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nova-2-sonic

Released 2025-12-02

invited beta Tool calling

Amazon Nova 2 Sonic is Amazon's speech-to-speech foundation model for building natural, real-time voice conversation applications, and the Nova user guide aims it at interactive voice assistants, customer service automation, and conversational applications.

Input
audio text $0.06/M
Output
audio text $0.24/M
Audio input
$3/M
Audio output
$12/M

Provider list prices: no platform markup, pay-as-you-go. These are official list prices. Logged-in customers may see effective prices including workspace discounts on /console/pricing.

Price · where it sits among 6 comparable models

Input$0.06/M
$0.06 · nova-2-sonic GPT Realtime · $4
Output$0.24/M
$0.24 · nova-2-sonic GPT Realtime 2.1 · $24

The bar shows how this model’s price compares with every other model of the same kind on Synthorai. The cheapest and the most expensive are named at each end. These are base rates; batch, region and cache-write discounts are on the pricing page.

Specs & limits

Tokens

Context window (vendor spec) 1,000,000
Max output (vendor spec) 64,000

Audio

Languages English (US, UK, India, Australia), French, Italian, German, Spanish, Portuguese and Hindi, with automatic language detection and switching mid-session
Audio limits
  • Bidirectional streaming over InvokeModelWithBidirectionalStream
  • audio/lpcm, 16-bit, mono, base64 — 16 kHz input and 24 kHz output
  • 8-minute connection limit with a documented session-continuation pattern for longer conversations
  • in-Region inference only (us-east-1, us-west-2, eu-north-1, ap-northeast-1)
Streaming transcription Yes

Realtime

Voices Feminine- and masculine-sounding voices per locale (tiffany/matthew en-US, amy en-GB, olivia en-AU, kiara/arjun en-IN and hi-IN, ambre/florian fr-FR, beatrice/lorenzo it-IT, tina/lennart de-DE, lupe/carlos es-US, carolina/leo pt-BR); tiffany and matthew are polyglot voices that speak every supported language.
Session
  • Intelligent turn-taking with configurable endpointing sensitivity
  • graceful interruption handling without losing context
  • function calling with asynchronous tool handling (the assistant keeps speaking while tools run)
  • RAG grounding
  • mixed audio and text input in one conversation
  • 8-minute connection limit

Model

Modalities audio + text → audio + text
  • Amazon's speech-to-speech foundation model for real-time voice applications, reached through a bidirectional streaming API rather than a request/response one. Adapts delivery to the prosody of the incoming speech and code-switches languages within a single sentence
  • documented as robust to background noise and to accents in supported languages

per Amazon official docs ↗

Use nova-2-sonic in 30 seconds

OpenAI Realtime-compatible: connect over WebSocket and stream audio in, audio out. WS /v1/realtime

import asyncio, base64, json, websockets

URL = "wss://synthorai.io/v1/realtime?model=nova-2-sonic"
# Send ONLY the Authorization header — the beta protocol is retired.
HEADERS = {"Authorization": "Bearer sk-syn-..."}

async def main():
    async with websockets.connect(URL, additional_headers=HEADERS) as ws:
        # 1) configure the speech-to-speech session
        await ws.send(json.dumps({
            "type": "session.update",
            "session": {
                "type": "realtime",
                "output_modalities": ["audio"],
                "audio": {"output": {"voice": "alloy"}},
            },
        }))
        # 2) send input audio (base64 PCM16), then request a spoken reply
        await ws.send(json.dumps({"type": "input_audio_buffer.append", "audio": pcm16_b64}))
        await ws.send(json.dumps({"type": "input_audio_buffer.commit"}))
        await ws.send(json.dumps({"type": "response.create"}))
        # 3) stream the model's audio (and text) back
        async for raw in ws:
            ev = json.loads(raw)
            if ev["type"] == "response.audio.delta":
                play(base64.b64decode(ev["delta"]))   # audio out
            elif ev["type"] == "response.done":
                break

asyncio.run(main())

About nova-2-sonic

  • It is reached through a bidirectional streaming API rather than a request-and-response one, which is what makes low-latency multi-turn conversation possible; the official documentation lists a 1M-token context window and 64K max output tokens, with audio and text accepted in the same conversation and audio and text returned.
  • Voice coverage spans English in US, UK, Indian, and Australian varieties plus French, Italian, German, Spanish, Portuguese, and Hindi, offered in both masculine-sounding and feminine-sounding voices, with automatic language detection and switching; polyglot voices speak any supported language so the persona stays constant when a caller changes language mid-session.
  • Conversational behaviour is the selling point: delivery adapts to the prosody of the incoming speech, intelligent turn-taking detects when a speaker has finished, interruptions are handled gracefully without dropping context, and the docs claim robustness to background noise and to accents in supported languages.
  • Function calling and agentic workflows are supported, along with knowledge grounding on enterprise data through retrieval-augmented generation, and asynchronous tool handling lets the assistant keep speaking while a tool runs in the background.
  • One limit to design around: connections are capped at eight minutes, with a documented renewal and session-continuation pattern in the sample code for longer conversations.
  • Availability is limited to a small set of regions.
  • Synthorai serves it over the OpenAI-compatible /v1/realtime WebSocket endpoint, so official Realtime SDK clients connect unchanged.

FAQ

Is the nova-2-sonic API free to try?

nova-2-sonic is currently in invited beta: access is application-based rather than open signup. Apply from the Synthorai console; once approved, standard pay-as-you-go pricing applies with no subscription.

What is nova-2-sonic best at?

Speech-to-speech model for real-time voice conversation; polyglot voices hold one persona across language switches; connections capped at eight minutes with a documented renewal pattern. See the About section for the full picture from the vendor's own release notes.

How much does nova-2-sonic cost?

nova-2-sonic costs $0.06 per million input tokens and $0.24 per million output tokens on Synthorai. That is the provider's list price, with no platform markup.

How do I connect to the nova-2-sonic API?

nova-2-sonic is a speech-to-speech model: connect over WebSocket to wss://synthorai.io/v1/realtime?model=nova-2-sonic with the OpenAI Realtime SDK (or a raw WebSocket) and stream audio in, audio out. It is not a POST /v1/audio/transcriptions file upload. Authenticate with your sk-syn key, sending only the Authorization header (the beta protocol is retired).

How do I get access to nova-2-sonic?

nova-2-sonic is in invited beta: request access from the Synthorai console. Once approved it works like every other model: point your OpenAI SDK at base_url="https://synthorai.io/v1" and set model="nova-2-sonic".

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Every value on this page is transcribed from the vendor's own documentation, linked above, and carries the date it was checked. Prices are compared across the catalogue; specification values that vendors define differently are shown with the difference stated rather than charted. Nothing here is measured by us, and nothing is scored.

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