Abstract: For the purpose of reducing the noise at the J - 50 timber - collecting tractor operator' s ears from 100 dB(A) to 90 dB(A) and below, at present the lowest international standard, the authors proved through investgation by modern measuring and analyzing technology of noises that the main sources of noises at the operator' s ears are the engine inlet valves noises and the surface radiation noises. By adopting comprehensive,simple and low cost measures such as moving the engine air filter out of the driver' s cab, attaching accoustic sound-insulating plastic plate on the left-side soft curtain of the engine and adding rubber pal on the cab floor, the authors achieved good results in the reduction of noises at the operator' s ears down to a level of 88-91 dB(A).