imac beeps/meeps/chirps

I'm really hoping someone can help me. Apple Exec cannot, and suggests that I need a SSD and an electrician (which I already had my power tested and they know that).

Purchased 21.5" w/Retina in March 2016, 2TB, 16GB RAM in March 2016. It has beeped a low tone 1-2x every ten mins, regardless of where it is plugged in, online or off, etc. Apple has replaced the unit three times, along with another two hard drives. Every single one beeps. It is a single, low tone, not controlled by volume, it emits from the unit itself. Apple now insists that it is "environmental" and that I should purchase (downgrade) to a laptop with an SSD drive.

I've read some incidents where others have experienced the same issue and forwarded it to my contact on the Exec team, however, they tell me that they don't know how those cases ended up, so can't look into it. The "engineers" insist it's electrical, but cannot tell me what type of testing to have done. I'm about to return to Dell, since Apple has taken this "not my fault" attitude and is actually beyond being of help/service in troubleshooting their product. Please help!