Do you mean the aum/um sound?

"Need" to do it? Absolutely not...there is not just one method for exploration, there are many.

Strange, that's the first time I ever heard of that.

You are referring to the resonant tuning in the Gateway Course.  The tuning does not have to be particularly loud at all to get its effect.  You could achieve it easily in a room with the door closed, getting the effect using a soft humm. The idea is to feel and visualize it inside; a method to help relax you, change your modality.  It does not require volume for it to work.  It's effect may be variable.  Sometimes I really feel it, sometimes not.  The practices in the CDs are taken from many different practices including mediation techniques and QiGong for example all use vocal vibrational methods in some of their techniques.

Monroe does explain what it is for: ..."to help you vitalize and charge your entire system. It promotes an accel­­erated gathering of your vibrational energy while reducing your internal dialogue. In addition to preparing you for these exercises, you may use Resonant Tuning for meditation or quieting your thoughts..." - Monroe

Is it necessary?  Remember the energy conversion box, resonant tuning, the resonant energy ballon, and the affirmation are all tools.  You may find some tools more useful than others, and find you return to these tools differently over time.  You may also start with TMI's affirmation statement and find later that you have something else you wish to say.

When you put them all together you will find yourself practicing a ritual; yes... a ritual, like that practice by many religions.  The ritual helps one mentally prepare for the task, get in the mood, the state of mind where it may begin.  But like all rituals, they are there to simply help set the stage.  The problem with rituals is thinking they in themselves are some sort of path, formula, recipe for OBE; if reproduced correctly one will manufacture the desired result.  That's the problem with people and rituals, religious or not.

After awhile you may not need all the tools, the rituals.  It's a matter of what works with your personality, your style.  But as others have noted it is not an "essential" tool.  You will likely find by the end of all 6 CD sets, that you have developed your own personal ritual and find how much of it you need or have outgrown.  Even Monroe believe the goal was to get beyond all the tools, to have broadening your own daily conscious' awareness.  It is not just about OBEs. You don't have to go anywhere to connect.

I would say, the absolute skill one needs is to learn to clearly observe your mind, to become highly focus in that mindfulness so one can clearly apprehend and catch oneself adding to the experience, recognizing what thoughts are your own, what thoughts are coming from something that wishes to communicate with you. Then begin able to do this all the time. 

Off hand from what you say, the humming may not be the big problem.  If the roommates are that close, humming or not, you may have a hard time finding yourself able to tune "them" out.  What you need is to be distraction free.

As an aside, the new tuning sections in Wave 5 and 6 are much better than the ones in the first CDs.  Also, I would suggest not letting the resonant tuning keep you from moving forward with the lessons.  Also, don't worry about all the imagery that the lessons take one thru.  They too are tools.

Note also, you don't need to leave your body to make contact.  If that's what you're expecting, you're already stuck in dogma and limiting yourself.

Thanks,

- B