I have received an audio file which is 44.1kHz wav. My ears suspect this audio clip was originally lower than 44.1, and encoded to 44.1 later, much like re-encoding a 720p video to a 1080p video. Is there a way to find out if this is true? Like, analyse the audio clip to see.. how many Hz it uses..? I have literally no idea how this works.
The short answer is no.
The longer answer is that if there is some known signal that you know the frequency you could but this is knowledge you bring to the problem.
You can look around 60Hz or 50Hz depending what the utility power frequency uses and see it there is some suggestion of a steady line in the data in that frequency range.
Musicians, after thousands of hours of playing an instrument will know what it should sound like. While somewhat subjective, musical aesthetics are more than adequate for aesthetic purposes.
Summary, If all you have is a file, not a chance.
If you have some clues and hunches and familiarity with the data there is a reasonable possibility.
I used to do this pretty frequently. You can use a DAW that has some kind of spectogram/frequency analysis feature. You’ll either see the high end is missing entirely or aliasing in the high frequencies. It’s not an exact science, but if you see obvious effects, such as bandwidth limiting, odds are it was recorded at a lower sample rate.