The unit vibrates and has a pulsing sou...

These things tend to make a bit of noise, some more than others. You will not be able to do much about the internal produced noise but you can do a lot with the resulting vibration noise.
While the unit is running, take a few minutes and actually touch the unit ALL OVER, you are listing for any vibration noise to cease or be less so where you are touching. This includes the collection pan and the filter. Slightly Tilt the unit in all directions. Make sure that the door to the collection pan is closed properly. Take a few strips of the peel-off adhesive sided thin window/door insulation and apply to the bottom of the collector pan, if it sits ON the bottom of the unit. Place an inch or two thick blocks of foam rubber under each corner of the unit. Make sure the unit is level. Some where along here you will stifle some of, or maybe even most of the noise.
Good luck. :)