YouTube filmmaker Cory “Mr. Safety” Williams, aka DudeLikeHELLA, was wandering around Alaska with his girlfriend recently, when he decided to skip some rocks on a frozen lake in Anchorage.

What he didn’t expect, however, was the wonderfully bizarre sounds the skipping rocks made when they struck the lake’s surface. “This is the coolest sound I've ever heard!” he declared in a clip of the action.

The vlogger’s enthusiasm and sense of wonder is truly infectious. (Watch Williams' rock-skipping in the video above, which has been queued to start at 3:41.)

“Had to watch the rock skipping like 4 times. Such an amazing sound,” wrote one Facebook user Monday after watching Williams’ clip of his lakeside adventure.

“That sound was awesome but your reaction was … priceless!” quipped another.

Canadian magazine Cottage Life notes the “chirping and pinging” sounds made when rocks are thrown onto bodies of frozen water are caused by the vibration of the ice.

“They’re different from the noises you’d generate by whipping rocks at, say, dirt, because underneath the ice the water isn’t solid,” the magazine writes. “Ice vibrates up and down, similar to a drumhead or cymbal vibrating after being struck.”