Date: 202103
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: Marginal
Light: Night
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class E ZZZ
ATC / advisory: TRACON ZZZ
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Human factors: Workload; Situational Awareness; Physiological - Other; Communication Breakdown; Distraction
Second reporter function: Captain; Pilot Not Flying
Anomaly: Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Became Reoriented; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Environment - Non Weather Related; Human Factors
Primary problem: Human Factors

Narrative: We conducted the ZZZZZ4 arrival and joined the ILS XX approach from ZZZZZ [Intersection] as briefed. When the Captain contacted the Tower; the Controller cleared us to land XX Right. The Captain read back the clearance. I said; 'Can you confirm Controller wants us to land on the right? We're on the ILS XX Left.' The Captain confirmed with the Controller cleared to land on the right. The Controller responded 'Affirmative. XX Right; Cleared to land.' At the time; we were well above 1;000 feet in visual conditions with the runway in sight and; so I had no objection. I clicked off the autopilot and side-stepped to XX Right and we landed. No issues arose with ATC or any other traffic. The next day; the Captain reached out to me and we spoke over the phone. Captain learned that we had actually been cleared for the ILS XX Right approach and Captain intended to file a report. A couple of days later I was finally able to confirm that this was correct. We aren't able to determine if it was being read back correctly or incorrectly; but there was never a clarification type of response from ZZZ Approach. It's also important to bring up that the Captain was wearing a face mask throughout the flight operations which did contribute to difficulties in communication with myself and with ATC at various times during the trip. This likely was a contributing factor to our deviation. Another contributing factor was the violation of sterile cockpit below 18;000 feet by the Captain and myself. Personally; I was distracted by our conversation as well as the fact that Captain was wearing a mask during the flight.Complacency is also a factor as the ZZZZZ4 Arrival usually results in the ILS or visual to XX Left.I think our company needs to take a harder stance on mask-wearing during flight operations in the flight deck.  I recommend that the company forbids the use of masks by pilots during flight operations to ensure that communications are clear and effective. In this case; it can be assumed that the Captain was repeating the clearance saying 'XX Left' but the Controller did not hear it clearly and assumed Captain was saying XX Right. Therefore; Captain was never corrected and we continued with what we had expected in our heads. There were multiple points throughout our trip that ATC did not understand the Captain and asked who was calling or needed clarification on what Captain was saying because it was difficult to understand with the mask. I thought on several occasions throughout our trip that it was the Captain's choice to wear it but if we have an emergency situation that I really hope Captain would take it off so that effective communication could be established and maintained. An emergency situation did not occur; but clearly an issue did arise with our approach to our destination.


Second narrative: ZZZ had a broken layer at 1;700 feet and we were expecting to do an approach. Descending into ZZZ on the ZZZZZ4 arrival we had set up for the ILS [Runway] XXL. We were assigned to join the ILS [Runway] XXR at ZZZZZ [Intersection] and then later cleared for the ILS XXR approach. We did not fly the ILS XXR. We flew the XXL approach and when we were on with Tower; we told them we were inbound on the ILS XXL. Tower cleared us to land XXR. By the time we contacted Tower we were out of the clouds and could see the runway. We verified two times that we were cleared to land XXR and not XXL. And Tower confirmed that we were to land XXR. Since we had visual on the runway; we side stepped and landed on XXR. We were probably at 1;500-1;600 feet AFE when we side stepped. We were confused as to why they had changed runways on us; but we knew that XXR was longer than XXL and that the landing speeds were the same and we were familiar with the airport. As we side stepped; I programmed in the ILS XXR so that we had a backup source even though we visually had the airport in sight. Later in the evening it still didn't sit right with me that we had a runway change that late; especially since we had been on an IFR approach. I realized we had in fact been assigned ILS XXR all the way back on with Approach. They never corrected me. So; I either read it back correctly but we were really hearing what we wanted to hear (ILS XXL) or they never corrected me and we all missed it. The approach was stable all the way through for XXL and the sidestep was done in a safe manner.I attribute not being sterile in the descent as a factor even though we were assigned to join ILS XXR at ZZZZZ prior to FL180. I would say complacency and expectancy were the primary factors. XXL wasn't closed and we were set that we would be doing the ILS XXL. It was also the last leg on the last day of our trip and we had had a long day. I had been up since 8 or 9am and we had flown 4 legs. This flight landed around XApm.I can say that I once again am reminded how serious our jobs are and that miss hearing a simple 'L' vs 'R' can be life changing. I can only say that I am thankful that this took place during a low traffic period and that we were able to maintain a safe condition. I'm honestly not too sure how to avoid this situation. I believe that writing down my clearances would assist in allowing me to verify and that maybe I need to make sure to turn my headset up so that I won't miss ATC.


Synopsis: Air Carrier flight crew reported a track heading deviation during approach due to communication issues with ATC.  The First Officer cited the Captain wearing a face mask on the flight deck may have contributed to the communication problems with ATC and between them.