210-060 · Question #234
A user reports that during calls they hear excessive hissing when neither party is talking. Which option is one cause of this noise?
The correct answer is C. VAD. VAD (Voice Activity Detection) is the cause. VAD is a feature that detects silence in a voice stream and suppresses audio packets during quiet periods to conserve bandwidth. To compensate for the sudden absence of audio (which would make the call feel 'dead'), the receiving…
Question
A user reports that during calls they hear excessive hissing when neither party is talking. Which option is one cause of this noise?
Options
- AQoS
- BLoPS
- CVAD
- DEPL
- ESRST
How the community answered
(45 responses)- A4% (2)
- B2% (1)
- C84% (38)
- D9% (4)
Explanation
VAD (Voice Activity Detection) is the cause. VAD is a feature that detects silence in a voice stream and suppresses audio packets during quiet periods to conserve bandwidth. To compensate for the sudden absence of audio (which would make the call feel 'dead'), the receiving endpoint generates Comfort Noise (via CNG - Comfort Noise Generation). If VAD/CNG is misconfigured, the codec parameters are mismatched, or the comfort noise level is set too high, the generated noise can manifest as an audible hiss or static during periods of silence - even when neither party is speaking.
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