Also check the seal on the doors of attached garages. Also, make sure you have tight fitting covers on your trash bins. I wouldn't depend on sonic devices alone to get rid of the mice that are still in the house. Traps and poison pellets will do the job. The only problem with poison is that the mice may die before they can leave the house.
Most farmers have one or more cats.
A cat really does help keep the mice population down. All rights reserved.