A captain and first officer report a very loud squeal sound and vibration could be heard and felt th...

Narrative:

Got to the gate in ZZZ and noted maintenance was working on aircraft. They were getting ready to perform a ground pressurization test and asked us to remain at the top of the jet bridge while they performed their test. The test was due to a previous write-up for pressurization leak. Maintenance completed their test and signed-off the logbook along with our ETOPS sign-off. We then loaded the aircraft and proceeded on our leg from ZZZ to ZZZ1. On climb out above 17;000 ft we started to get a really loud air leak sound and could not determine where it was coming from; but it was very pronounced. We discussed the fact that this airplane had just had the pressurization check performed back on the ground in ZZZ to try to find the leak and the fact that the leak still existed even though all indications for cabin pressurization was normal. We also discussed whether it was prudent to continue the flight. Captain talked to the flight attendants in back [of cabin] multiple times to find out what 'they' were also hearing and feeling [and if] what sounded like a possible pressurization leak and also eventually a vibration coming from somewhere on the left side of the aircraft. After talking to maintenance; dispatch and the flight attendants in the back of the aircraft and based on the noise that we could hear and the vibration that we could feel; we agreed that the best course of action was to not continue this ETOPS flight and to return to ZZZ as soon as possible; therefore an emergency was declared and we came back to ZZZ and performed an uneventful overweight landing. After returning to ZZZ; we switched to a different aircraft; re-boarded and then departed to ZZZ1. Climb and cruise within first 30 minutes of flight. Use of captain's emergency authority [and] priority handling from ATC.

Original NASA ASRS Text

Title: A Captain and First Officer report a very loud squeal sound and vibration could be heard and felt throughout the cabin as their B737-800 ETOPS aircraft climbed through 17;000 FT. Emergency declared and aircraft returned to departure airport. Cabin pressurization had remained normal.

Narrative: Got to the gate in ZZZ and noted Maintenance was working on aircraft. They were getting ready to perform a Ground Pressurization Test and asked us to remain at the top of the jet bridge while they performed their test. The test was due to a previous write-up for pressurization leak. Maintenance completed their test and signed-off the logbook along with our ETOPS sign-off. We then loaded the aircraft and proceeded on our leg from ZZZ to ZZZ1. On climb out above 17;000 FT we started to get a really loud air leak sound and could not determine where it was coming from; but it was very pronounced. We discussed the fact that this airplane had just had the pressurization check performed back on the ground in ZZZ to try to find the leak and the fact that the leak still existed even though all indications for cabin pressurization was normal. We also discussed whether it was prudent to continue the flight. Captain talked to the flight attendants in back [of cabin] multiple times to find out what 'they' were also hearing and feeling [and if] what sounded like a possible pressurization leak and also eventually a vibration coming from somewhere on the left side of the aircraft. After talking to Maintenance; Dispatch and the Flight Attendants in the back of the aircraft and based on the noise that we could hear and the vibration that we could feel; we agreed that the best course of action was to not continue this ETOPS flight and to return to ZZZ as soon as possible; therefore an emergency was declared and we came back to ZZZ and performed an uneventful overweight landing. After returning to ZZZ; we switched to a different aircraft; re-boarded and then departed to ZZZ1. Climb and cruise within first 30 minutes of flight. Use of Captain's emergency authority [and] priority handling from ATC.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1133931
Time
Date	201312
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Pressurization System
Person 1
Function	Pilot Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 250 Flight Crew Total 15000 Flight Crew Type 9500
Person 2
Function	Pilot Not Flying Captain
Experience	Flight Crew Total 24000
Events
Anomaly	Aircraft Equipment Problem Critical Flight Deck / Cabin / Aircraft Event Other / Unknown

A captain and first officer report a very loud squeal sound and vibration could be heard and felt throughout the cabin as their B737-800 ETOPS aircraft climbed through 17;000 ft. Emergency declared and aircraft returned to departure airport. Cabin pressurization had remained normal.