default timer sound

Howdy folks,

Does anyone know how to change the default sound that is played when the TIMER goes off? By timer i do not mean alarm, notifications or anything else. When you ask siri "set timer for ten minutes," I am talking about the sound that is played in ten minutes from that time. I know you can set the sound of your preference for that one timer but when doing so, among the sounds listed to choose from, one of the sounds listed (in my case the "radar" sound) says "(default)" next to it. How do I pick which sound is this default? Any help would be very much appreciated! Thanks!