Question: In the Enhanced Voice Services (EVS) codec, how are partition energies utilized for noise estimation?
Option 1: Partition energies from FFT bands only are used as input for the noise estimator.
Option 2: Partition energies from both FFT and CLDFB bands are concatenated into a single array to serve as input for the noise estimator.
Option 3: The higher of the partition energies between FFT and CLDFB bands is selected for noise estimation input.
Option 4: Partition energies are computed jointly for FFT and CLDFB bands without separation.
Explanation: This is correct because, according to the EVS codec's detailed algorithmic description, partition energies are calculated separately for FFT (Fast Fourier Transform) and CLDFB (Complex Low Delay Filter Bank) bands. These separate energy calculations are then combined into a single array, which serves as the input for the subsequent noise estimation process. This approach ensures that both spectral analysis methods contribute to the noise estimation, potentially enhancing the accuracy of voice service quality assessment.