Need suggestions on how to reduce the noise levels of a borewell compressor


My neighbour has installed an air compressor for his borewell. It is placed at the edge of his building and is near the main door of my house. For the past 7-8 years, this has been the situation. Passages run through the sides of both houses and it is extremely difficult to bear the noise of the motor (compressor). Requests to do something about it has yielded no result. He says "Nothing can be done" to reduce the sound.

I suggested that  he could- a) Mount the compressor underneath the ground and provide a metallic access door to it on top or b) Cover the existing compressor on all 4 sides and underneath, with a thick wooden board. I feel both can reduce the noise to some extent. He says that these things "cannot be done".

Can anyone in this forum please suggest if there are any means of reducing the noise levels of the compressor?