Could be almost anything given that description. A guess might be that it's for external lighting (or perhaps something for the garage). It may be a rather oddly placed disconnect for something as well.

is it buzzing?

Is the noise a hum of this frequency?

Here is a link that might be useful: 60 Hz

From memory there is a hum. If no one is talking the noise can be heard . It sounded like the sound form the link above but not nearly as loud.

I will go to the open house agin this weekend . I will try to get a video

I am concerned that this unit which is the model unit might be paying for the electricity for the outside lighting.

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" am concerned that this unit which is the model unit might be paying for the electricity for the outside lighting."

No worries. If you own the junction box, you can disconnect what ever is powered by it. :-)

"I am concerned that this unit which is the model unit might be paying for the electricity for the outside lighting. "

For a brand new unit this is highly, highly unlikely. Maybe the lighting just around your unit, but not everyone else's.

Any chance you can get a pic of this box?

Picture of the Breaker box and Square D box

That pic is, unfortunately, not that helpful. If we could read the labels and see the cable type....

Is there just the single cable entering?

That could be a motor controller. Unusual in residential situations.
If your request is serious, why did you not post any information from the nameplate on the unit?

That is a motor controller or contactor. Both relay type switches for switching heavy loads with light weight switches.

If on they definitely can hum.