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Which 'Model' for which Application? A summary of the principle assessment scenarios and the corresponding measurement algorithms applications with OPERA™ follows: This short guide can be used as a reference when uncertain which measurement algorithm to apply.

First, recall that the recommended perceptual measurement techniques always try to model the underlying subjective experiment of the corresponding listening test.
To decide which one is the proper experiment, remember to ask yourself the following questions:

> Key Questions to recall
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Do you intend to assess wide band audio signals (music signals, like mp3 etc. or bandwidth > 16kHz)?

•

If you compare your assessment to a listening test, would the subject be able to compare the test signal with the original reference signal?
>

If the answer to both questions is YES, you should apply the PEAQ algorithm.
>

If the answer to both questions is NO, you should apply the PESQ (or the PSQM) algorithm.

> Limitations If none of the above seems to apply, an experimental situation outside the scope of both measurements should probably be considered. In this case, it is always helpful to consider how subjects would behave in a listening test. In some cases, however, you may also find that even subjects would not be able to properly score the sound quality. This might for instance happen if you use artificial test tones or noise based measurements. Another issue might be that you might be interested in picking up level differences or filtering (linear distortions). Please keep in mind that without comparison to a reference signal, subjects would never be able to depict such differences, as long as they do not exceed a certain threshold. Consequently, PESQ for instance was designed in a way to compensate for level differences and linear distortions of up to 20dB (compared to the reference signal). For further details on the scope of the algorithms and limitations respectively, you may want to refer to the ITU recommendations.
> Principle Setup for a BS.1116 Listening Test
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> Principle Setup for a P.800 Listening Test
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> Continue continue [Reference Stimuli]

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