Possible Clues:

• By the sound of it, they're too young to get down to work
• They sound too young to get down to work
• Diggers
• The Seven Dwarfs, at work
• The Seven Dwarfs, e.g.
• People searching in vein?
• Ore diggers
• The Seven Dwarfs, by profession
• They sound too young to go underground
• Pit-crew members