a straw if you make it bigger less the noise..

He put 6 lbs in 1 unit? Was before/after performance different? Did he show you proof of performance change? Is guy a lone wolf or does he work for larger firm? Go after firm or see if you can talk to his supervisor? Could be fraud.

10.5-Tons is way too much for 4200-sf home.
That's an average of 400-sf per ton of cooling; under even tough heatload conditions when equipment is working properly 600-sf per ton will nearly always get the job done.

Because there appears not to be enough airflow through the cooling coils it would appear the units are not performing near their Rated Capacities.

All airflow needs to be checked with an anemometer to each room. The duct system should have a Manual d evaluation performed on them to see if they need retrofit work performed on them.

Also, I'd have a Home Energy Efficiency Audit performed on your home & do the cost effective retrofit-work. That should result in a reduction of required Btuh.

Room thermostats with SWING temp setting should be used to get longer runtimes & longer times between on cycles.

Here is a link that might be useful: Correct /sizing of A/C Equipment & Duct Systems