Question: What is the primary purpose of introducing a pre-emphasis filter before applying the perceptual weighting filter in the Enhanced Voice Services (EVS) codec?
Option 1: To enhance the low-frequency content of speech signals for better formant structure modeling.
Option 2: To increase the high-frequency content of speech signals, mitigating the wide dynamic range between low and high frequencies.
Option 3: To reduce the computational complexity of the perceptual weighting filter by simplifying its transfer function.
Option 4: To improve the codec's robustness against background noise in voice communications.
Explanation: The correct answer is Option 2 because the pre-emphasis filter is introduced to enhance the high-frequency content of speech signals. This enhancement is crucial for addressing the pronounced spectral tilt in speech signals, which arises from the significant dynamic range between low and high frequencies. By boosting high-frequency content, the perceptual weighting filter can more effectively model both formant structures and spectral tilt, leading to improved voice quality in EVS codec applications.