For a moment, Jack looked completely confused. He looked at the sonic and back to the Doctor and... yes, how did he know it was sonic?

But he recovered as quickly as he fell and he retuned a patronising smile of his own.

"Oh come on. You think I'm that stupid? I've been around a while. I've seen a lot of things. I can recognise sonic technology when I see it."

But no that really wasn't it, was it? He knew that device was sonic. How did he know? Did they salvage one at Torchwood? Oh that must have been it. It must have been some alien tech that fell through the rift.

"And I've seen one before," he added in a scoff.