ALT BUST IN DSCNT.

Narrative

DSNDING INTO GLARE; I REACHED TO GET A PAPER OUT OF MY UNIFORM. AT THAT TIME; WE WERE GIVEN A DSCNT TO 6000 FT. I WAS FLYING; THE COPLT WAS RUNNING THE RADIOS. I DIDN'T HEAR THE ALT BECAUSE MY EAR PIECE SLIPPED OUT UPON LEANING BACK TO THE R TO GET THE PAPER. THE PROBLEM WAS THE COPLT SET 6000 FT IN THE ALT LEVEL OFF WHEN 7000 FT WAS GIVEN. I ASSUMED IT WAS 6000 FT SINCE THAT WAS SET. I CALLED 7000 FT FOR 6000 FT UPON PASSING 7000 FT. AT 6600 FT; ATC CALLED AND TOLD US OUR ALT WAS 7000 FT. AFTER THEY CALLED THE COPLT SAID HE WASN'T SURE IF HE SAID 6000 FT OR 7000 FT; BUT HE SET 6000 FT. EAR PIECES OFTEN FALL OUT OF OUR EARS; HOWEVER; THIS WAS A MOST INAPPROPRIATE TIME TO MISS A RADIO CALL; AND AN INAPPROPRIATE TIME FOR THE COPLT TO SET THE WRONG ALT. 2 SMALL PROBLEMS BECAME BIG ONES. IN SHORT: I DIDN'T HEAR THE ALT GIVEN; THE COPLT THOUGHT HE HEARD 6000 FT INSTEAD OF 7000 FT. THE INTERESTING PART IS THAT I WAS REACHING FOR A NASA RPT FORM WHEN THE ALT WAS GIVEN. SUPPLEMENTAL INFO FROM ACN 218574: IT WAS UNCLR WHETHER 6000 WAS ACTUALLY ASSIGNED OR WAS MISSET IN FLT GUIDANCE SYS. ALT SELECT KNOB IS SENSITIVE IN THAT TYPE OF SYS AND ALT SETTING CAN BE CHANGED WHEN SIMPLY RELEASING THE KNOB; OR IN PULLING THE KNOB TO ARM ALT.