I agree with your reasoning here. I'm genuinely interested in your interpretation of the idiom, "whistling in the dark".

I have heard this as, "whistling in the wind", taken to imply sound waves are distorted by wind patterns since sound waves use air molecules for conveyance. Whistling into the wind would tend to dampen sound waves intended for up-wind listners. Whereas, whistling with the wind tends to cause a whistle with the same decibel level as the into-the-wind variety to travel a bit further to down-wind listners.

How would the medium of light impact travel distance of sound waves? Or is there a cultural reference here that is different for me as a American english speaker?