So long as the audio signals convert into the voltage/ current signals or electromagnetic signals which can be transimitted.

Exactly speaking, there are two solutions based on the above reason:

One is converting changed audio signals over time ( frequency and amplitude ) into voltage/ current signals which can be transmitted in the wires whose distance is 10 kilometers or so such as wire broadcasting;

The other one is converting them into electromagnetic signals so that they can be transmitted in the air whose distance is quite limited only 10 meters around such as wireless earphone.