Factors causing voice degradation

Last Updated : Sep 21, 2016 |
Prolog information
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Keywords:
VoIP applications put severe constraints on the amount of end-to-end transfer delay of voice signal and routing. If these constraints are not met, users complain of garbled or degraded voice quality, gaps, and pops. Due to human voice perception, VoIP applications can afford to randomly lose a few voice packets and the user can still understand the conversation. However, if voice packets are delayed or systematically lost, the destination experiences a momentary loss of sound, often with some unpleasing artifacts like clicks or pops. Some general complaints and their causes are listed in the following table:
User complaints and their causes
Complaint
Possible causes and links to information
‘Talking over’ the far end
  • Packet delay and loss
  • Echo
  • Network architecture between endpoint and intermediate node
  • Switching algorithms
Echo at the near-end and far-end
  • Impedance mismatch
  • Improper coupling
  • Codec administration
Too soft or too loud voice
  • PSTN loss
  • Digital loss
  • Automatic Gain Control
  • Conference loss plan
Clicks, pops, or stutters
  • Packet loss
  • Timing drift due to clocks
  • Jitter
  • False DTMF detection
  • Silence suppression algorithms
Muffled, distorted, or noisy sound
  • Codec administration
  • Transducers
  • Housings
  • Environment
  • Analog design
Some factors causing voice degradation are:
  • Packet delay and loss
  • Echo
  • Transcoding