P3SQM P3SQM stands for "Perceptual Single Sided Speech Quality Measure", and is a new algorithm, developed for non-intrusive voice quality testing.

> Intrusive vs. Non-Intrusive Testing Intrusive test methods, like PSQM and PESQ, insert a reference signal into the device under test. Like in a subjective test, the evaluation is based on a natural voice or music sample, typically of several seconds length. A stored reference is sent through the device under test, and the received listening quality is analyzed in comparison to the original. Using natural voice or music signals for the measurement is superior than applying artificial test tones, such as sinusoidal or noise, as they do not properly model the signal characteristics during normal operation.

However, due to the fact that the reference signal has to be inserted into the device under test, such measurements are called 'intrusive'. For a telecom application this means that OPERA will generate test calls. From the perspective of a network operator, who's interest is in permanent network quality control, a 'non-intrusive' method, only based on single sided monitoring without generating traffic may sometimes be preferable. Such measures are also available but due to the missing information of the source signal, they are not as reliable and accurate as intrusive measures, but can be employed to derive a course quality indicator. Non-intrusive test methods will most likely not supersede intrusive analysis, but in the future, we expect to see a co-existence of both measures:

A Non-Intrusive measurement, like P3SQM might be applied all the time for network quality monitoring.
In the fault case, an engineer would analyze what's wrong by employing an Intrusive measurement, like PESQ, to get an accurate results for problem diagnostic.

> International Standardization progressing... Currently, international standardization is progressing under participation of OPTICOM in the ITU. We expect a new recommendation for a Non-Intrusive Voice Quality analysis method in early 2003, and will keep this section updated.