On a trip today, my 2011 Prius (141K miles) had a noticeably higher and strained pitch to it while >45 mph. I’ve driven this for 75K miles, so I’m familiar with how it normally sounds while accelerating. The difference was subtle, but seemed to be there. It even occurred while I was coasting around 55 mph. But I didn’t hear anything when at a stop. MPG for recent trip was average. No warning lights. It has been slowly starting to eat oil the last couple years, but I’d say only a quart every couple/few thousand miles, and this has not accelerated recently.
I don’t know that I specifically checked, but I don’t recall seeing that the battery was abnormal. I was on very level terrain
Interesting. That would explain, I think, it’s correlation with speed but apparent laugh of correlation with the load on the engine.
Just took it for a drive with a more mechanically intelligent family member. the noise is definitely there, and apparently Not correlated with the engine load. The noise would decrease down to about 25 mph, below which we couldn’t hear anything. We did some donuts in the parking lot, and there were no noises when turning.
Sounds more like a wheel bearing or a tire problem. I’d look at tires first - clean each tire off and look for uneven wear patterns, cupping or scuffing. I even run my hand across the tread to feel for anything out of place. If the tires look good it is more likely a wheel bearing. I just did one on my 2010. It sounds like an airplane taking off the faster you get and is quiet at slow speeds. You can sometimes feel these if you jack the car up and spin the wheel. You can also take the wheel off and turn the hub assembly by hand to feel for roughness. It should turn nice and smooth. Any roughness is sign of failed bearing. Let us know what you find out!
I had an example where pretty much none of the conventional-wisdom methods worked to find which bearing was at fault. Not the change-when-turning-right-or-left, not temperature, not spinning the wheel or the hub while jacked up, because that particular bearing felt no different from the others when there wasn't 3/8 ton of load on it. A four-channel wireless stethoscope made a positive ID in seconds flat, because it could easily pick up the sound while really driving the car, with all the bearings carrying their normal load.
