hermes-agent/website/docs/user-guide/features/tts.md

---
sidebar_position: 9
title: "Voice & TTS"
description: "Text-to-speech and voice message transcription across all platforms"
---

# Voice & TTS

Hermes Agent supports both text-to-speech output and voice message transcription across all messaging platforms.

## Text-to-Speech

Convert text to speech with three providers:

| Provider | Quality | Cost | API Key |
|----------|---------|------|---------|
| **Edge TTS** (default) | Good | Free | None needed |
| **ElevenLabs** | Excellent | Paid | `ELEVENLABS_API_KEY` |
| **OpenAI TTS** | Good | Paid | `VOICE_TOOLS_OPENAI_KEY` |

### Platform Delivery

| Platform | Delivery | Format |
|----------|----------|--------|
| Telegram | Voice bubble (plays inline) | Opus `.ogg` |
| Discord | Audio file attachment | MP3 |
| WhatsApp | Audio file attachment | MP3 |
| CLI | Saved to `~/.hermes/audio_cache/` | MP3 |

### Configuration

```yaml
# In ~/.hermes/config.yaml
tts:
  provider: "edge"              # "edge" | "elevenlabs" | "openai"
  edge:
    voice: "en-US-AriaNeural"   # 322 voices, 74 languages
  elevenlabs:
    voice_id: "pNInz6obpgDQGcFmaJgB"  # Adam
    model_id: "eleven_multilingual_v2"
  openai:
    model: "gpt-4o-mini-tts"
    voice: "alloy"              # alloy, echo, fable, onyx, nova, shimmer
```

### Telegram Voice Bubbles & ffmpeg

Telegram voice bubbles require Opus/OGG audio format:

- **OpenAI and ElevenLabs** produce Opus natively — no extra setup
- **Edge TTS** (default) outputs MP3 and needs **ffmpeg** to convert:

```bash
# Ubuntu/Debian
sudo apt install ffmpeg

# macOS
brew install ffmpeg

# Fedora
sudo dnf install ffmpeg
```

Without ffmpeg, Edge TTS audio is sent as a regular audio file (playable, but shows as a rectangular player instead of a voice bubble).

:::tip
If you want voice bubbles without installing ffmpeg, switch to the OpenAI or ElevenLabs provider.
:::

## Voice Message Transcription (STT)

Voice messages sent on Telegram, Discord, WhatsApp, Slack, or Signal are automatically transcribed and injected as text into the conversation. The agent sees the transcript as normal text.

| Provider | Quality | Cost | API Key |
|----------|---------|------|---------| 
| **Local Whisper** (default) | Good | Free | None needed |
| **OpenAI Whisper API** | Good–Best | Paid | `VOICE_TOOLS_OPENAI_KEY` |

:::info Zero Config
Local transcription works out of the box — no API key needed. The `faster-whisper` model (~150 MB for `base`) is auto-downloaded on first voice message.
:::

### Configuration

```yaml
# In ~/.hermes/config.yaml
stt:
  provider: "local"           # "local" (free, faster-whisper) | "openai" (API)
  local:
    model: "base"             # tiny, base, small, medium, large-v3
  openai:
    model: "whisper-1"        # whisper-1, gpt-4o-mini-transcribe, gpt-4o-transcribe
```

### Provider Details

**Local (faster-whisper)** — Runs Whisper locally via [faster-whisper](https://github.com/SYSTRAN/faster-whisper). Uses CPU by default, GPU if available. Model sizes:

| Model | Size | Speed | Quality |
|-------|------|-------|---------|
| `tiny` | ~75 MB | Fastest | Basic |
| `base` | ~150 MB | Fast | Good (default) |
| `small` | ~500 MB | Medium | Better |
| `medium` | ~1.5 GB | Slower | Great |
| `large-v3` | ~3 GB | Slowest | Best |

**OpenAI API** — Requires `VOICE_TOOLS_OPENAI_KEY`. Supports `whisper-1`, `gpt-4o-mini-transcribe`, and `gpt-4o-transcribe`.

### Fallback Behavior

If your configured provider isn't available, Hermes automatically falls back:
- **Local not installed** → Falls back to OpenAI API (if key is set)
- **OpenAI key not set** → Falls back to local Whisper (if installed)
- **Neither available** → Voice messages pass through with a note to the user