Patent ID: 8139777

Claim:
A noise injection system for adding comfort noise to an audio signal, comprising: a background noise estimator configured to determine a spectral content of a background noise associated with the audio signal, and generate frequency domain data; a comfort noise generator configured to generate a comfort noise signal having a randomized phase; a gain circuit configured to calculate a gain value for adjusting the comfort noise signal in the frequency domain based on the determined spectral content of the background noise to generate a gain-adjusted comfort noise signal, where the gain circuit comprises: a ripple compensator configured to adjust the gain value to compensate for an energy increase due to ripples caused by processing in an overlapping block manner; and a coherency mismatch compensator configured to adjust the gain value to compensate for data coherence mismatch caused by a phase randomization and processing in an overlapping block manner; and a combining circuit configured to combine the gain-adjusted comfort noise signal and the audio signal to generate an output signal.