Sound quality

The quality of sound on your VoIP line can be affected by a few factors:

  • Internet Connection
  • Phone
  • Network

Internet Connection

  • Bandwidth 
  • Sharing a connection amongst computers and SIP devices An internet connection being shared amongst VoIP phones and PC’s is never recommended. It is very difficult to control how a shared connection is being used – sending a single email, for example, could utilise the entire bandwidth of the connection, leaving little to no bandwidth for voice calls. This is where call quality degradation is experienced. Othos insists on a dedicated, voice-only connection for your SIP devices (see Recommended Connections)
  • Poor connection: latency, jitter, packet loss, and type of connection
    Diagnosing a poor connection:
    Before attempting any diagnoses, we always recommend restarting your connection and devices before testing to see if the issue still persists
    Perform a Connection Quality Test (refer to Connection Quality Test)
    Noting your results, consult the following table

What is acceptable?
Latency is the delay of the speaker’s voice getting to the listener’s ear. Voice data packets arrive, but they arrive slowly. Latency often sounds like an echo.
Latency should not spike (intermittently rise and dip), and should not exceed 100ms if optimal call quality is to be achieved.
Jitter is like latency in that the voice packets are delayed; however, the delay is unpredictable. Jitter makes the content of the call hard to understand – with audio being poor or scrambled.
The maximum allowable duration of jitter is 40 ms before deterioration occurs.
Packet loss
Packet loss is just what it sounds like — a voice data packet never arrives. The call can become extremely garbled and inaudible when packets are lost.
The only acceptable level of packet loss is 0%, as any level of packet loss will severely deteriorate voice quality.
Type of connection
Most ISP’s are designed for web surfing and not VoIP advantages. Transporting voice packets is different and requires an additional set of internet protocols that your ISP may not be providing.
The solution here is to introduce a voice-only connection which is dedicated solely for VoIP traffic. A Business Class High Speed connection is also in most cases a suitable choice.


  • Handsets and headsets can cause sound issues. If you are having sound problems on an individual telephone, try testing from another extension, or switching out pieces of equipment (such as the monophone or headset).
  • Interference from large and small electronic appliances can cause sound quality problems. Avoid having electronic devices too close to your phone.
  • Crossed or tangled cables can cause feedback. For example, if your headset cable is crossed or tangled with your cellphone charger cable, sound issues may be experienced.
  • Make sure that the volume on the device is set high enough


Your network involves many aspects such as cabling, switches, routers, cabinets, hubs, patch panels, firewalls. etc.

Check if the hardware and configurations are correct and if all devices within your unique network are working accordingly.