Regional Jet 200 ER/LR (CRJ200)
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Communication Breakdown; Situational Awareness
ATC Issue All Types; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Human Factors
After checking in with Approach; I heard and read back cleared to descend to 2;000 [feet]. The Pilot Flying also heard 2;000 [feet] and set 2;000 [feet] in the ALT Alerter. Passing through approximately 5;500 feet; ATC said your assigned altitude is 6;000 [feet]. After the Pilot Flying was slow to react; I disengaged the autopilot and leveled the aircraft at 5;000 [feet] and started to climb back to 6;000 [feet]. ATC then assigned 5;000 [feet] and gave us vectors.Both pilots hearing the wrong altitude; or the Controller [made a] mistake of giving the wrong altitude. Passing through approximately 10;000 [feet]; I thought that 2;000 feet sounded a little low for our area. But I dismissed it because I was sure I heard it. Also 2;000 feet is usually the altitude given for the visual approach; so in that sense it sounded normal. At my first second thought; I should have asked the Controller for the altitude again.
The Captain [and I] heard an instruction from Approach to descend and maintain 2;000 feet upon checking in ~40 miles north on descent. I believe the Captain read back the 2;000 feet altitude instruction. The Captain and I followed the appropriate callout per the SOP after selecting 2;000 feet in the Alt Preselect. Reaching 5;400 [feet]; the Approach Controller informed us our assigned altitude was 6;000 [feet]; but that his MVA was 5;000 [feet]. He then proceeded to say everything was good and instructed us to fly a heading of 150 and maintain 5;000 [feet]. He then vectored us for a visual approach without further incident. Following the event; the crew reviewed and confirmed we both heard an instructed descent to 2;000 [feet]; which was verified and selected in the Alt Preselect. Next time; question a descent all the way down to 2;000 [feet] when in the mid-teens altitude wise with some terrain east of the airport.
CRJ-200 flight crew reported descending below cleared altitude on arrival after apparently misunderstanding the Approach Controller.