> ## Documentation Index
> Fetch the complete documentation index at: https://docs.photon.codes/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Voice call troubleshooting

> Common audio problems on Spectrum voice calls, what causes them, and how to fix them.

If calls connect but the audio is wrong and you've ruled out your own endpoint, this page is organized by the symptom you're hearing. Find it in the headings below and follow the fix. Each section is self-contained, so you can land here from a search result and still get what you need.

If your symptom isn't listed, jump to [Still stuck?](#still-stuck) for what to send us so we can trace it on our side.

## Callers hear choppy or distorted AI audio

The caller hears the AI voice as choppy or warbly, but the other direction
is clean — the AI platform's transcription and its own recording sound fine.

Spectrum uses G.711 for call audio to keep quality consistent. It's the
codec the phone network itself runs on, and it holds up on the mobile
networks most callers are on.

If your AI audio is choppy anyway, check the codec in your endpoint's
`200 OK`. It should say `PCMU/8000` or `PCMA/8000` — if it says anything
else, or it's choppy even on those, jump to [Still stuck?](#still-stuck)
and include the codec in your report.

## Audio sounds like a regular phone call, not HD

That's expected — G.711 is standard telephone quality. Consistent audio on
every call beats HD on some and garbled audio on the rest.

## One-way or missing audio

Spectrum only handles signaling. The audio itself (RTP) flows directly
between the carrier and your SIP endpoint, so when sound is missing in one
direction the problem is usually at one of those two ends:

* Make sure your endpoint (or its cloud provider) accepts inbound RTP from
  the carrier's media IPs, not just SIP signaling.
* If your endpoint sits behind NAT, it needs to advertise a publicly
  reachable address in its SDP, not a private one.
* Check your endpoint's media logs for RTP timeouts or packet-receive errors
  on the affected call.

## Still stuck?

Send us:

* Your project id (from `photon projects show`).
* The SIP Call-ID, or the call time, caller number, and dialed number so we
  can find it.
* The direction (inbound or outbound) and which side hears the problem.
* The negotiated codec from the `200 OK`, if you can capture it.
* Your downstream SIP endpoint vendor (ElevenLabs, Retell, self-hosted, …).

We'll trace the call on our side, including the exact SDP each leg saw. Email
us at [help@photon.codes](mailto:help@photon.codes) or ping us in the Discord
linked in the footer.