The main reason to get a widely spread echoes measurements is that the audio path has multiple components that results in multiple points of echo reflection.
Echoes will be generated as long as there exist imbalances in a 2-4 wire conversion and mismatch in terminal impedances. This can be found in places where the analog path is converted into digital path, components performing coding and decoding, as well as in the analog terminations of the transmission path. With that, users should create a network topology diagram showing the different components constituting the audio path and analyze the characteristics of each of these components. A good understanding of these components is needed in order to find out the sources of echoes.
There are a few criteria in echo measurement with Abacus. Users should bear this in mind when performing echo measurements:-
1. The range of echoes ERL that can be detected by Abacus is 0 - 60 dB.
2. The range of delay time is between 10 ms - 600 ms.
3. The difference in ERL between two echoes must be smaller than 35 dB.