AJ, thank you for posting to alert us about the potentially dire health risks associated with nMP ownership.
Anoxia can lead to brain damage or even death! Prolonged breath-holding, while straining to hear the fan, poses a serious work-place hazard. It is also possible that your continuing inability to hear the fan indicates that you are already suffering lasting harm from another insidious risk to which you alluded: deafening silence.
If this condition persists (or worsens) think of the consequences. Do you have spare time to learn sign language right now without seriously cutting into productive work time? Even if total deafness does not ensue, prolonged sensory deprivation can lead to psychological problems and is considered a form of torture.
I was going to selflessly come to your aid by offering to take this dangerous system off of your hands (I would even have paid for shipping). Then I realized that your workspace would be even quieter without the nMP and increase your risk. In that light, my offer might not be so clearly beneficial to you.
If a keg and a case of vuvuzelas outside your window would help, perhaps some members of this community would bravely come to your aid by making some noise.
Until a more permanent solution is found, please take steps to protect yourself: play bongos; rip out the new carpet and learn to tap dance; leave a vacuum cleaner or hair dryer running on or near your desk. However you do so, please find a way to use the system safely and keep us informed if you come up with workable solutions to these problems.