Hello @nuria!
That is very interesting- since the drum sounds seem to be calling specifically to you and are happening around the time you are practicing magick, I’d say they are worth looking into 
Dream Lookup (a site to find the symbolic meaning of things- usually presented through dreams) associates the following with the sound of a drum:
“Dreaming of a muffled thumping sound produced by a drum, is an indication of being called for help. This type of dream refers to a close friend or family member, who may currently be far from you physically, being in dire need of your assistance or support. While you may receive news or updates from this person in the near future, it may also be wise to consider reaching out to those around you and offer your aid if necessary.”
[From Dream Lookup]
There are many ways to read/interpret something (and many Books of Correspondences offering different ways to interpret!). I personally believe the best way to reveal the meaning of something is to examine not just the object, but also at the person’s experience.
Since you mentioned that the drum sounds come after Good Luck spells and that they leave you feeling relaxed and at peace- I’m more inclined to think they carry a different and more positive kind of message.
It is likely that, as Megan and Kasie pointed out, a higher power or deity may be trying to reach out to you. Meditations, being open and aware of other possible signs, and possibly reaching out to a deity of your choice may be good ways to discover what the sound of drums is directing you towards 
Good luck and blessed be! 