Recommendation ITU-T P.834 gives a methodology for deriving equipment impairment factors (Ies)for digital signal processing devices, namely low bit-rate codecs.The Ie values are intended to be used as an input to the E-model (see Recommendation ITU-T G.107).The methodology specified in this Recommendation makes use of instrumental models (so-called"objective methods"),e.g.,of the model defined in Recommendation ITU-T P.862.It is to be considered as supplementary to the methodology based on auditory listening only tests,described in Recommendation ITU-T P.833.It will provide valid Ie values only for those codecs for which the used instrumental model produces meaningful estimations.This Recommendation includes an electronic attachment containing speech material.