TTS OpenAI Models

OpenAI now supports a suite of next-generation audio models in its API, including text-to-speech (TTS) and speech-to-text, enabling developers to build rich voice agents, voice assistants, and narrators.

The key TTS model is called gpt-4o-mini-tts, which not only converts text into human-like speech but also lets you pass instructions on tone, style, or emotion (for example: “talk like a bedtime storyteller” or “sound like a professional support agent”).

This makes the voice generation much more expressive than just “reading” text.

OpenAI supports a library of built-in voices — such as Alloy, Echo, Fable, Onyx, Nova, Sage, Shimmer, and others — giving you a good variety of tone and character for your applications.

You can also control speed (how fast the AI speaks) when generating speech.

From a technical standpoint, these models are built on the GPT‑4o / GPT‑4o‑mini architecture but are specially trained for audio generation.

OpenAI claims they used reinforcement learning and distillation techniques to make smaller TTS models that still sound high-quality.

As for use cases, OpenAI’s TTS API supports:

Voice agents / virtual assistants

Audiobook narration or storytelling

Accessibility features (e.g., reading text in apps)

Interactive apps (games, learning tools)

There’s also streaming support — developers can stream the generated audio (rather than waiting for full render) in certain setups.