Converting from 48 kHz to 44 kHz looses the highest frequencies [with various software]

I had this problem ever since, but it did not bother me in the past as I did not knew what exactly it meant. It goes like this

[Below I am referring to my latest case of this problem - if particular files for testing will be needed I can provide them; but I think this canbe discussed without even seeing the data]


I use DVD Audio Extractor 7.1.1 [and before that version 6.3.0] to extract stereo PCM WAV files. I set them to be saved as 48 kHz. As a result the files I get have all the frequencies visible on the spectrogram, going almost to the very top [~23.5 kHz]. But if I extract the same tracksto a 44 kHz WAV file, then the frequencies in them will go only up to ~20.5 kHz. So this is a problem of DVD Audio Extractor? I wish, it was so

Because I tried converting those better ones WAVs [48kHz] into FLACs and WVs, with both NCH Switch Sound File Converter Plus 4.35 and AIMP Converter 4.51 2080. The result was more or less the same, with minimal variations- i.e. a profound lost of high frequency data. I also tried converting those 48 kHz WAVs in Audacity 2.3.2 and Sony Sound Forge 7.0 to 44 kHz- as a result the new WAVs also lost the frequencies above the 20 kHz. And all those losses do not look like a ordinary plain cut-off line- instead of that they look "natural", as if the audio was recorder / released in that way [as opposed to being crassly compressed somewhere further down the line]


So how can this be happening? I've seen this through years over and over with all kinds of files from various sources: spectrogram shows "everything" when the file is 48 kHz, but after conversion / re-sampling it becomes more inferior than it should [loosing not only that what was above the 22 kHz level]. And yes: I double checked the settings of the output formats - it is not a case of wrong settings in multiple pieces of software; to which attests also the fact that I do not have no such problems when converting 44 kHz files that have full frequencies [they retain frequencies up to 22 kHz]

Read up on the Nyquist Limit.

So what I understood is this

It is normal that this happens? And that all of the software that I happen to use apparently have such filters that they automatically wipe those frequencies?


And so the new question wold be: is there a sense in looking for some other converters, because they might preserve those frequencies? Or should I work around that issue by using what-u-hear method for creating a new file with desired parameters?

You will know of Scotty's (of Star Trek fame) quote - "You cannot change the laws of physics, Captain!" That’s what the Nyquist Limit is like - a law of physics. If you want to keep the frequencies above 20k, you’ll have to keep your wav files at 48kHz.

Or... push the record button in an editor set up to create a 44 kHz file and then push the play button of a the 48 kHz source file?


With one song it is not a problem. With an entire album it is a drag. And there is of course the issue of possible glitches in playback and of addition of extra sounds

Hi @zerow, old house!
Did you have a look at the facts of the

?
If not, then we can stop this discussion straight away as it will not come to any result.
And if you had a look at it, then the discussion will also come to an end as
@TAC109 already said: