> Are you sure the sound is continuous
>
> If it's an occasional chirp, try looking for a smoke alarm
> with a low battery

About six months ago, my son found a long standing "fan noise".
For quite a while, I had heard a faint "cooling fan going bad"
noise coming from a collection of disk drives.  It was loudest
in the doorway but I was never able to track it to a specific
fan.  I thought I'd find it when it got worse.

Turns out my wife's exercise bicycle (between doorway & disks)
has an LCD module.  It makes a really faint bad fan noise -- for
a long time -- if the batteries are at mid-power levels.  Module
appears fine & works normally.  When the batteries do finally
start to fail, the module makes a normal "dead battery" loud
chirpy noise that's easy to find.

When we took the batteries out of the bike's LCD module, I found
that the faint bad fan noise was gone.

As someone else said, sometimes it just take persistence (& luck).

						Lee Jones

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