Help me diagnose an unusual sound from my Mirage?

[cookiemonster]

I was driving yesterday and noticed a high pitched sound from - I'm guessing - the engine area (near my front left/driver's side). The sound only happens when the car is moving at about 5 to 9mph, with my foot off the accelerator. With the accelerator pressed down in that speed range, I don't hear the sound. Pressing the brakes doesn't get rid of the sound.

I've attached a spectral analysis of the sound I managed to record on my phone - it seems the sound is around 4345 Hertz. I've also attached a zip file of the sound I captured (in aac format).

Any ideas what this sound might point to would be appreciated!

[AtomicPunk]

Sounds like brake wear indicator to me. Or a loose shim maybe. Have you taken left front wheel off and looked around? I've seen debris stuck between pad/caliper housing and the rotor make noise before.