What will be the role of acoustic enclosure and muffler to reduce the noise of air compressor?

For L-type fixed reciprocating air compressor of 10, 20, 40m3/min, when muffler is not used at the air intake, the noise radiated from the air intake accounts for the major part of the noise of the whole machine. After installing appropriate muffler at the air inlet, the noise of the whole machine can generally be reduced to 90dBA, or even below 85dBA (1m distance). If the noise is further reduced, it is necessary to cover the sound insulation cover on the air compressor to obtain a substantial reduction in the noise of the whole machine. For 10, 20 m 3 / min screw air compressor, in the current situation, only the use of acoustic enclosure with intake and exhaust muffler, there is hope that the group noise will be reduced to below 85dBA.