Question: In the EVS (Enhanced Voice Services) codec, what is the primary purpose of utilizing the Equivalent Rectangular Bandwidth (ERB) auditory scale during the downsampling/averaging process of the normalized spectrum?
Option 1: To reduce computational complexity by transforming a variable dimension vector to a fixed dimension vector.
Option 2: To model the frequency-dependent frequency resolution of the human auditory system and remove perceptually irrelevant information in the spectra.
Option 3: To enhance voice quality by amplifying high-frequency components of the speech signal.
Option 4: To facilitate efficient transmission by applying a uniform quantization scheme across all frequency bands.
Explanation: The ERB auditory scale is utilized to mimic the human auditory system's frequency resolution, which varies across different frequencies. This approach ensures that the downsampling/averaging process prioritizes perceptually relevant information, thereby maintaining voice quality while reducing the amount of data to be quantized and transmitted. While transforming a variable dimension vector to a fixed one (Option 1) is indeed a consequence of this process, it is not the primary purpose of using the ERB scale. Options 3 and 4 are incorrect as they do not accurately describe the role of the ERB scale in the EVS codec's amplitude quantization process.