E145 FLT CREW RETURNS TO DEP ARPT WHEN STATIC IN VHF COM AND THUNDERSTORMS MAKE IT IMPOSSIBLE TO CONTINUE TO DESTINATION.

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AFTER TAKING OFF ON RWY XXR; ABOUT 300-500 FT WE GOT LOUD STATIC IN BOTH THE CAPT'S HEADSET AND FO'S HEADSET. COULDN'T UNDERSTAND WHAT THE TWR WAS GIVING US. HAD TO ASK AGAIN AND TOLD HIM WE ARE HAVING STATIC IN OUR HEADSETS; HARD TO UNDERSTAND. I WAS TRYING TO FIND THE PROB SO WE CAN HEAR. WE FINALLY UNDERSTOOD TO SWITCH TO DEP BUT VERY HARD TO UNDERSTAND AT THAT POINT WITH DEP; AND NOT SURE IF WE GOT EVERYTHING FROM ATC. I SWITCH TO SPEAKER AT THAT TIME AND ASK AGAIN. I COULD HEAR THEM A LOT BETTER; BUT STILL HAD STATIC IN THE SPEAKER. AT LEAST WE COULD UNDERSTAND THEM. DURING THIS TIME; I MADE SURE THE OBSERVER'S HEADSET WASN'T PLUGGED IN AND CHANGED OUT HEADSETS. THEN ASKED THE FO TO CHANGE HEADSETS TO SEE IF THAT WOULD HELP. THAT DIDN'T WORK AT ALL AND WE WERE STILL GETTING STATIC. THE STATIC WOULD GO AWAY BUT COME BACK WITHIN 1 MIN OR LESS AS LOUD AS WHEN WE TOOK OFF. AT THAT POINT I CONTACTED MAINT CTL TO SEE IF THERE WAS SOMETHING WE COULD DO. THEY SAID THE ONLY WAY WE CAN FIX IT; IS IF WE CAME BACK. I MADE THE DECISION TO RETURN TO ZZZ BECAUSE WE COULDN'T COM BTWN EACH OTHER VERY WELL WITHOUT OUR HEADSET; AND IF GOING INTO ZZZ1 THAT HAD TSTM IN THE AREA UPON OUR ARR; JUST DIDN'T FEEL SAFE WITHOUT THEM. AT FL270 WE TOLD ATC THAT WE ARE HAVING HEADSET PROB; AND WOULD LIKE TO RETURN TO ZZZ. AT THAT POINT WE HAD TO BURN OFF FUEL FOR LNDG; SO WE WENT TO A HOLDING PATTERN. AFTER HOLDING IN 4 DIFFERENT PLACES DUE TO TSTMS AND AVOIDING THEM; WE WENT THROUGH ONE CLOUD THAT LOOKED FINE BUT WE GOT A STRONG SULFUR SMELL IN THE FLT DECK. WE DIDN'T SEE ANY FLASH OF LIGHTNING AND CONTINUED. FEW MINS LATER THE LIGHTS IN THE CABIN WENT OUT AND THE EMER LIGHTS CAME ON. THAT POINT FLT ATTENDANT CALLED AND ASKED WHAT WENT WRONG. HE TOLD US IT'S COMPLETELY DARK IN THE CABIN AND JUST THE EMER LIGHTS CAME ON. I CYCLED THE EMER LIGHTS AND TOOK ABOUT 15 SECONDS FOR THE MAIN CABIN LIGHTS TO COME BACK ON AND THE EMER LIGHTS TO GO OUT. I DECIDED AT THAT POINT I FELT THAT IF THE LIGHTS WENT OUT IN THE CABIN; I DIDN'T WANT TO TAKE THE CHANCE THAT WE COULD HAVE AN ELECTRICAL PROB UP IN THE FLT DECK; AND COULD HAVE A SAFETY ISSUE. SO I CONTACTED DISPATCH WITH THE PROB AND TOLD THEM WE ARE DECLARING AN EMER; WITH AN OVERWT LNDG. HE TOLD US OK AND LAND LESS THAN 360 FPM. I TOLD ATC ABOUT THE PROB AND DECLARED AN EMER. WE ASKED FOR LONGEST RWY AND HAVE THE FIRE TRUCKS THERE JUST IN CASE. WE GOT RWY XXR AND HAD NO FURTHER PROB UNTIL LNDG. WE GOT A VERY STRONG ELECTRICAL SMELL IN THE FLT DECK. WE DID HAVE THE FIRE TRUCK LOOK AROUND THE ACFT BEFORE RETURNING TO THE GATE. ALSO NOTING THAT WE DON'T KNOW IF WE MISSED ANY CALLS FROM ATC WITH OUR PROB; BUT DID HAVE AT ONE TIME THAT WE LEVELED OFF AND ATC TOLD US WE WERE CLRED UP TO AN ALT. AFTER TALKING TO THE MAINT GENTLEMAN; HE TOLD US IT COULD HAVE BEEN A PROB WITH THE OUTSIDE JACK; AND SOMETHING STUCK IN IT TO CAUSE THIS PROB.