When we flush the toilets in the house there's a sound like a motor running in the pipes throughout the house. This just started... never heard it before yesterday. How can I figure out what it is?

You may have dirt or the seal unseated inside your ballcock, shut the water off under the tank and take the lid off the tank. Remove the three screws on top of the ballcock,(sae image) and pull the stem,washer and float assembly up. Pry the washer out and turn it over, put you hand on top of the open ballcock let some open shut off valve to flush dirt out of the ballcock, turn te seal over install and assemble the ballcock, see if it will fix your problem, if not come back and we will tell what will be the next step, Thanks.

John