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

# Voice Focus for Voice AI Systems

> Improving STT accuracy with Quail Voice Focus.

For voice agent applications where a single primary speaker needs to be isolated, [Quail Voice Focus](/models/voice-focus/quail-voice-focus) is the recommended model for improving downstream Speech-to-Text (STT) accuracy.

On **Quail Voice Focus**, the `enhancement_level` parameter provides fine-grained control over foreground isolation. It accepts values from `0.0` to `1.0`.

<AccordionGroup>
  <Accordion title="How it works">
    The model uses an internal probabilistic confidence estimate for its foreground isolation decisions. The `enhancement_level` parameter modulates how the model acts on this confidence signal:

    * **Lower values** bias the model toward preserving ambiguous speech. Foreground speech is always kept, but more background leakage may pass through.
    * **Higher values** shift the model toward stricter decisions under uncertainty. Competing speech and echo are attenuated more aggressively, but there is an increased risk of suppressing low-energy foreground speech.
  </Accordion>
</AccordionGroup>

## Recommended Settings

| Value           | Behavior                                               | When to use                                                                                                        |
| --------------- | ------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------ |
| `0.5` (default) | Conservative. Foreground speech is always preserved.   | When minimizing any risk of speech deletion is the top priority.                                                   |
| `0.8`           | Balanced. Optimal word error rate on challenging data. | Best starting point for most Voice AI deployments. Slightly higher chance of over-suppression in edge cases.       |
| `1.0`           | Aggressive. Maximum suppression of interfering speech. | When reducing insertions from background speakers is critical. Higher risk of suppressing quiet foreground speech. |

<Tip>
  Start with the default value of `0.5` and increase toward `0.8` if you observe STT errors caused by competing speech or background noise. The ideal setting depends on your STT provider, language, environment, and pre-processing pipeline.
</Tip>

## Best Practices

* **Use Quail Voice Focus to isolate the main speaker.** It provides the best foreground isolation for headset and handheld use cases, eliminating interfering background speech and noise.
* **Tune per STT provider.** Different engines respond differently to the same audio. Run evaluations with your specific STT model to find the optimal `enhancement_level`.
* **Monitor both insertions and deletions.** Increasing the enhancement level reduces false insertions from background speech but may increase deletions of quiet foreground speech. Find the right balance for your application.