Increase that to 192kb/s or use an advanced coding scheme such as AAC and the number of people who can tell the difference in double blind trials is substantially smaller. 128kb/s AAC usually scores around 4.8 on the standard ITU listening test scale: a naive interpretation of this is that 80% of the listeners rank it 5 (indistinguishable from the original sample) with only 20% ranking it 4 (disti