This document gives the detailed requirements for the correct operation of the background acoustic noise evaluation, noise parameter encoding/decoding and comfort noise generation for the AMR Wideband (AMR-WB) speech codec during Source Controlled Rate (SCR) operation. The requirements described in this document are mandatory for implementation in all UEs capable of supporting the AMR-WB speech codec. The receiver requirements are mandatory for implementation in all networks capable of supporting the AMR-WB speech codec, the transmitter requirements only for those where downlink SCR will be used. In case of discrepancy between the requirements described in this document and the fixed point computational description of these requirements contained in [1], the description in [1] will prevail.