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AI Voice & Speech Comparison

Hume AI vs. Synthflow

At a glance

At a glance

Hume AI

Best for

Best for apps and content that need expressive, emotionally aware speech and real-time voice interactions.

  • Freelancers
  • Small and mid-sized
  • Enterprise

Synthflow

Best for

Best for contact centres and outsourcers that want phone agents built, branded and launched under one contract.

  • Enterprise

Cataleo does not name a winner. Both statements come from the vendors themselves.

Full Comparison

Criterion Hume AI Synthflow
Starting price lower value Free tier; paid from $3 / month Paid tiers are metered by monthly TTS characters and EVI minutes. From $30,000 / year Enterprise contracts start there and are scoped around call volume, concurrency, telephony setup, integrations, security needs and launch support. No self-serve tier is published.
Free trial Free tier with 10,000 TTS characters and 5 minutes of EVI per month Not stated
Commercial use Yes Yes, under an enterprise contract
Output Expressive text-to-speech (Octave) and empathic speech-to-speech (EVI) Voice and chat agents for inbound and outbound phone calls, including white-labelled agents resold under a partner's brand
API Yes Yes, a public Platform API, plus an MCP server for MCP-capable clients
Hosting Not stated Cloud, with region-based hosting
Voice cloning Yes, from about 15 seconds of audio Cloning happens in ElevenLabs, not in Synthflow. The voice selector offers Synthflow's own TTS with twelve built-in voices and the ElevenLabs models from Turbo v2 and Flash v2.5 up to v3; a cloned or provider-specific voice is added through Imported > Import Voice by pasting the provider voice ID, or by connecting your own ElevenLabs API key so that account's custom voices appear in the selector. The vendor warns that a synthesiser model your own ElevenLabs plan lacks can mean lower quality or higher latency on your key
Real-time use Yes, Octave 2 streaming with latency as low as about 100ms Yes, live inbound and outbound calls, with IVR handling for outbound agents, voicemail and silence handling, in-call SMS and WhatsApp messaging, and WhatsApp Business calling. The vendor states 99.99% uptime on its own telephony infrastructure
Languages Octave 2 in 11 languages Over 30 languages are listed in the documentation, plus a multilingual mode that switches between English, Spanish, French, German, Hindi, Russian, Portuguese, Japanese, Italian and Dutch within a single call. Speech recognition runs on Deepgram or Synthflow's own engine, which the vendor recommends for non-English
Speech-to-speech and dubbing Yes, the EVI empathic voice interface Not documented. The voice documentation covers text-to-speech for live agents, with a speaker and a synthesis model chosen per agent, and carries no speech-to-speech conversion and no dubbing
Editing and controls Voice design from text prompts (English), plus emotional expression from context Flow Designer, a node-based canvas with conversation, message, branch, jump and custom action nodes, or a simpler prompt builder, plus a multi-agent system for several flows behind one agent, voice model and pacing settings, manual testing, automated simulations and custom evaluations that score calls against business goals
Consent and trust Cloning requires filling out a legal agreement confirming you hold the rights or consent for the sample, and use is bound by Hume's Terms of Use and Ethical Guidelines SOC 2, HIPAA, PCI DSS, GDPR and ISO 27001, with encryption, audit logs and region-based hosting. Per-agent controls decide whether recordings and transcripts are kept at all, cap retention at 30 days, and redact personal data from transcripts, webhook payloads and logs
MCP-ready No stated Yes
Deployment Cloud (SaaS), Browser-based Cloud (SaaS), Browser-based
Support Community forum Email helpdesk
Onboarding Documentation and knowledge base more entries Documentation and knowledge base, Personal consulting
Company size more entries Freelancers, Small and mid-sized, Enterprise Enterprise
Integrations Not stated HubSpot, Salesforce, Zapier, Cal.com, GoHighLevel, Twilio, Genesys, Avaya, Five9, Cisco, RingCentral

Compare more tools

Row where the values differ The small markers point at the lower number, the longer list or the stated feature. They describe the data, they are not a verdict.

The short version

Key Differences

  • Starting price Hume AI Free tier; paid from $3 / month Synthflow From $30,000 / year
  • Company size Hume AI Freelancers, Small and mid-sized, Enterprise Synthflow Enterprise
  • Support Hume AI Community forum Synthflow Email helpdesk
  • MCP-ready Hume AI No Synthflow Yes
  • Commercial use Hume AI Yes Synthflow Yes, under an enterprise contract

Every line is one datapoint from the table above, picked automatically. Nothing here is written text.

The trade-offs

Strengths and Limitations

Hume AI

Strengths

  • Expressive, emotionally aware speech
  • Voice cloning from about 15 seconds and voice design from text prompts
  • Low-latency streaming for real-time voice agents

Limitations

  • Voice design and acting instructions are English only or still in preview
  • Character and EVI-minute caps scale the monthly cost

Synthflow

Strengths

  • No-code Flow Designer with a multi-agent system, so a non-developer can build and change call flows
  • Connects to existing telephony and contact centre stacks over SIP, including Genesys, Avaya, Five9, Cisco and RingCentral
  • White-labelled deployments for partners reselling voice agents under their own brand
  • SOC 2, HIPAA, PCI DSS, GDPR and ISO 27001, with agent-level retention and PII redaction controls

Limitations

  • No self-serve or trial tier is published; the only listed plan is an enterprise contract from $30,000 per year
  • Pricing is scoped by sales, so the cost of a given call volume is not knowable from the website
  • Latency figures differ between the vendor's own pages, so the published number is not a specification to rely on
  • A cloned voice has to be created in a separate ElevenLabs account and imported, so it means a second subscription alongside Synthflow

Plans

Pricing

Hume AI

  • Free $0 10,000 TTS characters and 5 minutes of EVI per month.
  • Starter $3 / month 30,000 TTS characters and 40 minutes of EVI per month.
  • Creator $14 / month 140,000 TTS characters and 200 minutes of EVI per month; 50% off the first month.
  • Pro $70 / month 1M TTS characters and 1,200 minutes of EVI per month.
  • Scale $200 / month 3.3M TTS characters and 5,000 minutes of EVI per month.
  • Business $500 / month 10M TTS characters and 12,500 minutes of EVI per month.
  • Enterprise Not stated Custom pricing with unlimited usage.
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Synthflow

  • Enterprise $30,000 Per year, the stated starting point. Scoped around call volume, concurrency, telephony setup, integrations and security needs, and covers implementation, onboarding, testing, training, launch support and ongoing optimisation, with SLA and support terms set in the contract.
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What users say

Review Scores · opens after launch

Hume AI

Ease of use
Not rated yet
User interface
Not rated yet
Onboarding
Not rated yet
Support and service
Not rated yet
Value for money
Not rated yet
Features
Not rated yet

No reviews yet. Be the first to review this tool. Every review is checked for fairness before it appears, and the vendor cannot have one removed.

Synthflow

Ease of use
Not rated yet
User interface
Not rated yet
Onboarding
Not rated yet
Support and service
Not rated yet
Value for money
Not rated yet
Features
Not rated yet

No reviews yet. Be the first to review this tool. Every review is checked for fairness before it appears, and the vendor cannot have one removed.

Where this comes from

Where this comes from

Hume AI https://www.hume.ai · no check date recorded yet

Synthflow https://synthflow.ai · checked against the official source on 2026-09-13

This table lists factual criteria taken from information the vendors publish themselves. For how we put it together, see the methodology.