![]() Here is a useful list of different types of CD-ROM drives showing among other things whether they correctly support C2 error pointers. You are right of course, in theory all data errors should be caught by the CD drive's error correction code, however many CD-ROM drives are known to have firmware bugs (particularly in their handling of C2 error pointers) which means that errors can and do slip through. Note that since I was editing the audio waveform itself, my changed sample would not have been recognized as an error if I had burned the file onto a CD so Reed Solomon would not have helped. No, I replayed the files in the PC I didn't burn them to CD. Very interested to hear people's thoughts on this, particularly if you think the methodology or conclusion is flawed in any way. Given the very low level of errors that can be detected, it is furthermore quite feasible that an error in one single bit would be quite audible as a click on replay, depending on its position in the corrupted word. So my conclusion from this fairly simple test is that yes, bit errors can well be audible and that even a single corrupted audio sample can be detected quite easily even if the amplitude of the error is significantly below that of the signal. It is worth pointing out that this is a near-worst-case scenario and it is quite possible that a real musical signal would render errors at this level inaudible, however that would necessarily be programme-dependent. I successively lowered the level of the rogue sample by 6dB (roughly equivalent to one bit's worth of amplitude) at a time to -12dB, -18db, -24dB, -30dB, however it was still clearly if faintly audible even at -36dB. Next I experimented with reducing the amplitude of the click to see at what point it would become inaudible. Too easy! Even at one second the resulting click was very clearly audible. ![]() My plan was to see how far into the track I could play before these data errors became audible. I changed one sample one second into the track, two consecutive samples two seconds in etc. Then using the 'Draw' tool I edited the waveform at one second intervals to introduce -6dB 'spikes' into both L and R channels. I took track 17 from Stereophile Editor's Choice: Sampler & Test CD (a 1kHz tone at -20dB) and imported it into Audactiy. Elk asked this very question in another thread so I decided to take a closer look. However, given that on an audio CD each 16-bit word (some simplification here) encodes one sample representing only 1/44100th of a second of audio it is legitimate to ask whether these errors are generally audible at all. This is particularly relevant when ripping CDs, since a data error that makes its way into the ripped file will remain there forever. As computer audiophiles we love to obsess about 'bit perfectness' ('bit perfection'?), in other words whether or not the integrity of the audio samples being properly preserved in the digital domain.
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