I drive a Skyactiv 2013 Mazda 3 2.0 Liter MT 65,000 miles, and recently bought a 2023 CX-5 NA AT bought new, now at 10,000 miles. Over time I noticed pretty much the same noise with the same characteristics in both vehicles. I get to maybe 45 MPH ish, and I hear a whine that slowly raises in pitch with speed.

Both cars drive perfectly normal. Seems unlikely that it’s an issue since both cars do it. I’ve read a post or two where people took their cars to the dealership and they said it was a normal sound that the alternator makes. Interested to see if anyone else experiences this with their car, or has any thoughts on it.

Thanks for reading, love the subreddit everyone!