Add initial sources and docs

docs/UE_EE_SAR_Audio_signal.pdf

docs/UE_elec.eng._SAR_Audio_GuideMatlab.pdf

src/empreinte_ac.mat

src/example_with_wave_file.m

src/signal_excitation.mat

src/simule_piece.m

src/wav/Thankyouforcontac.wav

src/wav/nylon-guitar.wav

src/wav/piano_chord.wav

src/wav/single_tone_cello-a3.wav

src/wav/single_tone_celtic-harp-a3.wav

src/wav/single_tone_clarinet-a3.wav

src/wav/single_tone_cymbal-14-hard-hit-a.wav

src/wav/single_tone_double-bass-a3.wav

src/wav/single_tone_guitar-pitch-pipe-a3.wav

src/wav/single_tone_guitar_nylon_string_a2.wav

src/wav/single_tone_guitar_nylon_string_a3.wav

src/wav/single_tone_organ-c3.wav

src/wav/single_tone_piano1.wav

src/wav/single_tone_piano2.wav