What is Perceptual Noise Substitution and How it is used in AAC?
2.2.1 Perceptual Noise Substitution(PNS)
The PNS tool increases the coding efficiency of AAC by representing noise-like signal components with a compact parametric representation instead of coding the exact waveform. Each noise-like scale factor band is represented by a noise substitution flag and the total power of its spectral coefficients, that are not quantized and transmitted. The decoder generates random numbers replacing these coefficients with the received total power.