underlying noise

I am using Audacity 2.4.2 windows 10. MXL 2008 michrophone. micro power PS400 transmitter. older HP lap tap (6 years)
I have just set up my voice over equipment in an a dry walled, with noise prevention insulation, and covered with stretch lycra fabric. the room is totally quiet with no external noise. When I turn on a track and record nothing, just to see if I hear something immediately, the track is totally silent. However, when I push record and begin to record, and then play back the recording there is a noise that sounds akin to swimming below surface in water. I have tried everything recommended in the manual re: noise reduction, some of the noise is reduced but not nearly completely. when I export the track and transfer to my email low noise is still there. Oddly when I recorded in a large room rather than my new booth I did not experience this problem. that room had its other issues for quality but this noise was not present. any suggestions?
thank you in advance for your time

Is that the Behringer PS400 (Phantom Power Supply)?
How is it connected to your computer? (The Behringer PS400 only has “XLR” out which is not directly compatible with a normal computer.)

Do you have a “Devil’s Adapter?”