---
url: >-
  https://adk.nht.io/api/@nhtio/adk/batteries/tts/_shared/interfaces/BaseTtsAdapterOptions.md
description: 'Options shared by **every** TTS engine, regardless of backend.'
---

# Interface: BaseTtsAdapterOptions

Defined in: [src/batteries/tts/\_shared/index.ts:51](https://github.com/NHTIO/ADK/blob/v1.20260718.0/src/src/batteries/tts/_shared/index.ts#L51)

Options shared by **every** TTS engine, regardless of backend.

## Remarks

Engine-specific option interfaces extend this with their own transport/engine fields (and, for
model-backed engines, a required `model`). Both fields are normalized per-engine:

* `voice` → `say -v <voice>` / `espeak-ng -v <voice>` / PowerShell `SelectVoice(<voice>)` /
  transformers.js `speaker_embeddings` when it is a string.
* `rate` is a **multiplier** where `1` is engine-normal, mapped per engine: `round(175 * rate)`
  words-per-minute for `say`/`espeak-ng` (clamped to a validated band), the documented `-10..10`
  `SpeechSynthesizer.Rate` for PowerShell, and `speed` for transformers.js.

## Extended by

* [`TransformersJsTtsAdapterOptions`](../../transformers_js/types/interfaces/TransformersJsTtsAdapterOptions.md)
* [`NativeTtsAdapterOptions`](../../native/types/interfaces/NativeTtsAdapterOptions.md)

## Properties

| Property                             | Type     | Description                                                                                                                                                                             | Defined in                                                                                                                           |
| ------------------------------------ | -------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------ |
|  `rate?`   | `number` | Default speaking-rate multiplier (`1` = engine-normal), applied when a `synthesize` call omits its own `rate`. Per-engine mapping (see the module remarks). Unset → engine-normal rate. | [src/batteries/tts/\_shared/index.ts:61](https://github.com/NHTIO/ADK/blob/v1.20260718.0/src/src/batteries/tts/_shared/index.ts#L61) |
|  `voice?` | `string` | Default voice, applied when a `synthesize` call omits its own `voice`. Per-engine semantics (see the module remarks). Unset → the engine/model default voice.                           | [src/batteries/tts/\_shared/index.ts:56](https://github.com/NHTIO/ADK/blob/v1.20260718.0/src/src/batteries/tts/_shared/index.ts#L56) |