Question: In EVS (Enhanced Voice Services) codec, when rate switching involves changing the output signal's bandwidth from Super Wideband (SWB) to Wideband (WB), what post-processing technique is primarily employed to enhance perceptual quality?
Option 1: Adaptive Noise Reduction
Option 2: Blind Bandwidth Extension
Option 3: Dynamic Range Compression
Option 4: Smoothing
Explanation: According to the principles of bandwidth switching in EVS codec for maintaining perceptual quality, when transitioning from a higher bandwidth (SWB) to a lower bandwidth (WB), the technique of Blind Bandwidth Extension is utilized. This method helps in preserving the audio quality by intelligently extending the lower bandwidth signal to mimic the wider band characteristics, thus reducing the perceived drop in quality during the switch.