One of the available TTS models: tts-1 or tts-1-hd
Required
The text to generate audio for. The maximum length is 4096 characters.
Required
The voice to use when generating the audio. Supported voices are alloy, echo, fable, onyx, nova, and shimmer. Previews of the voices are available in the Text to speech guide.
Optional
The speed of the generated audio. Select a value from 0.25 to 4.0. 1.0 is the default.