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

# Telephony-grade audio (8 kHz) for IVR and phone

> Generate 8 kHz mono WAV/PCM that matches the narrowband sample rate phone networks expect for IVR and call-center playback

## Prerequisites

<AccordionGroup>
  <Accordion icon="user-plus" title="Create a Fish Audio account">
    Sign up for a free Fish Audio account to get started with our API.

    1. Go to [fish.audio/auth/signup](https://fish.audio/auth/signup)
    2. Fill in your details to create an account, complete steps to verify your account.
    3. Log in to your account and navigate to the [API section](https://fish.audio/app/api-keys)
  </Accordion>

  <Accordion icon="key" title="Get your API key">
    Once you have an account, you'll need an API key to authenticate your requests.

    1. Log in to your [Fish Audio Dashboard](https://fish.audio/app/api-keys/)
    2. Navigate to the API Keys section
    3. Click "Create New Key" and give it a descriptive name, set a expiration if desired
    4. Copy your key and store it securely

    <Warning>Keep your API key secret! Never commit it to version control or share it publicly.</Warning>
  </Accordion>
</AccordionGroup>

## Recipe

Phone networks carry narrowband audio at 8 kHz. Generating at a higher rate just forces the carrier to downsample on the way through — wasting bandwidth and often softening the result. Synthesize at 8 kHz directly and the bytes are ready to hand to your IVR or SIP stack.

Set the sample rate on [`TTSConfig`](/api-reference/sdk/python/types#ttsconfig-objects) (it is not a top-level argument) and write the WAV to disk.

<CodeGroup>
  ```python Synchronous theme={null}
  from fishaudio import FishAudio
  from fishaudio.types import TTSConfig
  from fishaudio.utils import save

  client = FishAudio()

  audio = client.tts.convert(
      text="Thank you for calling. Press one to speak with an agent.",
      config=TTSConfig(format="wav", sample_rate=8000),
  )

  save(audio, "out.wav")
  ```

  ```python Asynchronous theme={null}
  import asyncio
  from fishaudio import AsyncFishAudio
  from fishaudio.types import TTSConfig
  from fishaudio.utils import save

  async def main():
      async with AsyncFishAudio() as client:
          audio = await client.tts.convert(
              text="Thank you for calling. Press one to speak with an agent.",
              config=TTSConfig(format="wav", sample_rate=8000),
          )
      save(audio, "out.wav")

  asyncio.run(main())
  ```

  ```javascript JavaScript theme={null}
  import { FishAudioClient } from "fish-audio";
  import { writeFile } from "fs/promises";

  const client = new FishAudioClient({ apiKey: process.env.FISH_API_KEY });

  const stream = await client.textToSpeech.convert(
    {
      text: "Thank you for calling. Press one to speak with an agent.",
      format: "wav",
      sample_rate: 8000,
    },
    "s2-pro"
  );

  const chunks = [];
  for await (const chunk of stream) chunks.push(Buffer.from(chunk));

  await writeFile("out.wav", Buffer.concat(chunks));
  ```
</CodeGroup>

The output is a mono 8 kHz WAV — the standard for G.711 PCM telephony. For a headerless stream to feed straight into a SIP or RTP pipeline, switch to raw PCM with `format="pcm"`; the sample rate stays on `TTSConfig`.

```python theme={null}
audio = client.tts.convert(
    text="Thank you for calling. Press one to speak with an agent.",
    config=TTSConfig(format="pcm", sample_rate=8000),
)
```

```bash API (curl) theme={null}
curl --request POST https://api.fish.audio/v1/tts \
  --header "Authorization: Bearer $FISH_API_KEY" \
  --header "Content-Type: application/json" \
  --header "model: s2-pro" \
  --data '{ "text": "Thank you for calling. Press one to speak with an agent.", "format": "wav", "sample_rate": 8000 }' \
  --output out.wav
```

<Tip>
  8 kHz discards everything above \~4 kHz, so plosives and sibilance lose detail.
  Keep prompts short and articulate, and reserve higher sample rates (16/24 kHz)
  for VoIP or recordings that never touch the legacy phone network.
</Tip>

## Related

* [Text-to-Speech guide](/features/text-to-speech)
* [Stream TTS to a file](/developer-guide/sdk-guide/cookbook/streaming-to-file)