Forget jingling bells and ho-ho-hos, these are now the sounds of the holidays.

The humming is constant; a low-pitched drone from 155 miles of conveyer belts racing packages in every direction. Boxes shift from one belt to another and bump into a metal wall. Thud. Thud. Thud. In the background, trucks beep and jet engines roar.

As more gift-givers shop online, there are more packages to ship. Online sales now account for 10 percent of all shopping and 15 percent during the holidays, according to research firm Forrester. That leaves FedEx and UPS with a combined 947 million packages to deliver between Black

Friday and Christmas Eve – up 8 percent from last holiday season’s forecasts.

For UPS, the key to getting all those last-second orders delivered on time is Worldport, a massive sorting facility located between the Louisville airport’s two main runways. On a typical night, 1.6 million packages pass through. Just before Christmas, there can be 4 million, peaking on Monday night.

– Associated Press