Empathic Voice Interface (EVI)

Phone calling

Guide to enabling phone calling with the Empathic Voice Interface (EVI).

This guide details how to integrate Twilio with the Empathic Voice Interface (EVI) to enable voice-to-voice interactions with EVI over the phone.

Currently, only inbound phone calling is available for EVI - you cannot call people using an EVI number, and will only receive calls. If you are interested in outbound phone calling, please contact the Hume team at hello@hume.ai.

Twilio Console Setup

By following the steps below, you can set up a Twilio phone number to connect with EVI.

Create Twilio phone number

Log into your Twilio account at Twilio Console. Navigate to Phone Numbers > Manage > Active Numbers > Buy a New Number and purchase a phone number of your choice.

A Twilio account is required to access the Twilio console. Should you run into any issues creating a phone number, please refer to Twilio’s documentation.

Setup webhook

  1. After purchasing your number, return to the Active Numbers section and select the number you intend to use for EVI.
  2. Create a configuration for EVI by following our configuration documentation, and save the config ID.
  3. Configure the webhook for incoming calls by setting the following webhook URL, replacing <YOUR CONFIG ID> and <YOUR API KEY> with your specific credentials: https://api.hume.ai/v0/evi/twilio?config_id=<YOUR CONFIG ID>&api_key=<YOUR API KEY>.

Call EVI

With your Twilio phone number registered, and the EVI webhook set up, you can now give the number a call to chat with EVI.

All of EVI’s core features are available through phone calls. However, phone calls do have two primary limitations:

  1. Latency: transmitting the audio through our Twilio integration adds a few hundred milliseconds, making interactions with EVI slightly slower.
  2. Audio quality: web audio commonly utilizes a higher quality standard of 24,000 Hz. However, due to the compression required for phone conversations, telephony audio adheres to a standard of 8,000 Hz.


If you encounter issues while using Twilio with EVI, consider the following troubleshooting tips:

  • Invalid config ID or API key: verify that the config ID and API key used in the webhook URL are correct and active.
  • Exceeded simultaneous connections: if the usage exceeds our rate limits, consider reaching out to Hume support for possible adjustments or upgrades.
  • Run out of Hume credits: if your Hume account has run out of credits, you can purchase more credits to support EVI conversations in your account settings. If you are interested in bulk pricing for EVI, please reach out to Hume support for more information.

If you encounter issues using Twilio, you can check your Twilio error logs to understand the issues in more depth. You will find these logs in your console, in the dashboard to the left under Monitor > Logs > Errors > Error Logs. See a list of Twilio errors in their Error and Warning Dictionary.