For a compact car, I do not think it is any louder then anything else on the market. My Previous vehicle was a 2012 Honda Civic EX and it was pretty much the same. The car is a great deal for the price, I went for the limited since it was worth it for a bit more money. It is not performance beast but it moves along just fine. I have 3K miles on mine now and I average 33.6 MPG- I think this is great for a all wheel drive vehicle.
I have 8,000 miles on my 2015 Impreza and it has been a great car for its intended purpose. Make no mistake though, it is not a powerful, quiet highway cruiser. It is a perfect around town or city car. If you drive on the highway everyday you will notice it is very twitchy at higher speeds and is very sensitive to sidewinds. It seems hard to keep it going in a strait line. Also, the Bluetooth/ touchscreen is terrible and slow. The front seats do not have a lot of legroom for taller people. All in all, the gas mileage has been very good, and it is reasonably fun to drive. My advice, get a base model because it feels like a $17,000 car, not a $25,000 car.
We never buy a new car but when shopping for an Impreza, low mileage used were always more than new. So we ended up looking for a new one, with acceptable colors and price. Never found much difference in price and shopped internet in 4 states. Never found the desired color in stock but winter was coming and wife wanted all wheel drive so we made the purchase locally with an acceptable color. I've been a "car nut" since the 50's and have owed many from a full race Pontiac to a Mercedes and BMW but never a Subaru. The Subaru Impreza drives with the best once you replace the factory tires with good ones. I don't find the noise objectionable even under heavy throttle. The body has some flex which was disappointing but not unusual. Car is well made and solid overall. Subaru produces vehicles in various models but the option list in each model is sparse so don't plan on adding anything later from Subaru. The CVT ruins the car for me but the wife still loves it. It requires a different type of driving. Maybe I'll get used to it eventually if my wife ever lets me drive it. Mileage is great with warmer weather. As with all vehicles, it's not great when it gets cold. About 37 MPG highway in the summer and 27 MPG for shorter travel. The vehicle mileage indicator isn't as smooth as other vehicles and is off between 6 and 8%. For an economy car with all wheel drive, the Subaru Impreza is a best buy.
I've owned 3 different cars in the last 10 years and I have to say the Impreza is one of the best ones I've owned. The ride is very comfortable, interior is extremely nice to be in, and the styling is very nice too. Currently I am getting 42MPG (mainly a highway driver). The car does not feel underpowered getting up to highway speeds however do not expect WRX acceleration or sounds.
This rather expensive minicar is made of very thin metal. in the first 1000 miles it has been in for dent removal twice and now has a third small dent due to the light weight metal body work. The four cylinder is probably best suited for driving on flat parking lots and definitely not suited to drive up any incline. Very noisy interior. Much louder than my full size truck. Just open and close the door on one at the lot and see what I mean. Disappointing car at best. UPDATE>>> In the month of February we were involved in a collision where our right front was hit by a mini truck at a speed of 30 MPH. our Subaru was declared a TOTAL and fortunately we had GAP insurance as the payoff was much less than what was still owed. I intend on getting a larger Subaru, the Outback or Forrester to replace the unimpressa. I should note that my wife purchased this vehicle as she is a nurse and wanted the "safest" vehicle to replace her 10 year old Volvo S80 T6. I did not "test drive" the vehicle and after she brought it home I then was able to "test drive" it. I read all the available info on the Impreza prior to her buying it and based on the written reviews I suggested that she get it. I have since been to the Subaru dealership and "test drove" the Forrester and Outback and these do not feel tinny as the Impreza did. NOTE: when I mentioned the totalaled vehicle the salesman asked "was your wife hurt?" I replied no and he said "that's due to the ability of the car to absorb the crash and the cockpit surrounded by steel protects the occupants". When I mentioned the crash was a 30MPH incident his reply was "see what I mean, she walked away from it" I think most vehicles can sustain a collision at 30 MPH without being declared TOTAL. At any rate these are strictly MY impressions of the vehicle and as I mentioned we are purchasing a Forrester or Outback to replace it.