sewing machine should not be that loud ......... many things can cause the noise ....... first to do is to take it into a shop for a deep cleaning ....... they will clean, oil and check it out to make sure no gears are bend our wore out that is making that noise.
I was told to take my machine in every 6 months for cleaning since I use it a lot.
Agreed with those who suggest cleaning, and oiling it....it really shouldn't be making too much noise if it's well maintained.
Unless it's an old machine....they are naturally noisy.
I also use a mat underneath my sewing machine, so it's not directly on the table. It helps absorb any noise, or movement.
Put a thick cloth under the machine itself, (between table and machine), which should help dampen the vibrations and noise some more. Might also have a radio playing music to mix in, doesn't have to be loud, just to soothe the sound effects.