Can I change the alert signal for calls in MarineCalls and RadioCalls?

The calls use an audio file that contains the actual call sound. The name and path of the call audio file is: C:\ProgramData\Mimer\radiocall.wav
You can replace this file with another file with exactly the same name but containing any other sound you want.
There are also other sound files in the same folder. Their names explains where they are used.