Garage slab reverberates

On an inspection today I noticed that the garage slab was giving off a noticeable reverberation when stomping in the center. This did not occur anywhere less than about 4 feet from the perimeter of the whole garage. I’m wondering how concerned I should be about this.

Let me answer that with a question…
Can you think of any conditions that would cause the scenario you mention?

List them all here:
1)
2)
3)
4)

Now look back at your list.

You have your answer.

I knew you had it in you!