Voice, language and behavior settings
Last updated: September 8, 2026
The Voice, language & behavior tab of the agent editor is the full tuning surface for how your agent sounds and behaves on a call. Change what you need, click Save settings, and the configuration syncs to the voice engine.
Voice
The voice list is dynamic: it loads live from your Retell account, so it shows exactly the voices your account can use — including ElevenLabs voices if you bring your own ElevenLabs key on Retell. Filter by name, provider or accent, and use Preview voice to listen before committing: it plays a three-second sample — enough to judge tone and accent — and stops on its own. If the list cannot load (for example Retell is not connected yet), you can still paste a voice ID manually.
Below the picker you can tune the voice itself: Voice model (TTS), Speed, Temperature (expressiveness), Volume and Emotion.
LLM model and language
The LLM Model & Language section sets the brain and the tongue: pick the LLM model the agent thinks with, and the Language it speaks and understands (default: US English).
Cost per minute and latency preview
Next to the model picker every model shows Retell's $/min, and under it a live estimate line updates as you change voice, model, noise reduction or the Advanced JSON: the per-minute cost (LLM + voice + Retell voice infrastructure, plus paid add-ons such as knowledge base, advanced denoising, PII removal or guardrails) and the expected end-to-end latency (voice + model + transcription). The same figures sit in the agent header. No test call is needed: the estimate comes from Retell's published price list, the same table Retell's own dashboard uses. Twilio telephony is not included — it is billed by Twilio on your trunk.
Two things to know:
- A
*next to the cost means one component has no published price yet: the total is a floor, not the full figure. - Once the agent has real calls, a second line shows the measured figures: the real spend per conversation minute (total cost ÷ total minutes) and the latency as p50 / p90, over the last real calls — test calls are excluded. That line is the truth; the estimate is the forecast.
Behavior
The Behavior section is a set of sliders and switches:
| Setting | What it controls |
|---|---|
| Responsiveness | How quickly the agent starts replying. |
| Interruption sensitivity | How easily the caller can talk over the agent. |
| Backchannel | Short verbal acknowledgements while the lead speaks, with a frequency slider. |
| Dynamic responsiveness / Dynamic voice speed | Let the agent adapt its pace to the conversation. |
| Allow DTMF (keypad) | Whether the agent accepts keypad tones. |
Audio, timing, transcription, privacy
Four more sections cover the rest of the call experience: Audio environment (ambient sound and its volume, noise reduction), Timing & timeouts (first message delay, end call after silence, reminders, max call duration, ring duration, voicemail detection timeout), Transcription (STT mode, specialized vocabulary) and Privacy & data (data retention).
Advanced (JSON)
Nested configurations that don't have a dedicated field — pronunciation dictionaries, custom transcription config, PII handling and similar — go through the Advanced config (JSON) escape hatch. Paste a JSON object; it is merged with the fields above at save time. It must be a valid JSON object, and the form tells you if it isn't.
The same Advanced section carries a Time zone (IANA) field: it is the voice engine's own agent time zone, unrelated to the dialer's calling window — that one lives in Retries & transfer, see Set a calling window per agent.
Voicemail: the default policy
Voicemail detection is always on — the agent never talks to an answering machine. The default policy is to hang up silently when a machine answers. If you'd rather leave a fixed message, that is configured per agent in the Retries & transfer tab — see Retry cadence, callbacks and human transfer.
On an inbound agent that tab shows only the transfer and appointment cards: calling window, redials and voicemail belong to the outbound agents whose call-backs it answers.
When changes take effect
Click Save settings and the new configuration applies from the next call — calls already in progress are not touched. The sync to the voice engine is best-effort: a momentary sync error is logged and never blocks the save.
Agents created before a platform feature shipped (for example new in-call tools) do not pick those additions up from a voice or LLM save. Use the Sync GHL tools button in the Data & GHL tab, or save the policy in the Retries & transfer tab: those two are what re-register the in-call tools, the post-call analysis and the voicemail policy on the voice engine.
Next steps
- Test your agent from the browser — hear the new voice and behavior right away.
- Prompt versions, A/B metrics and rollback — tuning the words, not just the voice.