Well, if you have a pump that is submirsible and you have it in the sump and it is just laying on the bottom of the sump, you are having vibrating plastic against the acrylic, that is of course going to be loud and noisy...If you found a piece of rubber, that would not leach anything into the water and set that under it, it might cut down on it alot...also if you put some foam under the sump, that might help and then lined the stand with foam you might yield some really good results, the foam is not that expensive and worth it, before you start buying a new pump or cutting holes in your wall...