The shop checked out a lot of the car, and the only thing they can find that explains the sound is that there was a loose seal near to the corner of the passenger door framing, and that a small amount of air is passing through. The sound does increase as speed increases, and decreases as speed decreases, so in that regard it does make sense. The sound does not occur if the car is not in motion (doesn’t occur when revving the engine). The sound, when driving home from the shop yesterday, is less noticeable then before. My friend could barely even notice the noise on the way home, and he was in the passenger seat. The shop spent a good half the day exploring the car, with numerous test drives, people in both the driver and passenger seat, and even opened the dashboard and area around the glovebox to see what the issue was, and that was the conclusion they came to, that it’s just a slightly cracked/loose seal around the passenger door frame.
Not sure if I’m convinced, but the car has shown no signs of issue or problems when driving. The transmission is a sealed unit–it was explained to me that this was why I couldn’t find a dipstick to test the level of the transmission fluid, because it was a sealed unit. I also have had no issue shifting (my car is manual as was previously stated), and if my transmission fluid was low or nonexistent it would most likely be more difficult to shift. I have heard no other types of noises or rattling. When I had a wheel bearing issue before I remember some rumbling, but there is no such noise this time. They tested brakes, batteries, all the fluids, and no issues were found.
Thanks for everyone’s inputs on this, for now I’m just going to go with it and see how it handles. Like I said I’ve had no real issues, and so I’ll just play it cautious and if I see anything else out of the ordinary, I’ll head in for a second opinion.
I will correct one mistake I made as pointed out by VDCdriver and that was the reference to the automatic transmission. I missed the “manual” part of your comment.
That being said, the manual transmission has a stick in the same location as an automatic transmission; down low on the passenger front side. The only difference between the manual and auto is that the auto is compartmentalized into 2 sections with one section holding gear oil and the other holding ATF (auto trans fluid).
Low gear oil in a manual transmission does not cause shifting problems except when the breaking point is reached and mainshaft bearings seize, the ring gear gives up, etc, etc.
I have no idea where the shop comes up with this idea of a sealed transmission with no stick. Of course it has a stick and a legally blind person should be able to find it with little difficulty.
Here’s a pic. Third from the left; yellow loop handle is the stick.
You’re dealing with a shop that can’t find the obvious???
^
ok4450 is correct (as he usually is), and I am really beginning to wonder about the OP’s “trusted mechanic”.
Has anyone checked the engine dipstick in order to make sure that the engine wasn’t overfilled with oil? If the trans/differential was drained, it is very possible that the engine’s oil was never drained and that there could be the dual problems of a dry trans/differential and a grossly-overfilled engine.
If the OP isn’t comfortable with reaching all the way down to grab that grimy little dipstick handle for her transmission oil, then she should have a different mechanic do so. I think that this is a situation that screams out for verification by another mechanic–preferably somebody who is actually familiar with the workings of Subarus.
(I’m a guy, just FYI 
and I’m not afraid to get dirty, just wasn’t able to spot where the dipstick was until I got that better picture) I was able to find the dipstick, thank you for that picture. Based on where it was showing it in my owners manual, it was a lot lower and more covered on the passengers side. I was able to get a reading and the level seems to be just fine, dipstick was coated to the “F” (even took it out, wiped it, reinserted, and then pulled it out again for a reading). The shop that I took it to yesterday, for the record, was NOT the mechanic that I had do the inspection 2 weeks ago. The mechanic I usually use is a very trusted source and I have had no issues with him ever. I went to this other group due to a recommendation from a friend about their service, and was unable to get out to my original mechanic because of distance–I didn’t know how far the car would go/last. They obviously don’t know much about Subarus, and rest assured I will not be going there in the future (asked them to top off the coolant, they said they did, and they did not). Regardless however, the transmission fluid seems to be just fine. My oil level was overfull, they found when they tested the oil level, so they did change that out yesterday as well. For now I think that’s really all I can do, other than see if anything changes.
"My oil level was overfull"
Did you find out if it was “overfull” by a quart or less (which isn’t really a problem), or whether it was overfull as in…twice as much oil as it should have had?
If it was really grossly overfilled, it is possible that the noises you were hearing were from inadequate lubrication resulting from a gross overfill of motor oil, and that could well come back to haunt you in the very near future. If you don’t know why too much oil leads to lubrication problems, please let us know and we will explain that issue for you.
Try to get some additional details!
What are noticeable signs that would be apparent if the oil was overfilled and it damaged my engine? I have not noticed anything out of the ordinary, and if it was overfilled to a point that it would damage my engine by foaming/aerating, I feel like I would have noticed something or seen signs of it.
The standard test for door seal noises is to tape the door shut on the outside and see if the noise goes away.
If the shop checked the oil level , found it to be somewhat overfilled, and didn’t do anything about it, I expect it is probably ok. What happens, fyi, with an oil overfill condition is the top layer of the oil gets continually pounded by the various rotating components inside the lower part of the engine (that usually just turn through the air, not hitting the oil). The oil gets churned into a froth with lots of air bubbles in it, and so it won’t lube the engine like it should. I’ve never had that problem so I don’t know if it would be readily apparent to the driver or not. A small amount of overfill won’t cause this problem, the manufacturer provides some lee-way.
Glad you seem to have the noise problem resolved. One thing I tend to do when I’m hearing unexplained noises and can’t determine the source is to remove everything from the car that I can, including the trunk, spare tire, and jack. Sometimes I’ll find the problem doing that. One time I found a golf ball had made it’s way into the spare tire well.
Edit: I was really surprised to learn your manual transmission has a dipstick. That’s a pretty good idea by Subaru. My Corolla’s manual xmission fluid level has to be checked by unscrewing a plug at the top of the transmission and sticking our finger in the hole to see if you can fill the top of the fluid.
“If the shop checked the oil level , found it to be somewhat overfilled, and didn’t do anything about it, I expect it is probably ok.”
George–The OP already told us that…
“My oil level was overfull, they found when they tested the oil level, so they did change that out yesterday as well.”
In response to that info, I asked “how overfull” it was, but so far…no response on that point.
If you still have a noise issue check the pulley bearings of the idler wheel used to tension the fan belt.