Audio signal range

Say you plug headphones with infinitely extendable cable length to a regular MP3 player, how far will the signal travel from the player through the cable until it ceases to be heard?

Basically the maximum range comes down to a few factors:
• Minimum power required by the headphone speakers for acceptable sound.
• Maximum power output by the MP3 player.
• Power consumption of the cable (watts/metre).

Chances are you'd get some of these figures by deriving them from operating voltages and max current outputs etc.

If you have these things then you can shift them around to get:
(Maximum Output) = (Minimum Input) + (Cable Power Consumption per Metre)*(Maximum Cable Length)
Which rearranges to:
(Maximum Cable Length) = ((Maximum Output) - (Minimum Input))/(Cable Power Consumption per Metre)