Date: 201501
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Night
Aircraft: Regional Jet 700 ER/LR (CRJ700)
Operator: Air Carrier
Operating under: Part 91
Flight plan: IFR
Mission: Ferry / Re-Positioning
Flight phase: Climb
Airspace: Class E ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Exterior Pax/Crew Door
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Distraction; Troubleshooting; Confusion
Second reporter function: Pilot Not Flying; First Officer
Anomaly: ATC Issue All Types; Aircraft Equipment Problem Less Severe
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action; General Declared Emergency; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: We departed on a part 91 repositioning flight for this aircraft after the plane had just completed a heavy check.  The plane was to be repositioned for the morning revenue flight. On departure; during the climb we began to hear a loud squealing/humming noise.  Sometimes we hear a noise momentarily as the seals set on the door during cabin pressurization.  This time; however; the noise was a little louder than normal and we began to discuss the issue.  On our contact with Center we requested to level at FL180 to troubleshoot the problem.  ATC continued our climb to FL180.  During climb at approximately 15;300; we got a loud howling noise and then a pop.  Captain (CA) immediately told center we needed to descend.  Center gave us pilot discretion to 11;000 and asked if we needed lower. We told him we would advise. CA donned O2 mask and First Officer (FO) followed.  We established communication between each other began a descent.  CA called for Emergency Descent Procedure.  We were quickly at a safe altitude where we could stow the masks.  We declared the Emergency with ATC due to possible structural failure and advised of a possible pressurization issue.  Cabin pressure did not appear to rapidly climb and no loss of pressurization was observed on EICAS after we reached a safe altitude.  We advised ATC we would need delay vectors to get set up for the approach.  We landed on the ILS in VFR conditions.  No emergency equipment was positioned ready upon arrival.  Clearing the runway; we advised ATC that we no longer required assistance.  ATC seemed to be caught off guard by that statement.  It appears that there was a breakdown of communication between the approach controller who received the Emergency advisory from ATC and the Tower Controller.  The aircraft arrived safely at the gate/ramp area.  The Maintenance write up was 'Loud hissing/squealing during climb.  Heard loud pop.  Performed emergency descent. Ran QRH.  Found hole in main cabin door seal.  Cabin did not lose pressure.'Upon arrival at the ramp/gate; Bombardier Maintenance met the aircraft.  Before we opened the main cabin door; no damage was visible; handle was stowed; and all pins were lined up green.  Upon opening the main cabin door; maintenance discovered a hole that had blown open in the main cabin door seal.  The hole was approximately the size of a quarter.


Second narrative: [Report narrative contained no additional information.]


Synopsis: A CRJ-700 developed a loud squeal during climb so the crew declared an emergency; conducted an emergency descent and after landing discovered the main cabin door seal developed a quarter size hole.