Investigators analysing the communications from the crew of the crashed Polish state Tupolev Tu-154 are trying to clean intrusive noise on recordings of the accident.
Polish specialists are being assigned the task of identifying the voices of the crew members.
"Voice information is very noisy and there are many sections that need restoration," says the Russian Interstate Aviation Committee (MAK).
The aircraft was destroyed as it struck trees while attempting an approach to Smolesnk, in dense fog, on 10 April.
Investigators have been working to determine the precise trajectory of the aircraft. The crash site is substantially to the left of the approach centreline to the runway marked 26 at the military airport.
MAK also states that it is analysing data from checks on the airport's navigation aids.