Question: In the context of onset detection for pre-echo removal in Enhanced Voice Services (EVS) codec, how is the energy before an identified attack scaled when its magnitude exceeds the threshold?
Option 1: It is amplified to match the energy level of the current frame.
Option 2: It remains unscaled to preserve original signal dynamics.
Option 3: It is reduced to a fixed minimum energy level to prevent distortion.
Option 4: It is scaled to the level of the previous frame energy plus 6 dB.
Explanation: This scaling approach ensures that the energy preceding an onset (attack) is normalized to a level consistent with the expected signal energy growth, preventing abrupt changes that could introduce pre-echo. By matching it to the previous frame's energy plus 6 dB, the algorithm effectively smooths out the transition to the more energetic section, thus mitigating pre-echo effects in voice communications.