Free Real-Time AI Voice Models Compared (2026): Gemini 3.8 Live vs GPT-Live-1 vs StepAudio 3

Two busy weeks for real-time voice AI: Google shipped Gemini 3.8 Live (two weeks ago), OpenAI put GPT-Live-1 on the API (Sept 11), and StepFun released the five-model StepAudio 3 suite (two weeks ago). These three are the models you actually benchmark against when building real-time voice dialogue, voice support, or live translation. Every number below is verified: Gemini 3.8 Live's Gemini API free tier is free for audio and text input and output, paid is $0.005/min audio in + $0.018/min audio out, 97 languages; GPT-Live-1 is free for ChatGPT free users (mini tier), the API front-end voice layer costs $0.05/minute; StepAudio 3 Realtime scores 99.7% on speech reasoning and its ASR hits a 1.7% word error rate — both #1 on Artificial Analysis. Short version: pure free usage — Gemini 3.8 Live; Chinese scenarios — StepAudio 3; full-duplex + tool-calling ecosystem — GPT-Live-1.

Free-Tier Snapshot

Gemini 3.8 Live: the most generous free tier, billed per minute

Google's models use a native voice-to-voice architecture: no "STT → LLM → TTS" cascade. Audio goes in, audio comes out — lower latency, and the prosody survives. Two variants:

• Gemini 3.8 Live — built for scale: dialogue intelligence plus near-real-time camera-frame understanding (about 1 frame/second);
• Extended Thinking — multi-step reasoning runs in the background while the model keeps streaming speech ("Let me confirm…"), with configurable thinking-budget tiers.

The pricing is the cleanest of the three: free tier is Free of charge for both audio and text input and output. Paid: audio input $0.005/min ($3.00 per 1M audio tokens), audio output $0.018/min ($12.00 per 1M); text $0.75/1M in, $4.50/1M out. Compare with OpenAI: gpt-realtime-2.1 runs about $0.019/min on audio in and $0.077/min on audio out — Gemini 3.8 Live's audio output is roughly 1/4 the price. For a 10-minute conversation: about $0.23 on Gemini vs about $0.96 on gpt-realtime-2.1.

Other key numbers: 97 languages with automatic mid-conversation switching (GPT's real-time translation is a separate model, 70+ input languages to 13 output languages); 5,000 free Google Search grounding requests per month (shared across Gemini 3.x); every generated audio file carries an invisible SynthID watermark, still detectable after editing or compression. Benchmarks: #1 on the Artificial Analysis voice quality index (82.6), Big Bench Audio 97.7%.

How to use it for free

1. Open Google AI Studio and sign in with a Google account — the free tier needs no credit card;
2. Create an API key and call gemini-3.8-live or gemini-3.8-live-extended-thinking;
3. Prefer no code: Search Live is already pushed to all users — just talk to it;
4. For apps, use the Live API (bidirectional WebSocket streaming), docs under the Live section of ai.google.dev.

GPT-Live-1: free in ChatGPT, $0.05/minute on the API

GPT-Live is now ChatGPT's default voice mode, in two tiers: paid users default to GPT-Live-1, free users default to GPT-Live-1 mini — available on iOS, Android and web. So registration in ChatGPT gets you full-duplex voice for $0: simultaneous listening and speaking, natural interruption, interjections, real-time translation. Complex questions (search, multi-step reasoning) get offloaded to GPT-5.5 in the back while the front-end conversation never stalls. Reasoning tiers: Instant / Medium / High.

The Sept 11 news is where the money matters: GPT-Live-1 is on the API, and the front-end voice layer costs $0.05/minute — a 60-minute session is about $3 (~20.2 CNY), plus whatever you pay for the back-end model (GPT-6 Astra etc.) and tool calls. It handles interruptions, pauses and background noise mid-conversation, works in phone scenarios (restaurant booking, customer support), can hook into Codex-style tooling, and delegates heavy reasoning to a back-end text model.

Published benchmarks: +30 points over GPT-Realtime-2.1 on Full Duplex Bench; #1 on the Tau3 end-to-end voice-agent test when paired with GPT-6 Astra at medium reasoning. Real deployments: language-learning platform Speak cut false interruptions during learner think-time by nearly 80% vs the previous turn-based system; a healthcare platform reported 80% less code, about 23,000 lines removed. Twelve new voices added: Quartz, Ripple, Vesper, Willow, Stone, Gleam, Meridian, Bossa, Tempo, Beacon, Delta, Cinder.

How to use it for free

• Casual users ($0): tap the mic in the ChatGPT app or web to enter voice mode — free accounts get the mini tier, with interruption support and auto visual cards for weather, stocks and sports;
• Developers (registration free, usage billed): GPT-Live-1 is on the API at $0.05/minute front-end; OpenAI's Presence templates are a quick start if you don't want to hand-roll the voice layer.

StepAudio 3: the strongest for Chinese, all five models free to try

StepFun's suite covers the whole audio pipeline with five models: Realtime, ASR, TTS, Gen and Music (released two weeks ago). Two numbers stand out: Realtime speech-reasoning accuracy of 99.7% and an ASR word error rate of 1.7% — both ranked #1 on Artificial Analysis.

• Realtime: native full-duplex — listening, reasoning and speech generation run in parallel, tool calls execute asynchronously, and the model judges conversational timing (when to jump in, when to wait);
• ASR: LLM-backed context correction for Chinese, English, dialects, mixed CN/EN speech and technical jargon;
• TTS: streaming synthesis (plays while generating), preserving intonation, emotion, pauses, even laughter and hesitation;
• Gen: one model generates voice + sound effects + ambience + background music in a single pass, with timeline control over when each element fires (dubbing workflows);
• Music: from-scratch generation, humming-to-score, cover versions, and ABC-notation multi-turn composition.

Free entry: the StepFun Voice Experience Center (stepfun.com/studio/audio) lets you test all five models online for free; the open platform (platform.stepfun.com) has free registration for an API key, with pay-per-use API billing (check the live pricing page in the console). Chinese-language scenarios — transcription, dubbing, customer support — are its home turf, and the 1.7% ASR word error rate (a #1 ranking) is the proof.

Which one should you pick?

FAQ

Bottom line

Each model owns a lane: Gemini 3.8 Live wins on free tier and cost ($0 free tier + $0.018/min audio out, 97 languages), GPT-Live-1 wins on ecosystem and full-duplex ($0 mini tier in ChatGPT + $0.05/min API front-end + a 30-point benchmark lead), and StepAudio 3 wins on Chinese and the full audio pipeline (#1 ASR at 1.7% WER + Gen's one-pass full audio stack + a free experience center). For zero-cost use, start with Gemini 3.8 Live in AI Studio. For Chinese transcription and dubbing, try the StepAudio 3 experience center first. For voice agents like support or booking, GPT-Live-1's API is the most mature option. All three landed in September 2026 — pricing and free policies can change, so verify on each vendor's site before you build.