My Prius IV with about 10K miles started to emit a high-pitched electrical humming sound under the hood when it was in Ready mode. It did not have this sound before. I opened the hood and found the sound was coming from somewhere around/under the engine area. I want to know if this is normal on Gen 3 Prius? I have seen post on the same noise in Gen 2 Prius but the posts (thread) stopped without a resolution.