The change of mechanical into electromagnetic waves and vice versa I know that sound is a type of mechanical wave, so the human eardrum changes mechanical energy into electronic energy (impulses) so the information may be processed by the brain.
Question: As satellites transfer info by electromagnetic waves that are also electric signals, then can we change these mechanical waves into electromagnetic waves and vice versa?
 A: Yes, a microphone is a device that takes mechanical vibrations from sound waves and turns them into electrical signals.  A loudspeaker takes electrical signals and creates mechanical vibrations of a speaker and that causes pressure oscillations in the air that we hear as sound.
Any such device that has created sound on earth from sound in a satellite e.g. the international space station, must have done what you asked about, with the information being tansmitted through space using electromagnetic waves.
A: Amending the previous answer, which refers more to air pressure, there is also the piezoelectric effect of some materials that can be used to transform mechanical waves and pressure from various other media apart from air, like solids, liquids etc., directly to electrical signals that can be then further processed.
Applications include, piezoelectric sensors used for any kind of industrial control automation, but also entertainment like the piezoelectric microphone or even piezoelectric loudspeakers, since the process can also be used in reverse. Thus an electric signal causing mechanical stress on the piezoelectric matter.
A: Sound waves have frequencies from 40 to 20000 Hz. At a sped of 340 m/s this leads to wabelengths of 8m down to 17 mm. Light waves in this frequency range have wavelengths between 7500 km and 15 km. Usually you are detecting at a much shorter length scale, at which these waves look like AC. This is also why I don't care about the length difference between my speaker cables.
