I could hear the pit-a-pats of their little feet as they ran down the hallway.

The rain pit-a-pats on the roof.

I could hear the rain pit-a-pat on the roof.

I could hear the pit-a-pat of raindrops on the roof.

She could hear her heart pit-a-pat with excitement.

The rain pit-a-patted on the roof.

I could hear the rain pit-a-patting on the roof.