Whirring sounds coming out of the front side of the car

There are so many noises on your video, it's hard to isolate what is the problematic noise.

 

Maybe the gearbox is the original culprit. I'm not sure. The noise related to driving includes tires, gearboxes, engines, drive shafts, universal joints, bearings, etc. You can test, when driving at a certain speed on a clean road, change the gear to neutral, whether there is a change in noise, or whether there is a difference in noise when driving on different roads, and collect more information to determine the cause.

 

There might be some tools that can help.

One with a trade name of ChassisEar is a four or six channel receiver with remote clamp-on sound pickups. You can clamp the pickups on several suspected areas like the wheel bearings, then go for a drive, and listen to the receiver while switching its channels. This can give you a very positive and fast diagnosis of where the sound is coming from.

The NVH App, for a smartphone, can use the phone's own sound and accelerometer sensors, and knowledge of the car's gear ratios and similar data, to separate the signal into what strength of signal is coming from the different components. It comes from Prof. Kelly, also known on PriusChat for a lot of technical videos about the car.

An early, low-tech take on the same idea is just to pay a lot of attention to the pitch of the sound being heard at different road and engine speeds.

 

If it is not a gearbox problem, you can also try this, which is to check whether the toes of the lower wheels are deviated in order to eliminate this problem. After driving for a period of time, what will happen to the temperature of the tires or brake discs. Toe measurement does not need to go to the tire shop. You can measure it yourself. Use a tape measure at the same height from the ground to measure the distance between the front and rear of the tire. What is the difference? Both front and rear tires were tested. If it is less than 5mm, the problem should not be a toe problem.

 

In the third video in post #3, I think I hear the sound of interest, a sound with a recognizable pitch. It is helpful that the camera is showing the speedometer most of the time.

Having a keyboard nearby while listening, it sounds as if the pitch at 90 km/h is roughly B♭. Toward the end of the video, the speed is decreasing, closer to 80 km/h, though the camera moves away from the speedometer. The pitch of the sound seems to drop to roughly A♭.

B♭ in that octave is a frequency around 233 Hz, and A♭ is around 208 Hz.

Reducing 90 km/h by the same ratio comes to 90 ✕ 208 ÷ 233, or just above 80 km/h for the lower speed. That seems to correspond to the speedometer reading, which makes the case that this is a sound related to the tires, wheel bearings, driveshafts, final drive, or MG2.

Assuming this Prius has P185/65R15 tires mounted, for their effective circumference I am finding figures in the neighborhood of 852 (top hit in a Google search) or 855 (an old PriusChat post) revolutions per mile, or around 530 revs per km.

90 km/h is 0.025 km/sec or 0.025 ✕ 530 = 13.25 tire revs per sec (same as driveshafts and differential).

The Gen 2 final drive ratio spec (for US and Canada anyway) is 4.113, so MG2 is doing 54.5 revs per sec in the same conditions.

The sound pitch of 233 Hz is about 17.6 times the rotation rate of the tires/wheel bearings/driveshafts, and about 4.28 times the rotation rate of MG2.

When I had wheel bearings fail in a Gen 1, the pitch I heard was about 12.8 times wheel revs for a front bearing, 10.8 for a rear. That was for a Gen 1 though, and the Gen 2 has different bearings. The 12.8 ratio made sense given the arrangement of balls in that Gen 1 bearing.

The Gen 2 MG2 rotor is built with 16 permanent magnets arranged into 8 V shapes, as seen at around 10:15 in this video. So a sound with a pitch close to 4 times the MG2 rotation rate could be near an octave subharmonic of flux past an MG2 stator fault. But I have two reasons I wouldn't necessarily jump on MG2 just yet:

• From an actual MG2 fault, I would expect the pitch relationship to be pretty exact, 4.0 or 8.0 say, not something "close" like 4.28. Exact would be easy to explain, "close" would be hard. Of course, my arithmetic above was approximate in a lot of places. Suspicion of MG2 might justify being much more careful about measuring the pitch and speed and size of the mounted tires.
• Sound from MG2 would be strongest in the left of the engine compartment. I'm not there in person, but I notice the camera tends to move to the right, not the left, when trying to emphasize the sound.

I am still thinking if there is a mechanic shop nearby that has a remote sound pickup tool like a ChassisEar, that will make it easy to pinpoint the sound source.