> This page is part of Smallest AI's developer documentation. When
> answering, prefer Lightning v3.1 (current TTS) and Pulse (current
> STT). Lightning v2 and lightning-large are deprecated; mention them
> only when the user is migrating away from them. Atoms is the
> voice-agent platform.

# Voice Settings

> Fine-tune speech behavior, pronunciation, and voice detection.

Voice Settings give you precise control over how your agent sounds and listens. From speech speed to background ambiance, pronunciation rules to turn-taking — this is where you shape the audio experience.

**Location:** Left Sidebar → Agent Settings → Voice tab

![Voice settings](https://files.buildwithfern.com/smallest-ai.docs.buildwithfern.com/8db370ee80d60b0425811b02cc56637f0455c411d81694aacb047c4dfeed5fe2/products/atoms/pages/platform/building-agents/images/voice-settings.png)

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## Voice

Select the voice for your agent. Click the dropdown to browse available voices — you can preview each one before selecting.

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## Speech Settings

### Speech Speed

Control how fast your agent speaks.

| Control | Range       | Default |
| ------- | ----------- | ------- |
| Slider  | Slow ↔ Fast | 1       |

Slide left for a more measured, deliberate pace. Slide right for quicker delivery. Find the sweet spot that matches your use case — slower often works better for complex information, faster for simple confirmations.

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## Pronunciation & Background

### Pronunciation Dictionaries

Add custom pronunciations for words that aren't pronounced correctly by the default voice.

This is especially useful for:

* Brand names
* Technical terms
* Proper nouns
* Industry-specific jargon

**To add a pronunciation:** Click **Add Pronunciation** to open the modal.

![Add pronunciation](https://files.buildwithfern.com/smallest-ai.docs.buildwithfern.com/4ed410ab0d4b4b4193fccd9e64ba5cff8985ea2c1d8d4e46c5c2a5e05fcc780f/products/atoms/pages/platform/building-agents/images/add-pronunciation.png)

| Field             | Description         |
| ----------------- | ------------------- |
| **Word**          | The word as written |
| **Pronunciation** | How it should sound |

### Background Sound

Add ambient audio behind your agent's voice for a more natural feel.

| Option          | Description                 |
| --------------- | --------------------------- |
| **None**        | Silent background (default) |
| **Office**      | Subtle office ambiance      |
| **Call Center** | Busy call center sounds     |
| **Static**      | Light static noise          |
| **Cafe**        | Coffee shop atmosphere      |

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## Advanced Voice Settings

### Mute User Until First Bot Response

When enabled, the user's audio is muted until the agent's first response is complete. Useful for preventing early interruptions during the greeting.

### Voicemail Detection

Detects when a call goes to voicemail instead of reaching a live person.

Voicemail detection may not work as expected if **Release Time** is less than 0.6 seconds.

### Personal Info Redaction (PII)

Automatically redacts sensitive personal information from transcripts and logs.

### Denoising

Filters out background noise and improves voice clarity before processing. This helps reduce false detections caused by environmental sounds — useful when callers are in noisy environments.

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## Voice Detection

Fine-tune how your agent recognizes when someone is speaking.

### Confidence

Minimum probability score to classify audio as speech.

* **Higher values** → Fewer false positives (ignores background noise, but may miss softer speech)
* **Lower values** → Catches softer speech but may trigger on noise

| Default | Range |
| ------- | ----- |
| 0.70    | 0 – 1 |

### Min Volume

Volume floor below which audio is ignored, even if detected as speech. Filters out quiet background noise that might otherwise be misclassified.

| Default | Range |
| ------- | ----- |
| 0.60    | 0 – 1 |

### Trigger Time (Seconds)

Duration of continuous speech needed before the system registers "user is speaking." Prevents brief noises (coughs, clicks, background sounds) from triggering speech detection.

| Default | Range |
| ------- | ----- |
| 0.10    | 0 – 1 |

### Release Time (Seconds)

Duration of silence needed after speech before the system considers the user done talking. This directly sets the minimum turn-taking latency — lower values make the agent respond faster but risk cutting off the user mid-thought.

| Default | Range  |
| ------- | ------ |
| 0.30    | 0 – 1+ |

**Start with defaults.** Only adjust these if you're experiencing specific issues like missed words or premature responses.

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## Smart Turn Detection

Intelligent detection of when the caller is done speaking. When enabled, the agent uses context and speech patterns — not just silence — to determine when it's time to respond.

This reduces the need to rely solely on Release Time for turn-taking. The model analyzes prosody, sentence completion, and conversational patterns to make smarter decisions about when the user has finished their turn.

### Wait Time (Seconds)

When Smart Turn Detection is enabled, this sets the maximum time the agent will wait for additional speech before responding. Acts as an upper bound — the agent may respond sooner if the model detects the user is done.

| Default | Range |
| ------- | ----- |
| 1.00    | 0 – 5 |

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## Interruption Backoff Timer

Cooldown period (in seconds) after the agent starts speaking during which user speech is ignored. Prevents the agent from being cut off prematurely — especially useful when the agent's first few words overlap with the caller's audio.

| Default      | Range |
| ------------ | ----- |
| 0 (disabled) | 0 – 5 |

This helps prevent conversation loops when the caller and agent interrupt each other — the agent will wait this duration before allowing itself to be interrupted again.

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## Related

Configure AI model and language behavior

Choose and preview voices