Odd buzzing noise near inverter/fusebox

2005 Prius almost 296k miles and about last week I started hearing this buzzing noise. It's not the AC system like compressor since my condenser is destroyed and coolant leaked almost 3 years ago, haven't fixed it and blower motor was not even on. Definitely not the engine either. Noise seems to be coming behind or around fuse box. Inverter pump died around 275k miles but replaced it no problem. I was thinking this could be the culprit, but when my pump blew, I smelt burning plastic for 2 seconds and then the car shut off. However, this noise is starting to bother me. It sounds like an ambient fridge in the cabin but it's louder when approaching the engine bay.

It's not the brake actuator, doesn't seem like any fuses are blown (which wouldn't make this noise anyways, never did before), and hybrid battery is fine. 12v is relatively new, replaced a few months ago. Have not noticed any drop in MPG, still getting around 40-45, with no problems accelerating. I hear this sound in both ready/aux or accessory mode while car is idle or while driving. I cannot find any information online about this so figured asking here. I should also add, the inverter "electronic humming" is still there, so this seems like it is a separate sound.

 

Small update: upon further inspection, I think it's coming from the inverter pump. I touched the insulated tube and it's vibrating, maybe a bit harder than usual? Would this mean that the pump is failing possibly? Coolant level overflow seems fine and within levels, didn't need to open cap for turbulence since I can see liquid moving through the container.