Search and rescue was something that Gibbs had experience with, but most of his experience with it had been either in the military or during his time at NCIS. Still when they were putting grid teams together, he was one of the first volunteers because he had vital skills that could be utilized.
He had been combing through some underbrush, looking for signs of disturbance, torn cloth, or any other sort of signs of life in the area nearby but hadn't turned up much of anything. He wasn't optimistic about finding anyone today, but he wasn't going to give up that easily. He would keep trudging through the dirt, trees, and over whatever he had to until the search was called off. You didn't leave someone behind in Gibbs' world.
Gibbs had just turned to head around and back in toward town when he stopped walking. He turned his head and slowed his breathing just slightly -- so he could hear better. His gaze darted back and forth as he listened to the air around him. Certain that he had heard someone, he started off in the direction he was sure the voice had come from.
"MAKE SOME NOISE, SO I CAN FIND YA!" He yelled in response. If he were close enough, they would hear him. And if they didn't have the strength to yell again, they could make some sort of a ruckus so he could track easier.