Objective difference grade
In digital audio, the objective difference grade is calculated by perceptual evaluation of the audio quality algorithm specified in ITU BS.1387-1. It corresponds to the subjective difference grade used in human-based audio tests.
The ODG ranges from 0 to −4 and is defined as follows:
| Impairment description | ITU-R Grade | ODG |
| Imperceptible | 5.0 | 0.0 |
| Perceptible, but not annoying | 4.0 | −1.0 |
| Slightly annoying | 3.0 | −2.0 |
| Annoying | 2.0 | −3.0 |
| Very annoying | 1.0 | −4.0 |