[villagetinker]

You might also be hearing noise conducted through the ground. You seem to be on good terms with your neighbor, so I would ask them to see if it would be possible to have noise/vibration pads installed at the pump. I would also contact a pool supply company (like pinch a penny) and ask if they know of a pump enclosure to cut down on noise. I would then offer to buy one for the neighbor. You contact a window supplier and ask them about the possible installation of a storm window outside the existing window to cutdown on the noise. I had a neighbor that was really into having a very quiet room to listen to music. He found sound absorbing panels which he placed on the walls which were very effective in making the room very quiet.