No abrupt cut off at 16k which you get with MP3s.
Just throwing that in for further investigations and considerations:
The 16kHz drop-off (lowpass) is only the case up to 192 kBit/s if used by the well-known and widely-used recommended community presets.
Before that bitrate, the decoder uses the bits to build a transparent - artifact free - bitstream and has to cut corners for that goal. From 192kBit/s and more, a normally set-up MP3s encoder spend the additional bitrates to include more and more frequency range.
A random 256 kBit/s MP3 that I just checked has about 19.2kHz and a VBR0/320 goes up to 21.7kHz (and random garbage at 23.8kHz) as they have no low-pass filtering. You can also have a 320 with 16kHz lowpass filter or any other random; the encoder can be told to get any values. In fact, VBR0 ("Extreme" preset in LAME) has no lowpass at all.
(https://i.postimg.cc/sDLZhr5p/Untitled-5.jpg)
(https://i.postimg.cc/gjn8Ckv2/Untitled-7.jpg)
As you can see, the 320MP3 has even a lower lowpass set than V0 (what my collection consists of). So, ironically a 320kBit/s MP3 has a 20.5kHz lowpass with LAME whilst a V0 takes everything and works with that. The quality of that stuff can be questionable though; as said many times with lossy encoders: You listen with your ears, not your eyes (as spectrograms do not say much about the quantization (quality level) of that high-frequency content at all) :)