As I play the mandolin I don't have or need a mute, when the rest of you go looking for a mute I can just play forte instead of as loud as I can.

Mutes do as you suspected absorbe the sound, but it is more complex then that. You have always heard philosphers wonder "If a tree falls in a forest and nobody is there does it make a noise?" Well, as a country boy who used to heat with wood I studyied that, and have conclued that you are right, fire does release it. Those sputters you heard was all the pent up music, and the pop (which you may have noticed was much bigger) was the release of the sound from all the trees that fell in the forest during that tree's lifetime when noone was around to hear it. Promiss you won't tell anyone, because if the philosphers figgure it out they will have to work on a new problems which (as a philospher who knows) I can assure you is far more maddening.