I see bigmac's point that if the 4 (or 8) lsbs were simply tossed away (truncated), that would not the same as orignially recording at 12 (or 8) bits.

To illustrate this, say you have two tones. One tone is large in amplitude, consuning a large percentage of the recording medium's dynamic range. The other tone is small, by itself consuming less than the range of 4 (or 8) bits, the number of bits you are later going to truncate. If you record the big tone only, then both tones together, and then the small tone alone, then simply throw away (THIS is truncation) the least significant 4 (or 8 bits), the playback result will have the large tone in the part where just the large tone was recorded (with distortion due to the truncation), the region recorded with both tones will have both tones (with distortion due to the truncation) but the region recorded with the small tone alone (which had a recorded amplitude less than the number of bits that was truncated) now has nothing.

In soundhound's orignal post in this thread, he said he truncated the least 4 or 8 bits. From what he said later, it sounds as though he did not actually truncate (chop off). Beings I am not a recording engineer, I do now know what procedure or process would be used to go from 16 bits to 12 or 8 in a non-truncating way. Of course converting back to analog and then re-digitizing with a 12 or 8 bits word length would do the trick. I have no doubt that there is a digital process that can take one from 16 bit word space to 12 or 8 bit word space(without truncation) without going through the intermediate analog state.

I remember years ago when I purchased my first computer sound card (a Turtle Beach Monterey, with I stil have but don't use because it is ISA and non-plug and play). I played aroung with recording, via the line input, various snippets of sound from an audio CD player. I recorded in 16 bits and 8 bits and compared the two. I was shocked at how good (compared to my expectations) the 8 bit recording sounded. I was expecting the 8 bit recording to sound much worse that it did.

So, when soundhound says that he has propely went from 16 bits to 12 or 8 (non-truncating), I suspect that it will be not as easy as we might think to tell (by listening only) which section of music was recorded with how many bits.

Paul

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the 1derful1

[This message has been edited by Paul J. Stiles (edited October 10, 2002).]