A density measurement system for measuring a density of a speech processing device including a plurality of channels each having an encoder and a decoder, where each one of the plurality of channels is coupled to another one of the plurality of channels to provide a plurality of coupled pairs. The system comprises a first signal injector module for injecting a first speech signal into a first one of each coupled pair; a second signal injector module for injecting a second speech signal into a second one of each coupled pair; a quality module connected to each decoder for measuring a quality value for each decoder; and an error module connected to each encoder for determining an error value for each encoder, wherein the system determines the density of the speech processing device based on the quality value of each decoder and the error value of each encoder.