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(solid-state physics)



(1) (Metal Oxide Semiconductor) See MOSFET.

(2) (Mean Opinion Score) The quality of a digitized voice line. It is a subjective measurement that is derived entirely by people listening to the calls and scoring the results from 1 to 5. Toll quality audio is generally considered to have a MOS rating of 4 and above.

The MOS is an average of the numbers for a particular codec. Because MOS testing requires carefully prepared and controlled test conditions, the best way to get a MOS test done is to have it outsourced. See codec.

An Objective Model
The E-Model is another rating system that provides an objective measurement of quality based on packet loss, jitter and delay. The E-Model reports results as R-values. Following is an approximate relationship between MOS and E-Model quality ratings.

Subjective Interpretation         MOS  R

 Perfect                           5.0 100

 Excellent - almost all satisfied  4.5  90

 Very good - most are satisfied    4.0  80

 Good - some are dissatisfied      3.6  70

 Fair - many are dissatisfied      3.1  60

 Poor - most are dissatisfied      2.6  50

 Bad - not recommended             1.0   0