Jan, I've been living in Herculaneum for about 20 years (a small world, isn't it!?) and, alas, I have to tell the is mostly uneven to find barraks there... They would have been in the outmost part of town, if any, but all that part now is under the new town (Ercolano nowadays) and it would be really impossible to discover them
And, for the civilian drums in the frescos (wall paintings)... I'm only aware of what is called "tamburello" or "tammorra"! A very small instrument used to play "tarantella": would you like to have all those enemies laughing at your legions?

Hi Enrico i visited Napoli during a cruise. missed seeing Pompei and Herculaneum(tour operator did not go there) but saw Sulphatario instead(would rather have seen Herculaneum, but it was mayday and traffic around Napoli was jammed. Lovely country side.

Made up for it on next port in Livorno/Leghorn and saw Fireza/Florence and its Renaissance finese also managed to climb the Pisa Tower before it closed.