The Dependence of Sound Quality on Components
As is known, the quality of the sound obtained with Volp depends approximately on 2 components. All algorithms selected for audio compression in IP phone models and the QoS, i.e., quality of service, features provided by the WAN environment through which the audio is transmitted are included. In a sector and environment where all manufacturers claim their products deliver the best sound quality, establishing an objective criterion to compare the sound qualities of manufacturers and select the best has become a necessity. The Mean Opinion Score (MOS) value is a system used to measure sound qualities.
Measurements in a Specially Prepared Room
According to these, during MOS measurements, a large number of people listen to recorded phone conversations in a specially prepared room and give a score between approximately 1 and 5 for the sound quality. The average of all these collected values is then calculated, and sound qualities are determined with a normal phone conversation, i.e., a MOS value of approximately 4.1, taken as a reference. These algorithm systems used for compressing sounds are one of the factors determining the quality of the resulting sounds. At the same time, in the initial stages, digital transmission of sounds is provided by the Pcm algorithm; however, with this method, sounds are transmitted at 64kbps without compression. Many phone operators use these methods to transmit normal phone conversations. Accordingly, sound quality and phone quality are termed toll quality.
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