Light Transport
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 4.5
Communication Breakdown; Confusion; Distraction
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Provided Assistance; Flight Crew Returned To Clearance
Human Factors
Aircraft X was given a descent to FL330. After switching the aircraft to sector XY I observed the datablock display altitudes below 330. Upon calling the Controller; they stated that they were unsure of what the aircraft was doing. Subsequently; I called sector YY that had previously approved a point out on the aircraft and received approval for control for lower. I believe the pilot gave me a good readback.I am unsure of whether I was wearing a mask at the time or not as activity in the area fluctuates; and social distancing cannot be maintained; my mask comes and goes. It is plausible that I was wearing a mask at the time.  Despite; what I felt was a good readback; I could foresee my words being muffled due to wearing a mask. Therefore; it is possible that a pilot could mishear what I said.
Center Controller reported an altitude excursion and referenced wearing a mask may have muffled the transmission.