instead of filling up the Toy thread with more "tech" talk, here's a visual guide based on Baby Loves That Way, which is a Toy-era track (albeit one that is a different mix on the official release), chosen because it appears to be available in a genuine lossless version, unlike some of the b-sides which have been filtered above 16kHz (see Toy thread).
using the Japanese Slow Burn EP as my source, i ripped to wav in EAC to ensure i got an accurate rip. i opened the file in Cool Edit Pro (earlier version of Audacity) and here is the result of a spectral view:
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baby loves that way (WAV).jpg [ 581.07 KiB | Viewed 1439 times ]
as you can see, the window is filled with the music, right to the 22kHz line.
i then saved the file as an mp3 at a constant bit rate of 320kbps. here's a screen shot of that:
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baby loves that way (320).jpg [ 571.54 KiB | Viewed 1439 times ]
we can see the "lossy giveaway" of a clearly visible cut off at 16kHz, with a spatterring above this line. frequencies over 16kHz can't really be heard by most people (the younger we are the better we hear them), hence the difficulty in hearing any difference between a 320kbps mp3 and a CD.
using the original wav rip again, i saved at 192kbps mp3...
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baby loves that way (192).jpg [ 538.5 KiB | Viewed 1439 times ]
there are still some visible lines above 16kHz but they are reduced from the 320. what isn't obvious is the appearance of "holes" within the frequencies BELOW the 16kHz line. so, i took a close-up of the same 10 seconds from the 320 (top) and 192 (bottom) versions, and you'll see there are black areas visibly appearing in the 192:
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baby 10 seconds mp3 320.jpg [ 559.82 KiB | Viewed 1439 times ]
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baby 10 seconds mp3 192.jpg [ 538.88 KiB | Viewed 1439 times ]
this gives a clear view of how mp3 compression works, filtering out parts of the music to reduce the file size. as was shown in the Toy thread, once the mp3 reaches 128kbps there is rarely anything at all above 16kHz. once it reaches 96kbps, there is a new drop off, with nothing above 14kHz:
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baby loves that way (96).jpg [ 448.6 KiB | Viewed 1439 times ]
hopefully that's clear enough. once this filtering has been done, it can't be undone, so a rip of a CD burned from mp3s will still show the same characteristics when viewed in an editing program like this.
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