2017 noisier than 2012?

I have a 2017 that makes a similar noise to what you've described. The caveat to this is whether the car is in gear or not. The second generation Volts have a pedestrian alert system that emits a rather obnoxious (in my opinion, take that for what its worth) howl at low speeds, or at a stop when in any driving range. It can sound similar to a fan running from what I have observed. Placing the vehicle in park while in an enclosed area with the windows down should confirm whether this is the source of your noise. Once in park, the sound should stop. As for road noise, several people here have commented about the same issue. In my experience, the car is quieter when on certain types of asphalt (recently paved black-top for example is whisper quiet). However, older roads, or concrete pavement (like what is found on many interstate highways) tend to be much louder in this generation. I'm not sure if this is due to tire construction, or if GM used different/less sound deadening materials from the first generation though.