About two key technicals of silence suppression, which are true? (Select two Answers)

Question

Options

• AEC (echo canceller)
• BVAD (voice activity detection)
• CJB (jitter elimination)
• DCNG (comfort noise generator)

• A
  19% (5)
• B
  73% (19)
• C
  8% (2)

Explanation

Silence suppression is a VoIP bandwidth-saving technique that stops transmitting audio when no speech is detected. It relies on two core components: VAD (Voice Activity Detection) identifies whether a speaker is active or silent, triggering the suppression when silence is found; and CNG (Comfort Noise Generation) synthesizes low-level background noise on the receiving end to prevent the unsettling "dead air" that would otherwise make callers think the call dropped.

Why the distractors are wrong:

• A - EC (Echo Canceller): Echo cancellation is an independent DSP function that removes acoustic or line echo from the signal - it operates regardless of whether silence suppression is active.
• C - JB (Jitter Buffer): A jitter buffer smooths out variable packet arrival times in the network layer; it has nothing to do with detecting or handling silent periods.

Memory tip: Think of silence suppression as a two-step loop - "Is anyone talking? No → Fake it." VAD asks the question; CNG fakes the background. Both have the word "detection" or "generation" in their names - one detects speech, the other generates noise. That pairing (detect + generate) is the whole mechanism.

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