The air flow in your house is the most important aspect of your heating and AC comfort. If the airflow FROM the furnace/air handler (supply registers) and the air flow TO the furnace/air handler (return registers) isn't correct, you will have more problems.
The air flowing from all the supply registers has to find its way to the return register without and obstruction. Usually the return is located in a central area of the house that connects to each room and its supply register through hallways. Sometimes individual rooms may have both a return and supply register in them.
Not knowing the layout of your house, it's difficult to give you good advice other than follow the basic design ideas I mentioned above.
Now for some help. I will assume the current return register is located in the TV room and that is the best location due to the layout of the rooms. If there is another return, please tell me.
I would start by trying to mitigate the noise from the return in the TV room. There are 3 ways "noise" is transferred to a register. One way is the mechanical noise of the blower and motor along with any vibrations at the air handler can easily travel along metal ducting. Those same mechanical noises also travel through the air itself. The last "noise" is the whistling sound caused by the speed of the air entering the return register.
To mitigate the mechanical vibration noises, feel the furnace/air handler when the blower is running. Is there excessive vibration? If so, have the blower wheel replaced... it may be badly out of balance. If the vibration is not too bad, see if you can slide rubber mat under the furnace so the sound doesn't resonate with the hard floor.
If you have metal ducting, see if you can replace a 6' section with flex ducting. The flex will not transmit the mechanical noises. Make sure you use big enough diameter flex ducting.
If the return duct is a straight line from the TV register to the furnace/air handler, see if you can introduce a very gentle 90 degree bend. This can easily be done with flex ducting. This bend will absorb mechanical vibration that's transmitted through the air.
If your noise is whistling then you need to increase the size of the return register itself. Air flow is measured in cubic feet per minute (cfm). You have to have a certain cfm for your equipment to operate correctly so don't change the settings. If you install a bigger return you'll probably want to make the ducting from the return to the furnace/air handler also bigger. Many times installers always have too little return registers.
Hope that helps... good luck