Weird beep coming from under the dash?

There's a weird beep coming from under my dash occasionally. For some of the 'older' folks in here, it sounds like a DOS error beep. (remember DOS? ) It sometimes happens frequently, sometimes only now and then, but it's annoying always because I don't know what it is.....

 

It doesn't matter if the truck is moving or not or even the wind speed outside.

 

@JC1971 it might be

 

It happens at all temperatures. In Waterloo, IA last week at -4° and in Texas today over 60°.

 

I could add that it is barely audible with the radio off. That is, with any more noise than what the truck itself generates I don't hear it.

 

Will need to check that, maybe. Volts with engine on are always 14.5, so...a possibility.