Can you ID this noise after shutdown?

Yesterday my 2008 Prius with 95,000+ developed a new noise after turning it off and it has me a bit worried. I took an audio sample, can anyone identify this? Last night it occurred for like 5-10 minutes. Now today I went to turn it on and before I even pressed the power button it made another noise that I've never heard before which I didn't get on audio. It turned on fine, I let it run for a few minutes and then shut it off and the noise I got on audio occurred for several minutes. The noise comes from the driver's side by the electric motor. The clip should play in iTunes or Winamp, took it on my iPhone so its kind of low in volume.

 

Well, it's definitely something to do with the brakes. Usually my wife drives our Prius so I drove it today (she has a longer commute and this was the 1st day after she told me about the noise). The noise actually occurs while driving as well. I heard it both the entire trip to and from work today. After shutting off the car it does it's "noise thing" for a while; the length seems to depend on how long its been driven. It almost sounds like steam going through the system when the noise is idle. I took a few videos when I got home that have better audio (dismiss the video!).........can't post even embedded urls yet....will try again later.

I appreciate the responses so far.

 

With all respect I don't think this noise is a normal one, I've had this almost 5 months now and know the normal thermos noise after shutdown.

Again, this happens while driving and after shutdown. This first video starts with the car running so you can't hear the noise too much but around 1min into the video I've shut it off and get better audio. Notice how it's pretty loud and regular. At 1:30 I press & hold the brake while the loud noise is happening and it takes the noise down to the volume it makes while driving.

Prius Videos - Pearson Imaging Photo Galleries

The second video in the gallery is what it sounds like from the outside passenger side. When the clicking noise isn't happening it sounds like steam moving through, like a hissing sound. After locking the car all noises stop after a few minutes (haven't timed it exactly).

Any help would certainly be appreciated!

 

Thanks for taking a listen Patrick.

Funny thing, I can't test it now as it didn't make the noise at ALL today?! I was baffled because it was regular yesterday and the day before when it started. We'll see tomorrow though.

Based on yesterday I would say it comes more from behind the engine by the firewall. It was very apparent in the car stopped. As far as operating modes, definitely in READY mode and IG-OFF for several minutes. My commute is only like 10-15minutes and when I pulled in I had plenty of time to grab my camera record the video and poke around. Tested the battery too and that seemed within normal specs but slightly low end due to this noise happening for so long.

Because the noise gets more quiet when I press the brake I'm guessing that the accumulator pump completely died and now just doesn't work. But I have absolutely no warning lights on the dash. My wife also told me today that just before the noise started for her when she was braking it wasn't smooth like normal, it kind of rumbled a bit.

I still need a chunk of time to download the repair manual from TIS so I won't have official troubleshooting for a while.

If it is the brake accumulator pump that died does it make sense I can still brake? I'm sure there are safety measures in place but what does it do? My coolant and brake fluid levels are right on. I don't notice any difference in braking...but again my wife drives it more.

 

Definitely the brake pump, it did the noise when I tried pumping it. I experienced the noise today a few times but nothing regular.

What's confusing me is that it's not throwing me a DTC. I would think that driving around in basically a computer on wheels it would tell me something big like this, even if it's a minor issue.....braking is a MAJOR safety issue! Again, I don't have the repair manual yet so I can't reference anything.