i'd start going for walks when it occurs. not only will you be healthier, but you'll get an idea of the acoustics of the neighborhood, and begin to learn where it's coming from. and, you can also figure out at what times it occurs. within time, you'll figure out where it's coming from, what time it occurs, and then be able to pinpoint it.

sound is a strange thing; depending on the sound, and its wavelength, it might appear to be coming from different areas than it really is. get out and try to see where it's coming from. it could be very interesting to all of us.

Do you have any of those big metal electric transmission line towers in your area? I don't know why, but sometimes they make a sound just as you described.

Might be somebody's wind chimes. My neighbor has one that does this.

Could it be the sound of a forklift (or some mechical equipment) backing up? They make such a sound. At night with less traffic the sound probably carries much further.

There is a train that is several miles away from us and I only hear the whistle very late at night (2am) though trains go through all day.

.. perhaps it is like the traffic signal aid for the blind, but on one of the pieces of construction equipment, sometimes the barricades include that kind of tone?

Tim

My first thought was a flagpole. The rope and hook will ping when the wind blows.

But I'd make up something more exciting than that just so I could wear a foil hat.

Did you ever find out what the noise was?

I found out!!

I was working in the evening in the general area where I felt the sound was coming from and I heard it coming from an ice-cream truck!

It's a little truck that just stayed in that neighborhood and had a speaker pinging that sound from time to time.

Foil hat off.