I would need to use a 15 meters BNC Cable (RG58) in order to measure an audio signal that goes directly to a pair of earbuds. This means, the test point would be exactly before the balanced armature speaker located in the earpiece. The idea is that I would leave a BNC jack in the DUT a connect this directly to an oscilloscope. I need this setup in order to check signal integrity during EMC Testing and we would prefer to place the oscilloscope outside the chamber.
For audio frequencies it would most likely be fine. You can see the attenuation from this chart - it would probably be less than a dB: http://www.w4rp.com/ref/coax.html
What about trying an audio recorder? You could record the audio and playback the audio later into an oscilloscope.