Date: 202104
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Landing; Taxi
ATC / advisory: Tower ZZZ
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Time Pressure; Confusion; Workload; Troubleshooting; Communication Breakdown
Second reporter function: Pilot Not Flying; First Officer
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Clearance; Ground Incursion Taxiway
Detector: Person Air Traffic Control
When detected: Taxi
Result: Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance
Contributing factors: Procedure; Environment - Non Weather Related; Human Factors
Primary problem: Human Factors

Narrative: As the CA; I was the PF landing via RNAV Y Runway XXL at ZZZ. The approach was uneventful; and the landing was well within the touchdown zone. During landing rollout; after stowing the thrust reversers and slowing to exit the runway; I started to make the left turn to exit onto Taxiway 1. At that time; Tower came on the radio and said; 'Aircraft X; exit the highspeed [Taxiway] 2X or the reverse.' We understood the reverse to be Taxiway 1. My First Officer than switched to Ground; who told us to 'Taxi to the gate via Taxiway 2 and 3; cross [Runway] YYL; C and [Taxiway] 4;' to which my First Officer acknowledged.Ground Control then came on shortly thereafter with us on Taxiway 2 and told us that he really needed us on Taxiway 2X to exit; 'not' the reverse. We then realized that with everything going on in the cockpit during a typical ZZZ landing; stopping the aircraft; etc.; Tower probably told us to 'Exit the high speed [Taxiway] 2X; not the reverse.' Instead; we heard that to be 'Exit the high speed [Taxiway] 2X or the reverse.' The speed of the speech to which the clearance was given by the Tower also made the clearance difficult to understand; plus the radio sounded a bit muffled (Tower controllers wear masks while working). To note; there were no conflicts and no aircraft on Taxiway 2 upon exiting.After taxiing into the gate; I called the Tower directly and spoke with one of the controllers (but not the one who gave us that clearance). After explaining what I felt we heard the clearance to be; he responded that since they wear masks in the Tower; sometimes it's difficult to discern exact language with short bursts of words and hence the confusion between words like 'or' and 'not' when used in a quick clearance as was done in this situation. He said that most likely Tower was trying to get us off more quickly by using the high speed [Taxiway] 2X (instead of the reverse at Taxiway 1) in order to get a departing aircraft off before the next arrival.He told us 'no problem' and 'I'm sure the Tower Controller was not upset at all because I haven't heard about it.' So; most likely; it was simply a sequencing issue with Tower in order to expedite their flow. If the Controller had anticipated what he wanted and told us that clearance on final rather on during the last part of the landing roll after I positioned the aircraft into a left turn off onto Taxiway 1; that might have helped him. I also believe the mask that the Controller was wearing and the speed of his speech in which he delivered his clearance muffled the word 'not' that we heard as 'or.'


Second narrative: We landed [Runway] XXL at ZZZ and upon exiting XXL pointed towards Taxiway 1 (the reverse of the high speed); we were told 'Exit XXL on [Taxiway] 2X the high speed and NOT [Taxiway] 1.' We both heard it as 'Exit XXL on [Taxiway] 2X the high speed OR [Taxiway] 1.' Since we were already positioned to take [Taxiway 1]; we had an expectation bias and continued. I also didn't make it clear on the read back that I understood.  I saw Taxiway 2 and read back 'Exit at [Taxiway 2]' or something to that effect. On Ground frequency; we were alerted to our error.  The Captain followed up via phone call and it was suggested by Tower that perhaps their instructions were garbled by their use of a mask while working.


Synopsis: Air carrier flight crew reported a taxiway incursion and cited communication problems with ATC as a contributing factor.  Reportedly; the Controller's instructions sounded muffled due to wearing a face mask.