Almost every since we have had our 2005 HAC it has aperiodically produce a "slide whistle" sound. That is the best describition that my wife and I can think of. It varies on lenght. One or two notes to several notes.
The "whistle" sound normall goes low to high. The first time it happen by wife was driving and almost panic. It continued on and off for over 30 miles and then just stoped. She drove stright to the car dealer. They checked the car out and could not find anything.
We have been keeping a log. It happens right after the car starts, after it been driven for a while, as we stop, as we start up from a stop, in rain, hot temp, cold temp. The car could "whistle" at least once a week or stop for 4 or 5 weeks.

Has anyone else heard a sound like this?

George M

The IMA system does seem to emit a sort of high-pitch whine that some people have heard, others don't. It changed tone depending on whether it was charging or assisting. I never did hear it until fairly recently, but hear it occasinally now.

It's most audible at lower speed or even stopped (while the engine is not in autostop) with the radio and fan down or off. I don't know if the noise cancellation system is a little out of kilter, or not designed to handle that high frequency.

Could your noise also be wind around a gasket? Or do you also hear it while stopped?

Heard the high whistle sound and considered many possibilities. Finally discovered that the windows were not completely closed and have not heard since.

First of all, congratulations, you have an excellent hearing.

Secondly, this noise is caused by the power inverter. The inverter operates at high frequency, and many of its components are made of materials that suffer from magnetostriction...they buzz.

You may have also heard high frequency magnetostriction if you get close to the back of your color TV (tube type, not LCD or plasma), because its deflection circuitry also oscillates at high frequency.

These frequencies are at the upper fringes of normal human hearing, so although it may be annoying, it means that you have got an excellent ear.

I know all this because this happens to me all the time. My HCH's IMA converter also whistles.

This is not a high frequency sound but a shrill whistle with two notes that feels like it is in the cabin.

Could your noise also be wind around a gasket? Or do you also hear it while stopped?[/quote]

The sound is quit audible. Anyone riding in the car can hear it.
We have heard it at "Highway speed". Stopped with or without the "auto stop".

George M

You do describe it well. The sound goes the up musical scale or sometime down. It can be long "slide" or very very short.

George M

The sound is quit audible. Anyone riding in the car can hear it.
We have heard it at "Highway speed". Stopped with or without the "auto stop".

George M[/quote]

Since you hear it with the vehicle stopped and the engine off, I agree that its likely magnetostriction from the IMA as it converts 144v to 12v for your cabin loads(IMA never truly inverts DC to the motor itself- it time-delays full DC voltage application at the motor poles themselves, which is effectively still an inverter but incurs no DC-AC conversion loss)

Now 'magnetostriction' is a funny sounding word, and Joe the service tech may think you're getting all science fiction-like on him if you throw that word out there. A good electronics tech, though, will know what you mean (you can look it up on wikipedia for details). Failing that, you'll need to record the sound or get the tech to ride with youand hear it himself.

As for what would fix it, that's hard to tell, especially if its present on all HAHs/part of the design and they simply assumed the frequency was out of audible range. But a good tech will still be able to pinpoint its source and maybe be able to attenuate it so you can't hear it.

good luck!

crazy idea... fan or a/c on or off? could be a whistle in the air ducts somewhere?

+af
Northwest Raleigh, NC, USA
'04 Silver opt.BC/9; 24,000+ miles so far
http://www.plusaf.com/prius/prius.htm
http://www.plusaf.com/coast/coast1.htm
My Prius without the trailer:

My Prius with the trailer:

yes. with fan on and fan off, with a/c on and a/c off

George m