Noise at 27-28 MPH, 2006 Prius

2006 Prius, 115,000 Miles, Start battery just replaced after 9 years, drive battery original.


Noticed a new noise, like a chirping noise, similar to the bake noise when you press the brake peddle hard and they chirp. Was told this is normal and was some pump noise.
This moving noise appears at 27-28 MPH. It appears generally on almost flat roads. It appears with the engine is running @ 1184 RPM + or -, 0 RPM when the electric motor is moving the Prius/Gas engine off, cruise control on or off.
Appears to be coming from the front of the car. I thought it might be a nail in the tires, or wheel bearings, but no nails are found and the tries are balanced and rotated every 5,000 Miles.

Anyone have a similar noise or any suggestions. Just had a Toyota mechanic take a ride, and he thought it sounds like the HV system trying to maintain the speed, sort of adding and reducing tork. At least that was what I gathered from his comments, but said its safe to drive. Another noise, like engine noises associated with the Prius that we all have accepted as part of this type Hybrid system.