Not in a vehicle but NB does work

[KC1BAQ]

Do you think you can record it and attach it so we can hear?

If you have a portable am/fm radio, turn it on am and down near the lower end of the dial. Walk around your house and hold the radio next to different devices to see if you can locate it. You might also want to take it outside and see if it could be coming from one of your cars or perhaps one of your neighbors cars....or one parked on the street. Check all types of electronic charging devices, electric heaters, electric blankets, and your breaker box.

Keep us posted!

73,
Joe
KC1BAQ

I didn't know that site existed... my sound was like the electric fence but at about 2x the period.

Steve, have you looked at the ARRL "Sounds of RFI" page to see if you can find a match?

http://www.arrl.org/sounds-of-rfi

73,
Joe
KC1BAQ

Thought I'd post...
On 40M I heard a lot of noise, most likely QRM, .. shut my overhead dimmer to the shack (no help). It was a tick-tick-tick and about 100+hz. Very annoying. Not on other bands. Pressed the NB button and all went away. I'm new to this and thought that would be more for vehicle type noise (alternator/vehicle computer/etc.) but it worked for me. To the seasoned folks you probably already knew this, but I'm a "youngster" at this.