MTR ALT DEVIATION OVERSHOT CRUISE ALT.

Narrative

WHILE IN THE RIGHT SEAT; ACTING AS COPLT; HANDLING THE RADIO COMS; I DISCOVERED THAT MYSELF AND THE PLT AT THE CTLS WERE LACKING SOME INFO NEEDED AT OUR DEST. I PROCEEDED TO CONTACT COMPANY ACFT ON A UHF FREQ WHILE THE PLT AT THE CONTROLS CONTINUED TO MONITOR VHF FREQ; TALKING TO ZDC. I HAD DIFFICULTY HEARING COMPANY ACFT AND THEREFORE WAS CONCENTRATING ON MY CONVERSATION WITH THAT ACFT; ALONG WITH WRITING THE INFO DOWN. CENTER HAD CLRED US TO CLB TO FL230 (WE HAD FILED FOR FINAL ALT OF FL240). PLT AT THE CONTROLS THOUGHT WE HAD BEEN CLRED TO FL240. AT APPROX FL235 CENTER CONTACTED PLT AT THE CONTROLS AND INQUIRED ACFT ALT. WHEN PLT AT THE CONTROLS WAS INFORMED THAT WE HAD ONLY BEEN CLRED TO FL230 HE IMMEDIATELY DSNDED DOWN TO FL230. LACK OF COM; AND DISTR WERE THE CAUSES FOR THIS EVENT. I ALLOWED MY ATTN TO BE CONCENTRATED ON ONE SINGLE TASK (COPYING INFO FROM OTHER ACFT). THE NECESSARY CORRECTIVE ACTION TO PREVENT SUCH AN EVENT FROM OCCURRING AGAIN IS TWOFOLD: FIRST; MAKE CERTAIN THAT ALL FLT CREWMEMBERS ARE AWARE OF ALL CLRNCS. SECONDLY; DON'T LET ONE PROB CAUSE YOU TO BE DISTRACTED. I HAVE CERTAINLY LEARNED THESE LESSONS THROUGH THIS EVENT.