[I know this is not the Audacity forum, but before I go there, or look for another piece of software, I would like to hear opinions from people who maybe know something about spectrum analyzing but who happen not to use the Audacity]
I've been looking recently on some files with the usage of spectrogram in Audacity. And some strange things I've noticed
For example here is music from the same movie, both in FLAC format
File AUDIO [http://s000.tinyupload.com/?file_id=52479850709422490152] was downloaded in FLAC, encoded by me into WAV [for some simple volume editing, nothing fancy] and then encoded back to FLAC. And it sound great
File MOVIE [http://s000.tinyupload.com/?file_id=49803452994787511089] was extracted from a video by me into WAV [for some simple volume editing] and then encoded to FLAC. Unfortunately I do not remember what kind of file it was thus I do not know the quality of audio in that video. But what is important is that it sounds bad
[I know it is not exactly the same piece of music, but those two are very similar pieces with the highly noticeable difference in quality that I've simply came to my attention when listening to my vast music colletion]
And here is the mystery: both files show frequencies above 20 kHz; but only the AUDIO sound like it. The MOVIE files looks a little different in the spectrogram [less packed,] but having audio over the 20 kHz line it sounds more like around 15 kHz. How can that be possible?
Another example is the GAME file [http://s000.tinyupload.com/?file_id=03517080551115415325]
I do not remember the origins of it, but I have it described as being a ripped audio from a Nintendo 64 videogame [released in 1997]. But I know for sure that this rip was not done by me, so almost for sure it was downloaded it a FLAC format and the encoded to WAV and back to FLAC [only by mistake I would encode WAV made from MP3 into FLAC]
And the question here is: how is it possible for this file to have frequencies around 24 kHz; and at the same time to sound like something with 10 kHz [which would be expected as it do comes from an old game from a low tech platform]?
Spectrogram is suppose to show fake lossless audio files [for example MP3s encoded to FLAC]. But this screenshot bares the proof of doing the other way around- showing low quality sounds as lossless: