Hey, I have created agent for the Debt Support The issue i am getting in inbound call that the customer does not understands the voice of the Agent . The Agent's voice is choppy and so much distortion. Here is the call IDs and recordings below: 019bf277-6597-722c-8766-02acaa857c94 019bf2ca-99fb-7991-93af-da92d215c899 https://storage.vapi.ai/019bf277-6597-722c-8766-02acaa857c94-1769299502235-eed7aa84-de0e-438e-a7ea-48f1fcb597ca-stereo.wav https://storage.vapi.ai/019bf2ca-99fb-7991-93af-da92d215c899-1769305020812-73749361-2068-45c5-b00e-e5d2f4b424ef-stereo.wav Can you help me is this the issue from the Twillio Number or the Internal glitch in VAPI and how i can solve it?

To resolve the choppy and distorted voice issue, submit a detailed report to Vapi support including your Call IDs, a brief description of the problem, and links to the audio recordings. This ensures the support team can investigate both Twilio and Vapi sides efficiently. Example report format:

Call ID: 019bf277-6597-722c-8766-02acaa857c94
Issue: Agent's voice is choppy and distorted
Audio: [link to recording]
Expected: Clear, natural-sounding agent voice

For more details, see the [Vapi issue reporting guide](https://docs.vapi.ai/issue-reporting). Source: - [How to Report Issues Effectively](https://docs.vapi.ai/issue-reporting)

Call ID: 019bf277-6597-722c-8766-02acaa857c94 Issue: Agent’s voice is choppy and heavily distorted during inbound calls, making it difficult for the customer to understand the agent Audio: https://storage.vapi.ai/019bf277-6597-722c-8766-02acaa857c94-1769299502235-eed7aa84-de0e-438e-a7ea-48f1fcb597ca-stereo.wav Expected: Clear, natural sounding agent voice Call ID: 019bf2ca-99fb-7991-93af-da92d215c899 Issue: Agent’s voice is choppy and distorted during inbound calls Audio: https://storage.vapi.ai/019bf2ca-99fb-7991-93af-da92d215c899-1769305020812-73749361-2068-45c5-b00e-e5d2f4b424ef-stereo.wav Expected: Clear, natural sounding agent voice Context: I have created an agent for Debt Support and am consistently facing this issue on inbound calls. Customers are unable to clearly understand the agent due to severe distortion and choppy audio. Request: Could you please help confirm whether this is related to the Twilio number or an internal VAPI issue, and advise on the best way to resolve it?

To confidently say “this is Twilio, not VAPI”: Record two calls: Same agent 1. One via VAPI-managed number 2. One via Twilio inbound Compare: Agent voice clarity, Interruptions, Warble/chop artifacts Share clips here.

Hi, Thanks for sharing the call IDs and recordings — we reviewed them and were able to identify the cause of the choppy and distorted agent voice. What’s happening This issue is coming from your ElevenLabs voice configuration, not from the Twilio number itself. Specifically: • Your ElevenLabs voice is configured with

optimize_streaming_latency = 3

, which prioritizes speed over audio quality • You’re using the

eleven_turbo_v2_5

model, which is optimized for web playback, not phone calls • When this audio is converted to Twilio’s μ-law 8kHz telephony format, it becomes choppy and distorted • Logs also show

Emit Disabled But Requested Event: output

, meaning some audio chunks were blocked before delivery Recommended fix To resolve this, we recommend the following changes to your voice configuration: 1. Reduce streaming latency • Change

optimizeStreamingLatency

from 3 → 2 2. Switch to a phone-optimized model • Replace

eleven_turbo_v2_5

with

eleven_multilingual_v2

, which performs much better over PSTN calls Here’s an example configuration you can copy:

"voice": {
  "provider": "11labs",
  "voiceId": "dN8hviqdNrAsEcL57yFj",
  "model": "eleven_multilingual_v2",
  "optimizeStreamingLatency": 2
}

Fallback option You already have Cartesia configured as a fallback voice. If you still notice issues after making the above changes, we recommend testing Cartesia as the primary voice, as it’s generally very stable for telephony use cases. Please apply these updates and test a few inbound calls. Let us know how it sounds afterward, and we’ll be happy to continue tuning things if needed. Best regards, Kyle Vapi Support

Hi Kyle, Thanks for checking this. Just to clarify — I’m not using ElevenLabs at all. I’m only using VAPI’s native voice configuration with the Elliot agent, and I don’t have any custom voice models, latency settings, or external TTS providers configured on my side. So the ElevenLabs model and streaming latency settings mentioned don’t apply to my setup. Could you please re-check the call logs with this in mind and confirm what might be causing the choppy audio on inbound calls? Thanks.

Hi there, We’ve reviewed the logs and listened closely to the call recordings you shared. From our side, the audio in the recordings is clear, with the exception of the very beginning of the call. Based on this, it appears the assistant audio itself is being generated correctly, but the end user is still having trouble understanding the assistant, which points to distortion occurring downstream. Since the audio is clear in our recordings, this suggests the issue is likely happening somewhere between Twilio and the customer’s device. From Vapi’s side, we are successfully sending the audio packets to Twilio, but something in the Twilio → customer path appears to be malfunctioning. To help narrow this down, here are a few questions we recommend investigating on the Twilio side: • Have you tested the same setup using a different Twilio account? • Are there any Twilio Console settings that could affect audio playback or codec handling? • Is there anything specific about your Twilio account’s region or call configuration that could be impacting audio? • Have you checked your Twilio account for any warnings, errors, or notices related to media or call quality? If you’re able to test with a different Twilio account or share any relevant Twilio-side findings, we’re happy to take another look and help interpret the results. Looking forward to your update. Best regards, Kyle Vapi Support