It sounds like the amplifier has gone out. But to be sure lets unplug it to see if the noise stops. Here is the radio wiring diagrams so you can see how the radio works and the location of the Bose speaker amplifier. Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.
Images (Click to enlarge)
Monday, March 18th, 2019 AT 2:24 PM