Soniox vs. AssemblyAI

Learn why developers choose AssemblyAI over Soniox to build powerful Voice AI apps that exceed industry standards:

Dramatically lower word error rate (4.50% vs 17.39%)
Reliable speaker diarization (Soniox cpWER is 112%)
Comparable real-time latency with far higher accuracy

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Universal-3 Pro

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At a glance: Soniox vs. AssemblyAI

Model

AssemblyAI Universal-3 Pro

Soniox Speech-to-Text

Word error rate (average)

4.50%

17.39%

Accented English WER

5.62%

53.48%

General speech WER

6.29%

7.55%

Speaker diarization (cpWER)

33.34%

112.28%

Streaming latency (P50)

256 ms

249 ms

Go beyond transcription with Assembly's full Voice AI Infrastructure

Best-in-Class Accuracy

Universal-3 Pro is the most accurate, controllable model on the market, with industry-leading accuracy on real-world audio—noisy environments, accents, and technical vocabulary—plus best-in-class recognition of names, emails, and numbers.

Realtime Streaming

Ultra-low-latency streaming transcription (~300ms) purpose-built for voice agents, with immutable transcripts and native code-switching.

Speaker Diarization

Built-in speaker labels on pre-recorded and streaming audio, with each word in the transcript associated to its speaker.

Lower, Usage-Based Pricing

Pay only for what you use—$0.21/hr batch and real-time from $0.15/hr—with $50 in free credits and no minimum commitments or contracts.

LLM Gateway

Route 25+ leading LLMs through one OpenAI-compatible API to build Q&A, summaries, extraction, and agentic workflows on your transcripts.

Speech Understanding

Layer summarization, sentiment analysis, topic detection, and auto chapters on top of every transcript.

PII Redaction & BAA

Detect and redact PII from transcripts and audio, and sign a BAA for apps that process PHI.

Proven Reliability and Security

Deploy on infrastructure that processes millions of hours daily, with 99.9% uptime, unlimited concurrency, and SOC 2 Type 2, ISO 27001, PCI DSS, and GDPR.

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Get your free API key and ship your first transcript in minutes—no commitments or minimums.

Ready to outgrow Soniox?

Switch to dramatically higher accuracy and reliable diarization—without giving up real-time latency.

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The customer experience with our previous provider had significant room for improvement—the pricing model wasn't ideal for our needs, we encountered some concurrency constraints, and the customer service response times were longer than we hoped.

Mark Barbir, CEO at Earmark

Playground

We're not playing around—but you can

Test our best-in-class speech-to-text and voice agent models in our no-code playground.

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Frequently asked questions

: AssemblyAI is far more accurate in AssemblyAI’s benchmarks (assemblyai.com/benchmarks): Universal-3 Pro records a 4.50% average word error rate versus 17.39% for Soniox. Soniox’s average is pulled up by hard cases like accented English (53.48% versus 5.62% for AssemblyAI).
: Compare diarization error rate (cpWER) on multi-speaker audio. In AssemblyAI’s benchmarks, Universal-3 Pro records a 33.34% cpWER versus 112.28% for Soniox—a level that makes reliable speaker labels difficult—so AssemblyAI is the safer choice for multi-speaker audio.
: AssemblyAI matches Soniox on speed while being far more accurate. Universal Streaming returns transcripts in about 256ms (P50) versus ~249ms for Soniox in AssemblyAI’s streaming benchmarks, so accuracy—not latency—is the deciding factor.
: AssemblyAI keeps low real-time latency but adds dramatically higher accuracy, reliable speaker diarization, audio intelligence, the LLM Gateway, and a BAA for apps that process PHI—all through one managed API.
: AssemblyAI’s pre-recorded transcription is $0.21 per hour and real-time starts at $0.15 per hour, with $50 in free credits and no minimum commitments. You’re billed per second of audio, so you only pay for what you use.
: Yes. AssemblyAI offers a simple REST API and SDKs in Python, TypeScript, Go, Java, and Ruby, plus $50 in free credits to test on your own audio before switching.