Troubleshooting Latency and Delayed Audio Issues on Twilio Programmable Voice Calls

When caller or callee reports excessive delays in the call audio, this is often caused by excessive latency on the line. Call audio latency can be caused by a number of factors including delayed packet transmission or delivery somewhere along the line, or the technologies used in the call. This guide is intended to help diagnose and resolve call audio quality issues related to latency and delayed call audio.

Check for Twilio Incidents

Check the Twilio Status Page to see if there is an active incident, or an incident during the timeframe you reported issues, that could be causing your issues. For full details, please see Checking Twilio Service and API Status with the Status Page.

No incidents are listed that may be affecting calls: If you don't see an incident posted that may affect calls, then there is likely an issue elsewhere. Continue reading for additional troubleshooting.

An incident may be affecting calls: If you see an incident posted that may affect outgoing Twilio calls, please monitor the status, and then test again once the incident is resolved.

Identify the Issue

Attempt to ascertain the full details surrounding this issue:

  • Which side of the call is reporting the issue(s): caller, callee, or both?
  • Was the audio delayed the entire time, or did this occur at some point in the call?
  • Does this issue occur at the same time each call?
  • Are any parties using a speakerphone, mobile phone, or using a wireless headset or other accessory for calls?
  • Is this a Twilio Conference call?
    • Delayed audio from a conference participant's line is usually noticed by everyone except the participant with the latency on their connection.
    • Conferences require mixing, which adds some latency due to the inclusion of a jitter buffer. 
    • Conferences can be mixed in a different region than participants, which could also add latency.
  • Does this issue only occur with specific phone numbers or number types (landline, mobile, VoIP, etc.)?
  • Is there any additional call forwarding before or after the call connections to Twilio?
  • Is the phone number in-use being ported? This could add additional latency temporarily until the port is completed.
  • Does this issue only occur when calling or receiving calls from a specific region or country?
  • Do other callers/callees report similar issues?

Once you are able to answer these questions, continue reading for additional troubleshooting.

Attempt to Replicate the Issue

Attempt another test call or two between the same phone numbers, and then try using the same Twilio phone number with different caller/callee phone numbers. The goal is to determine if this was a one-off, if the issue is limited to specific phone numbers or service providers, or if there may be a larger issue that requires investigation.

Issue is always replicated: If you are able to replicate the audio latency issues on all calls in the same direction (to or from) with your Twilio phone number, we need to perform additional testing. Continue reading for additional troubleshooting.

Issue is sometimes replicated: If you are able to replicate the audio latency issues only some of the time on calls in the same direction, check for any patterns:

  • If audio quality concerns are only coming from incoming callers using a specific service provider (or a small group of providers), then escalate to the caller's service provider.
  • If audio quality concerns are only coming from outgoing callees using a specific service provider (or a small group of providers), then continue reading for additional troubleshooting.
  • If audio quality concerns are only coming from users connecting with wireless phones, speakerphones, or bluetooth accessories, audio delay issues may be related to their hardware, as these technologies add latency. Test again on a landline or other phone without using any additional accessories.
  • If no pattern can be found, collect additional examples, and then continue reading for additional troubleshooting.

Unable to replicate this issue: If you are unable to replicate the audio latency issues, it's unlikely we will be able to address this report. Continue to monitor, and restart troubleshooting as needed if additional reports are received.

Escalate to Twilio Support

If you can rule out all of the above issues, Twilio's Support team can help investigate what went wrong. Please collect 3 or more examples of calls to or from the same Twilio phone number that have reported audio latency issues from the last 24 hours, and include the following information:

  • Call SIDs
  • Description of audio quality issues
  • Variance of issues
  • Frequency of issues
  • Replication pattern

When you have collected this information, please share it with our Support team.

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