Hello, I have a 2014 Dodge Grand Caravan with 45,000 miles. It’s making a strange noise at random times when stopped, or during or shortly after acceleration. I don’t know how to explain it other than it sounds like the opening of a very large hatch, or a very large piece of metal swaying in the wind attached to a large ship or piece of equipment. It doesn’t always happen when I’m turning either. It’s a very deep, eerie, and haunting sound, almost like a tuba, that trails off, last just a few seconds, comes ago a few times a week on average. The vehicle doesn’t really feel different when it does that, but it seems like it may be coming from the right front somewhere deep. It sounds like I’m turning a large ship is what the sound reminds me of, or the horn of a large ship in the distance. I’ve had it checked out, and of course it only happens when I’m driving it. Maybe something is rubbing. Very strange! Thank you in advance!
Did it always make this noise or is it a fresh benefit of owning a dodge?
If you just bought, and it has that noise, it could be virtually anything - they might’ve forgotten a wrench somewhere inside the frame. Not as ridiculous as you may think.
Somebody had a rattle in the 70s in a new car. After quite some time they took the door apart and it was a can or bottle in the door with a note from a factory worker saying something to the effect of I know you would find this some day!
Wow! I did buy it this past spring from a car dealership. You’re probably on to something then. I’ll have that checked out. Thank you! 
It’s like a time capsule! 
It could be a pain to locate. I suggest buying a set of diagnostic microphones - they are pretty cheap on ebay - something like this High Sensitive Electronic Stethoscope Kit Noise Diagnose Scope Mechanic Tool Set | eBay.
There is a really good chance you’ll need them more than once.
The noise is from the air conditioning expansion valve located at the firewall on the right side. The sound occurs when the pintle valve controlling the refrigerant flow inside the valve vibrates, it is a nuisance, won’t cause harm.
As to assembly line mischief, each part and each assembly line step can be traced so those stories of 50 years ago are a thing of the past.
OP, pretty good descriptive prose there. Maybe take up writing novels? … lol … no idea what’s causing it in your case, but my fairly new refrigerator occasionally makes a similar noise. New tech refrigeration apparently is sort of like a sound machine, you wouldn’t believe all the weird sounds it makes, sizzling, rhythmic thumping, whirring, groaning, a sort of sound fiesta. Keeps the beer nice and cool, so no complaints … lol …
Thank you
My (almost) new refrigerator uses iso-butane as the refrigerant. Thinking the weird noises I hear now (compared to 40 year old fridge) are due to technology switching to that instead of older freon-type refridgerant. Wondering, do cars these days use iso-butane type refrigerants in their AC systems as well?