I wake up very early this morning, and as my wife did not want to speak with me at those hours, I had to occupy my time with a little experiment.
First aim was to find a way to verify if there is a way to verify that the process I am using to rip my CD's was properly implemented. I am using EAC with Accuraterip and an external converter for translating the files to Apple Lossless (convenience). I was a little afraid that the external converter wasn't good enough, so I read on Internet how to verify it:
1) Install Audacity
2) Import Audio File 1 (m4a file)
3) Import Audio File 2 (wav file direct from EAC)
4) Invert the first audio file
5) Mix and Render both
6) Look for any audio signal left after the process.
I was happy to verify that the process was working perfectly, and that any signal appear after the mix, as expected.
Then, I though it could be interesting to compress one audiofile from HDTracks to MP3 320 and see any difference, since in my kind of blind test I could not find any. Result: Yes, there are clearly audible differences between the files.
The software I used to convert from 96/24 to mp3 is called "Switch Sound File Converter". I do not know what algoriythm it uses, only that it is VBR.
I use the same software to downsample the 96 file to lossless 44.1/16, and using the same procedure describe above to compare the differences with Audacity, I got nothing to hear (there was information, but it was at a very low volume); if I use the lowpass filter, even as low as 5kHz, I still have audio in there. I cannot listen to it because it is really low volume, but I though any difference would be above 22 kHz.
Can anybody please explain it to me? Why I have signal as such "low" frecuency?
Edited by daniel0407 - 2/1/14 at 3:14am