Tool to check real quality of audio files (e.g mp3, flac, wav)

Spek – https://www.spek.cc/

• The spectrum of a FLAC (lossless audio) file should go well beyond 22khz

• When the high frequencies are cut to about 20khz, that means you’re dealing with a 320kbps mp3 audio file

• High frequencies cut to 16khz equal to a bit rate of around 192kbps 

• High frequencies cut to 12khz tells you that the audio file has a bit rate of no more than 128, the lowest possible bit rate for an mp3 music file

Or use Audacity, as spek can only check mp3 one by one.