That sounds like normal high speed (3600 RPM) pump noise, amplified by direct contact with the slab. Unfortunately, standard 3600 RPM pumps ARE intrinsically noisy.

Unbolt it, and slip a door mat under it. I think you'll find that greatly reduces the noise.

But, if you really want it to be quiet, convert to a two speed pump, and run on low most of the time. Low speed, on most pumps, uses ~1/4 the electricity, but moves ~1/2 as much water . . . and is much, much quieter.