Question: In the context of Enhanced Voice Services (EVS) codec, what is the primary purpose of applying a nonlinear gain smoothing technique to the algebraic codebook gain in noise enhancement?
Option 1: To increase the energy of the excitation for all signal types
Option 2: To reduce fluctuation in the energy of the excitation specifically for stationary signals and background noise
Option 3: To amplify voiced segments in mixed voice signals
Option 4: To normalize the gain across all signal frequencies
Explanation: The nonlinear gain smoothing technique is applied to stabilize the energy of the excitation, particularly in scenarios with stationary background noise. This approach enhances performance by reducing unwanted fluctuations that might occur in such stable signal conditions, thereby improving overall voice quality.