B767 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 210; Flight Crew Type 3092
Aircraft Equipment Problem Less Severe
Flight Crew Landed in Emergency Condition; Flight Crew Diverted
Aircraft
At 37;000 ft in cruise for probably almost an hour all of the sudden got a very loud horn or siren sound on the flight deck. This sound was so loud it made flight deck communications and external communications very difficult. Captain tried to contact dispatch and maintenance while I flew the airplane and handled the radios. Communication with dispatch and FAs was difficult and was compounded by my flying and having a hard time talking to ATC. We landed at the airport we felt was most suitable at the time. We were unable to get enroute weather from dispatch or ATC. Later we encountered turbulence with the seatbelt sign on.
Reporter stated he never heard the precise cause; but the sound was not from a system alarm or horn and was most likely related to a pneumatic system ducting issue of some kind.
B767 First Officer reported diverting to an alternate airport after a very loud noise developed in the cockpit possibly related to a pneumatic duct leak that interfered with communications.