This sounds like my Dah as he walked or rode behind the mob of sheep or cattle he was droving. He would whistle to his dogs and crack his whip in the air to signal the dogs to go forward or back or right or left or do anything that the dogs were capable of doing to control the mob. Whistles and whip cracks were the only sounds he could make that the dogs could hear above the din of the mob. He also had a wooden clapper that he rattled above his head to give more urgent commands."The man whistled and spoke to it with the sound of whip-lashes.