Synchronization
In Referenced Mode, the synchronization of the received audio (from the Reference Audio files) versus the internal test script is achieved based on changes in frequency of the tones in the Reference Audio file. Frequency changes are used because this parameter is relatively immune to the configuration and typical impairments of the network.
By using changes in frequency, the system is able to continuously re-established synchronization with the Reference Audio file at every tone segment. That is, as each “next” frequency in the script is encountered, the exact time position in the script is re-established, the expectation of the duration of the new frequency is known, and any significant variation before the next frequency change occurs will be reported as an “Unexpected Duration” event.