For this challenge, we are given a wav file. 
Link: https://github.com/joeyjon123/riftCTF/blob/master/chall3.wav
Listening to the audio, there doesn't seem to be anything unusual. Our next step is to open the file in Audacity and check the spectrogram.
We can read the flag from the spectrogram.
Flag: riftCTF{Music_is_Fr33d0m}