Modest cough - from my story The Return, which is movieverse rather than L&C but presumably uses the same speed of sound:
"We can make endless guesses," said the President, "but there's only one expert. How do we contact Superman?"
"Shout 'Help, Superman?'" suggested Josh.
"If he's in Metropolis it would take nearly half an hour for him to hear you," said Glenn.
I think I was assuming Metropolis was about 300 miles from Washington.
