BS.1387

EAQUAL stands for Evaluation Of Audio Quality. It's an objective measurement technique used to measure the quality of encoded/decoded audio files. It acts in contrast to more the common place subjective testing methodology deployed using ABX and ABC/HR reference testing (frequently preferred by hydrogenaudio). It's part of the ITU-R recommendation BS.1387. Several tests have been performed using EAQUAL most notably using numerous AAC encoders to determine via a Pearson Correlation the linear relationship between human ratings and EAQUAL ratings. The results however using objective testing methodologies are still inconclusive.

Additional reading:

• EAQUAL Sourcecode linux archive of c code used to implement EAQUAL provided by Gabrial Bouvigne.
• EAQUAL Tools zip compression archive of the utility used to perform EAQUAL tests provided by Rarewares.