From Hydrogenaudio Knowledgebase
EAQUAL stands for Evaluation Of Audio Quality. It's an objective measurement technique used to measure the quality of encoded/decoded audio files (very similiar to PEAQ). 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 on a given set of test samples. The results, however when using objective testing methodologies are still inconclusive and mostly only used by codec developers and researchers.
 Testing Using EAQUAL
As of version 0.1.3alpha, the -h argument can be used to find out how to use eaqual (ex: eaqual -h).
To compare a test wave file to a reference wave file, one can use for example: eaqual -fref ref.wav -ftest test.wav.
 Interpreting the Results Output by EAQUAL
The results of EAQUAL are interpreted using what is known as an ODG score.
Note: this information needs to be expanded.