Technical Information Regarding Testing Protocol

The online survey has a [very] general upward difficulty curve. All source materials are verified as CD-quality [16-bit, 44.1kHz] or above. Specifically, Questions 13-19 make use of EBU SQAM (Subjective Quality Assessment Materials) are losslessly encoded and sourced online from the EBU website: https://tech.ebu.ch/publications/sqamcd

The questions in the survey are variously comprised of the original source files at CD quality and a number of different compressed versions. These range from AIFF 1411 kbps and .mp3 320kbps down to .mp3 112kbps. Each of these files have been individually tested in a professional mastering environment and in a non-blind A/B test an audible difference was found to be present throughout the .mp3 range on a number of listening systems. However, this survey and its accompanying controlled test (performed at Confetti ICT in Nottingham, UK) aim to establish in a blind scenario whether participants from various demographics can in fact perceive this difference. The codecs used are split between Magix' Samplitude .mp3 converters and iTunes .mp3 and AAC converters. The test includes some control questions, where two identical files are used. Questions bounced from Samplitude to PCM .wav.