Does your Canon CP-E4 Battery Pack make a "buzzing" sound?

I have a new CP-E4 Canon Battery Pack attached to a 580EXII Speedlite and the Battery Pack is making a buzzing sound.

Has anyone else experienced this?

Is it normal, and should I be concerned?

I've tried it with regular AA batteries, and with NiMH rechargeable AA batteries, and it does the same thing.

Seems to function ok, it's just a noise that made me feel cautious to use the pack.

Anyone?

I've never heard a sound from mine. I'm not even sure what could make a buzz sound in the unit. Unless many people have had the same issue over a period of time with no failure, I'd guess there are some electronics in your unit getting ready to fail.

It all works fine, and the buzzing sound is very subtle. When you trigger the flash, if you put your ear up to the battery pack, it also makes a short, high-pitched whine sound to.

Very weird. I hope it's not failing, it's brand new!

The sound if probably the transformer during the charging cycle.
I have two CPE4s, they are shielded around the transformer an I don't notice the sound.
I also have two SF-18 HK knock offs. They are not shielded and do have the faint buzzing sound during the charge cycle. When the light says the speedlite is charged the buzzing stops.

Mine makes a slight buzzing sound, which seems to get worse as the batteries are almost drained.

Big G,
That would seem to reinforce the transformer hum as the source. As the batteries get weak they loose voltage which means the transformer is working harder too.