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

# Neuphonic

> Python API reference for the neuphonic text-to-speech plugin.

<Card title="Usage guide" icon="book" href="/plugins/tts/neuphonic" horizontal>
  Setup, environment variables, and Python/JavaScript/Go usage examples.
</Card>

## NeuphonicTTS

Neuphonic text-to-speech provider for low-latency, streaming voice synthesis.

Synthesizes audio from text using Neuphonic's hosted TTS service, with
selectable voices, multilingual support, and configurable output sampling rate.

### Constructor

```python theme={null}
NeuphonicTTS(*, api_key: 'str | None' = None, voice_id: 'Optional[str]' = None, lang_code: 'str' = 'en', sampling_rate: 'int' = 22050, **kwargs) -> 'None'
```

<ParamField path="api_key" type="str | None">
  Neuphonic API key. Falls back to the `NEUPHONIC_API_KEY` environment variable when omitted.
</ParamField>

<ParamField path="voice_id" type="Optional[str]">
  Voice identifier (a UUID string from your Neuphonic voice library). The chosen voice also determines which underlying model is used. Defaults to `None`, letting Neuphonic select a default voice.
</ParamField>

<ParamField path="lang_code" type="str" default="en">
  Language code for synthesis. Defaults to `'en'`. Other supported codes include `'es'`, `'pt'`, `'fr'`, `'de'`, `'zh'`, `'ja'`, `'ko'`, and `'ur'`.
</ParamField>

<ParamField path="sampling_rate" type="int" default="22050">
  Output audio sampling rate in Hz. Defaults to `22050`. Valid values: `8000`, `16000`, `22050`, `24000`.
</ParamField>

### aclose

```python theme={null}
def aclose(self) -> 'None'
```

Release any resources held by the provider.

### emit

```python theme={null}
def emit(self, event: 'T', *args: 'Any') -> 'None'
```

Emit an event, invoking all registered handlers with the given arguments.

Handlers are called in registration order. Coroutine handlers are
scheduled on the running event loop. If the emitter is closed, the call
is a no-op.

<ParamField path="event" type="T" required>
  The event to emit.
</ParamField>

### interrupt

```python theme={null}
def interrupt(self) -> 'None'
```

Interrupt and cancel the current synthesis for the active session, if any.

### off

```python theme={null}
def off(self, event: 'T', callback: 'Callable[..., Any]') -> 'None'
```

Remove a previously registered handler for an event.

If the handler is not registered for the event, the call is a no-op.

<ParamField path="event" type="T" required>
  The event the handler was registered for.
</ParamField>

<ParamField path="callback" type="Callable[..., Any]" required>
  The handler to remove.
</ParamField>

### on

```python theme={null}
def on(self, event: 'T', callback: 'Callable[..., Any] | None' = None) -> 'Callable[..., Any]'
```

Register a handler for an event.

Can be used directly by passing a callback, or as a decorator when
`callback` is omitted.

<ParamField path="event" type="T" required>
  The event to listen for.
</ParamField>

<ParamField path="callback" type="Callable[..., Any] | None">
  The handler to invoke when the event is emitted. If `None`, a decorator is returned that registers the decorated function.
</ParamField>

<ResponseField name="returns" type="Callable[..., Any]">
  The registered callback when `callback` is provided, otherwise a decorator that registers and returns the function it wraps.
</ResponseField>

### on\_first\_audio\_byte

```python theme={null}
def on_first_audio_byte(self, callback: "'Callable[[int, int], Awaitable[None] | None]'") -> 'None'
```

Register the callback invoked when the first audio byte is produced.

<ParamField path="callback" type="'Callable[[int, int], Awaitable[None] | None]'" required>
  A callable, optionally async, invoked with synthesis timing information when the first audio byte is emitted.
</ParamField>

### synthesize

```python theme={null}
def synthesize(self, text: 'Any', **kwargs: 'Any') -> 'None'
```

Synthesize the given text into speech.

Implementations should convert the text to audio. The default behavior
forwards the text to the active session for playback when one is present.

<ParamField path="text" type="Any" required>
  The text to synthesize; coerced to a string if needed.
</ParamField>