ACR FLC DISCOVERS MUSIC ON ALL COM CHANNELS WHEN ASKED TO CHANGE FREQ TO NEW CTR SECTOR. FLC SUSPECTED FM RADIO XMISSIONS FROM PAX CABIN.

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ENRTE FROM HOUSTON TO LAGUARDIA; FL330; RECEPTION ON CTR FREQ BECAME WEAK AND WE ASKED FOR A NEW FREQ. COULD BARELY UNDERSTAND THE NEW FREQ BUT DIALED IT IN AND TRIED TO CALL CTR. BEGAN TO HEAR MUSIC ON THAT FREQ AND SWITCHED TO OLD FREQ TO REQUEST A BETTER FREQ. LAST CTLR TOLD US TO TRY AGAIN THAT SAME FREQ (I THINK IT WAS 132.95) WHICH WE DID ON ANOTHER RADIO. HEARD SAME MUSIC ON COM 2. SWITCHED TO COM 3 AND STILL ONLY MUSIC ON THAT FREQ. I REALIZED THAT SOMETHING WAS CAUSING ALL OF OUR COMS TO RECEIVE MUSIC; BLOCKING ALL FREQS. I CALLED FLT ATTENDANTS AND ASK THEM TO CHK IN CABIN FOR ANYONE WHO MIGHT BE USING AN FM RADIO IN THE CABIN. THEY MADE A PA ASKING ANY PAX PLAYING AN FM RADIO TO TURN IT OFF. THE MUSIC INTERFERENCE STOPPED SEVERAL MOMENTS LATER. I HAD PREVIOUSLY THOUGHT FM RADIOS WOULD CAUSE ONLY NAV INTERFERENCE (IE; VOR NEEDLES POINTING ERRONEOUSLY) AND DIDN'T REALIZE THAT FM RECEPTION COULD BOUNCE AROUND; INSIDE THE ACFT AND BLOCK ALL OTHER VHF COM RECEPTION? I FEEL THIS IS A COMMON MISCONCEPTION THAT SHOULD BE DISSEMINATED TO THE AIRLINE PLT COMMUNITY WHO MIGHT ENCOUNTER THIS PROBLEM IN THE FUTURE. SEVERAL FELLOW PLTS TO WHOM I TOLD THIS STORY HAD NO IDEA THAT FM RADIO USAGE COULD CAUSE SUCH PROBLEMS AND BLOCK ALL INCOMING FREQS.