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Nappai Documentation

OpenAI TTS

OpenAI TTS is one of the components that give a voice agent its voice: it turns the agent’s answers into audio for the caller to hear. It uses OpenAI voices.

It plugs into the TTS connector of the Voice Agent node. It holds the voice settings the agent uses on every call.

When to use it

  • The agent’s model is already from OpenAI and you want to use the same credential for the voice.
  • You want to describe in words how the agent should sound.
  • You want to adjust how fast the agent speaks.

Configuration

You need an OpenAI API credential with your OpenAI account key. See Credentials.

FieldWhat it does
Credential (required)The OpenAI API credential used to connect to the service.
VoiceName of an OpenAI voice: alloy, ash, ballad, coral (default), echo, fable, nova, onyx, sage or shimmer.
ModelThe OpenAI voice model. Default: gpt-4o-mini-tts.
SpeedSpeaking pace. 1.0 is the voice’s natural pace; higher is faster and lower is slower. Accepts 0.25 to 4.0. Default: 1.0.

Advanced options

FieldWhat it does
Voice StyleHow the voice should sound, in plain words: for example “warm and unhurried” or “brisk and professional”.

Output

The TTS output holds the voice settings. It connects to the TTS connector of the Voice Agent node, or to Fallback TTS when you turn on Fallback Engines and want it as a backup. The editor will not let you plug it into an STT connector by mistake.

Example

An accounting firm wants a serious, clear voice to answer its clients’ questions.

  1. Add OpenAI TTS and connect it to the TTS connector of the Voice Agent.
  2. In Credential, choose the OpenAI API credential.
  3. Leave Voice as coral and write in Voice Style: “professional, clear and calm”.
  4. Test the agent in the playground and listen to how it sounds.

Good practices

  • OpenAI bills the usage to your own OpenAI account. Check your usage there.
  • The differences between local and cloud voices are explained in Quality, noise and latency.