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Due to the acoustics of the room at the near end and the volume setting, the signal level entering the echo cancellation system at B in the diagram (see Introduction) is typically lower than the reference level at A. The difference in level is referred to as the echo return loss.
In the subtraction phase of the echo cancellation process, the echo in the signal is typically attenuated by 35dB. The attenuation level achieved is referred to as the echo return loss enhancement.
If, for example, the reference signal level at A is 0dB (relative level) and the echo return loss is 10dB, the signal level of the echo reaching the far end would be -45dB.
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