Narrative:

Crew departed normally; climbed to cruising altitude and leveled off. Approximately 6-7 minutes into cruise; a sudden humming noise was heard from an unknown location. It grew gradually into a loud whistling sound with vibration. Crew was unable to determine source of sound. Lead flight attendant called shortly after inquiring about the noise. Flight attendant informed [the] crew noise was coming from L1 boarding door. Crew cross-checked status pages and pressurization. All indications were green and normal. No EICAS msgs were presented and crew communication was established.crew requested descent from ATC to lower altitude. Center assigned 10K ft. Captain called for the donning of cockpit oxygen masks. Crew assigned pilot flying to first officer. Captain attempted to communicate with flight attendants to investigate noise. Sound was too loud for flight attendant (flight attendant) to hear crew. Inquired ATC on nearest airport; ZZZ1; at 45 miles. Weather there was ¾ mile visibility and a ceiling of 900 broken. Crew determined that ZZZ was the nearest suitable airport and proceeded there. Requested and was given direct to the destination; ZZZ. Center provided priority handling for us. Crew notified dispatcher of priority handling and intentions. Dispatcher concurred with decision. Crew removed O2 masks at 10K and proceeded to destination. No limitations were exceeded. No far's were violated. Crew requested crash fire rescue equipment (crash fire rescue) equipment to be standing by. Aircraft taxied off runway under own power and rescue vehicles were told to stand down.

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Original NASA ASRS Text

Title: EMB-175 flight crew reported loud noise at the L1 door; requiring a diversion and a precautionary landing.

Narrative: Crew departed normally; climbed to cruising altitude and leveled off. Approximately 6-7 minutes into cruise; a sudden humming noise was heard from an unknown location. It grew gradually into a loud whistling sound with vibration. Crew was unable to determine source of sound. Lead Flight Attendant called shortly after inquiring about the noise. Flight Attendant informed [the] crew noise was coming from L1 boarding door. Crew cross-checked status pages and pressurization. All indications were green and normal. No EICAS MSGs were presented and crew communication was established.Crew requested descent from ATC to lower altitude. Center assigned 10K ft. Captain called for the donning of cockpit oxygen masks. Crew assigned Pilot Flying to First Officer. Captain attempted to communicate with flight attendants to investigate noise. Sound was too loud for FA (Flight Attendant) to hear crew. Inquired ATC on nearest airport; ZZZ1; at 45 miles. Weather there was ¾ mile visibility and a ceiling of 900 broken. Crew determined that ZZZ was the nearest suitable airport and proceeded there. Requested and was given direct to the destination; ZZZ. Center provided priority handling for us. Crew notified Dispatcher of priority handling and intentions. Dispatcher concurred with decision. Crew removed O2 masks at 10K and proceeded to destination. No limitations were exceeded. No FAR's were violated. Crew requested CFR (Crash Fire Rescue) equipment to be standing by. Aircraft taxied off runway under own power and rescue vehicles were told to stand down.

Data retrieved from NASA's ASRS site 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.