Background noise is modeled from an input signal comprising a desired signal and a plurality of undesired signals. At least one of the signals that comprise the input is processed to generate a signal-to-noise ratio. An articulation index is generated for the at least one of the signals that is processed. A spectrum of a speech segment is generated to improve intelligibility and quality of the speech segment based on the articulation index. A shaping logic may adjust the spectrum of the speech segment based on a comparison of the articulation index to a plurality of predetermined thresholds. Modeling of the background noise comprises modeling a tilt of the background noise.