Date: 201307
Local time of day: 0601-1200
Location: ZZZ.ARTCC, US
Flight conditions: IMC
Weather elements / visibility: Thunderstorm; Turbulence
Light: Daylight
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Communication Systems
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Workload; Troubleshooting; Confusion; Communication Breakdown
Second reporter function: First Officer; Pilot Flying
Anomaly: Aircraft Equipment Problem Critical; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action; Flight Crew Diverted; Flight Crew Landed As Precaution; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: During cruise flight; we experienced multiple failures in the aircraft's communication system; resulting in a diversion. While in cruise at FL350; we began to navigate through an area of storms. We had asked the flight attendants to be seated; and they called us back to request a PA. We were also communicating with Dispatch via ACARS about routing through the weather. We were talking to ATC on COMM 1; and monitoring guard on COMM 2. All of this communication was normal. As we entered some of the weather; COMM 1 became scratchy; as we encountered some ice crystals at altitude. This is a fairly common issue; and we thought nothing of it. Shortly thereafter; communication between ATC and all aircraft on the frequency became impeded by an aircraft keying the mic every other second or so. About this time; we heard multiple chimes in the cabin; and heard one chime in the flight deck; indicated the flight attendants were trying to call is; but there was no indication of this on the Audio Control Panel. Thinking it was just a wrong button push; we were going to wait a few seconds; and call back to make sure all was well. It was then that we realized that the aircraft keying the mic on the Center frequency was us. We noticed the TX message in the COMM 1 box on the MCDU flash regularly. We checked every mic button; but the problem continued. We then switched to COMM 2; but noticed that COMM 1 was still transmitting; despite not being selected on any audio panel (Captain; First Officer; or observers); and was blocking ATC. I then switched the COMM 1 active frequency to 123.45 so that it would not interfere with ATC. At this point we considered COMM 1 useless. Before we had a chance to delve into that issue; we realized that the Emergency chime had been sounding in the cabin constantly since the issues began. We attempted to call the flight attendants; but had much difficulty reaching them using the intercom system. We would need to call them multiple times to get connected; and when we did connect; we were cut off after a few seconds by another cycle of the Emergency Chime. We looked to the QRH for guidance; but were unable to find anything for these failures. We decided to contact Dispatch. Wanting to expedite our communication I decided to call a Commercial Radio service for a relay. Since COMM 1 was useless; and COMM 2 was being used for ATC; I switched COMM 3 to voice mode. While I was able to establish communication; I was not able to hear our Dispatcher. I than relayed a message to Dispatch through a Commercial Radio service with the scope of our problem and a suggestion that we divert. I also briefly reactivated the ACARS to send the same information. With multiple failures with an unknown cause; I was worried that we might begin to lose more systems. I was also concerned that I was unable to effectively communicate with the flight attendants; and that passengers would begin to become alarmed by the constant; loud chiming. I was also confident that this was not a problem that would be easily fixed while airborne; so when Maintenance sent us an ACARS suggesting we troubleshoot; and that we were allowed to continue; I declined; preferring to divert. (I don't believe Dispatch understood the full scope of the issues at this point). We communicated our request with ATC; and stated several times that this was not an emergency; and that we required no assistance beyond clearance to the divert airport. At one point; ATC asked us if our flight deck door was secure; we told them it was; and reiterated that this was simply a precautionary landing; not an emergency. We told the flight attendants as best we could about the diversion. I attempted to make a PA; but only heard squelch; and was told later that the cabin heard nothing but squelch as well. We learned later that the flight attendants PA system was also not working; so they used the megaphones to prepare the cabin for arrival. We then landed normally; and taxied to a gate. Duringthe final descent; I noticed that COMM 1 was now showing a stuck mic indication despite still not being selected by any audio control panel (ACP). After we opened the flight deck door; we were informed that for the last 5-10 minutes of the flight; ALL flight deck communication was transmitted over the cabin PA system; including ATC communication and our hot mic conversation. While all of our communication was about the operation of the aircraft; and the current situation; we did unfortunately use some vulgar language during this was time; that was; completely unbeknownst to us; heard by the passengers in the cabin. After apologizing profusely for the situation; and the language; we deplaned the passengers. (It was warm; and the Mechanic was at least 20 minutes away; with an unknown prognosis on the aircraft.) After talking with the flight attendants; we learned that their PA system was totally unusable; and all attempts to talk to us were either unsuccessful; or met with a loud squelch tone. We also learned that the cabin light bar was flashing randomly; and not matching the Emergency or normal chimes. After Maintenance reset the issue; we boarded up; but had to wait 20 minutes after the jet bridge was pulled for anyone on the ramp to bother coming over to push us back. We then continued to our filed destination uneventfully.


Second narrative: [Narrative #2 contains no additional information.]


Synopsis: An ERJ-170 crew diverted after the aircraft's entire communications system malfunctioned resulting in a stuck VHF radio with no selection on any communication panel and a continual cabin emergency chime along with flight deck communications on the PA.