Click here to purchase the entire book in PDF format. MUSHRA - MUlti Stimulus test with Hidden Reference and Anchors The MUSHRA test developed by the EBU is, in some ways, similar to the BS.1116 test, however, it's designed for bigger impairments. Let's say that you wanted to test 3 different codec's applied to the same signal. You give the subject the original reference, labeled "Reference" and four different stimuli to rate. One of these stimuli is an exact copy of the Reference, and the other three are the same sound, processed using the codec's under test. The subject is asked to directly rate each stimulus on a continuous 5-point scale (1. Bad, 2. Poor, 3. Fair, 4. Good, 5. Excellent) as is shown in Figure 5.21 Figure 5.21: An example of a MUSHRA user interface. The nice thing about this test is that you can get ratings of many different stimuli all in the same test, instead of one at a time like the BS.1116 test. Therefore, you get more results quicker. The disadvantage is that it's not designed for very small impairments, so if your codec's are all very good, you'll just see a lot of ``Excellent'' ratings...