Weird noise above 40km/h from electric motor not usual

Hello guys I am an owner of a 2008 Toyota Prius with 160k kilometers on the dash. My car is making a really weird noise above 35-40km/h and it just gets louder when accelarating. The noise is like the noise the electric motor has but much louder and deeper. It does it when accelarating or even if you let off the gas until it reaches below the above speeds. I have had the dealer here in Greece diagnose it but they say they can't hear anything wrong. They checked wheel bearings, water pump, inverter pump and everything that could be associated with the sound but they found nothing wrong. If anyone has an idea just say it because I am frustrated with this sound (and because it sounds expensive). For any more info ask me below so that I can help you. Sorry if my english are bad

 

Of course I will make a recording when I return back from my holidays!! Thank you very much I wish that we can sort this out.

 

Hey thanks for the answer! As soon as I return I will do a full service on the car anyway so I will of course look at all the things you mentioned. I am sure that they are not any leaks from the trans or the engine (so I don't think that the trans fluid is low) but I will check again just to be sure. But the CV joint might be the answer because I was also thinking of that. The tires are due to a change in a couple thousand kms but the tread is even on all corners. So to be clear I will change and inspect trans fluid, inspect CV joints and check the tires again.
Are Toyota Prius of our gen known to get bad CV joints or problems to the trans in the mileage my car has? (160k kilometers or 99.500 miles). Thank you!!

 

Alright guys I have taken the car to 2 dealships here in Greece no one can figure out what the issue is with the car. I also did a trip which was about 1400kms without ANY problems at all and without the noise getting worse or something. The car operates just fine but I can't live with that noise. I tried to shoot a video so you can hear it but it's difficult to hear it through my phone. I will try with another one. My last hope are the tires and I will change them putting some Turanza T0005. Everything you can suggest might help. Dealers here in Greece have no idea about our cars even though there are a lot of Prius especially 2nd gen.

 

Look, I am not a musician and I can't understand if you are talking serious or not :'). The sound starts at about 30-35km/h and around 45-50km/h it gets full volume. I drove the car at speeds around 150-160km/h and the noise didn't change volume or pitch at all. Happy to answer all the questions I get so that I can get my Prius fixed!

 

Alright guys I am back after a long time but i found what the issue was. Well I had an inner front right bad CV boot which caused the CV joint to loose lubrication and contain road dirt and thats why the noise I was talking about was made. I bought a full set of CV boots directly from Toyota for about 90 euros for each side which had lube, clamps and both CV boots for each side. The originals lasted for 15 years so I said why I dont buy the originals again so they last as long and not worry about anything.

 

Finally solved the problem guys. I found out that the noise was a bad front left wheel bearing. Quote from the dealer almost 700 euros, 660 to be exact, because they say that the bearing might be stuck in the hub and they will have to change the hub, the wheel bearing and the brake dust shield. If the bearing isn't stuck in the hub I think it will be at around 200 euros. You can now have a taste about Greek Toyota Dealers as well (they needed almost a year to find where the noise was coming from and then they quote a huge amount of money).