I've had my ONE XLS for about a year and a half and recently purchased the 4 map update package and downloaded an update? (you don't really know do you/). The next time I went on I-19 to Tucson, I heard this loud (I can only describe it like an electronic "Big Ben' chime) noise when nearing an off ramp. I nearly jumped out of my skin. I wasn't for sure it was eve coming from the XLS until I turned off the radio and waited for it to happen again- it did and it was!\n\nI have been well off the interstate in the mountains of AZ and CO and had almost forgotten about the sound and what causes it. Earlier this week, I downloaded another update? Today we were drving north on US 50 in CO between Salida and Canon City and out of a clear blue sky got the tone again when nearing and leaving a couple of small towns along the Arkansas River. I could not idetify any specific circumstances other than being in the small towns.\n\nIs any one else hearing these noises? I do not have traffic, Blue tooth or anything fancy that I am aware of.\n\nI hate mysteries.\n\nTerry L.