we have been given an audio file. The challenge speaks of spectrum. The spectrum of a signal is the signal itself in the frequency domain.
So with an online frequency analyzer https://academo.org/demos/spectrum-analyzer/ we got:


# FLAG
```
utflag{spetr0gr4m0ph0n3}
```

Original writeup (https://github.com/Internaut401/CTF_Writeup/blob/master/2020/UTCTF/Spectre.md).