AN RJ65 FLC CROSSES THEIR ASSIGNED FIX 1000 FT BELOW THEIR ASSIGNED ALT AT BUF; NY.

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ON FLT FROM CVG-ROC; CLRED TO CROSS BUF AT 11000 FT. ZOB THEN REQUESTED A LEVELOFF AT 12000 FT; AND A L TURN TO 360 DEGS. I AM QUITE SURE 12000 FT HAD BEEN SET IN THE ALT ALERTER. AFTER A FEW MI WE WERE CLRED DIRECT TO BUF AND THIS CREW BELIEVED WE WERE RECLRED TO 11000 FT. ON XING BUF AT 11000 FT CTR QUESTIONED OUR ALT; INFERRING OUR LAST CLRNC TO BE 12000 FT. A NUMBER OF FACTORS CAUSED ME TO BE UNSURE IF (ON SEEING 11000 FT IN THE ALT ALERTER) I HAD IN FACT CONFIRMED IT WHEN SET BY A VERY NEW FO. A POOR NIGHT'S SLEEP AFTER A PARTICULARLY HARD TRIP; THE DISTR OF LOOKING AT NIAGARA FALLS; AND DUE TO PROX TO BUF; THE NEED TO SPEND MORE TIME THAN NORMAL IN PROGRAMMING THE FMS. IT REQUIRED REPEATED INPUTS TO DEVELOP APPROPRIATE STEERING COMMANDS TO THE VOR. ONLY A READING OF THE ATC TAPES WILL CLARIFY IF CTR HAD; IN FACT; RECLRED US TO THE LOWER ALT. SUPPLEMENTAL INFO FROM ACN 481870: 2 MINS PRIOR TO THE VOR; WE WERE INSTRUCTED TO TURN L TO A NEW VECTOR AND MAINTAIN 12000 FT AND A 360 DEG HDG. BEFORE WE HAD LEVELED OFF FROM THE TURN; WE WERE CLRED BACK DIRECT BUF. I BELIEVE THE MAIN FACTOR OF THIS INCIDENT WAS THE RAPID FIRE OF NEW HEADINGS AND ALTS IN A SHORT TIME FRAME. WHETHER THE CLRNC WAS MISHEARD OF MISSPOKEN; IT WAS BEING XMITTED AT TOO FAST A RATE AND IT CREATED CONFUSION.