Hume AI vs Sierra

Empathic Voice Interface (EVI) is Hume's real-time speech-to-speech voice AI API, described in Hume's docs as 'an advanced, real-time emotionally intelligent voice AI.' The product page markets it as a way to 'Build voice-first AI experiences that understand and respond to human emotions' and states it 'works seamlessly with Claude, GPT, Gemini, Grok, Kimi K2, Llama, and more' - layering voice on top of third-party language models rather than supplying its own. It is billed per conversation minute on Hume's public plans.

The Expression Measurement API measures emotional and vocal expression in speech, marketed as 'Measure expression in voice, offline or in real time.' Hume describes two endpoints on the one page: 'The Tagger API returns 600+ expression and voice dimensions from any audio, at scale. The Prosody API delivers real-time emotional expressions during live conversations.' Measured dimensions include emotion categories, speaking styles, vocal qualities such as pace, warmth and hesitation, and expression intensity with confidence scores.

The Human Feedback API sells human evaluation of voice and conversational AI as an API call, marketed as 'One API call. Real human ratings.' and 'Plug human evaluation into your pipeline. Audio in, structured results out.' It supports three study types - live conversations with AI models, single-sample audio ratings with custom questions, and side-by-side A/B comparisons - with Hume handling participant recruitment, quality control and fraud detection. Hume states it powers 'evaluation for Hume's own frontier voice models.'

Octave TTS is Hume's text-to-speech API, which Hume's documentation calls 'the first text-to-speech system built on LLM intelligence.' The marketing page positions it as 'Text-to-speech with emotional intelligence' that generates 'expressive, natural-sounding speech that conveys the full range of human emotion,' with SDKs for Python, TypeScript, .NET and Swift and streaming audio output. It is billed by characters on Hume's public self-serve plans.

Evaluation platform for voice agents: it builds evaluation suites from real-world use cases, simulates agent-to-agent and human-to-agent conversations against any voice model, and tracks regressions over time.

Data Solutions is Hume's licensed AI training-data offering, headlined 'Voice Training Data Built by Researchers, for Researchers' and described as 'Datasets for creating realistic voices across global languages, powering our own state-of-the-art models, and now available to power yours.' The catalogue spans voice datasets covering 50+ languages, 48+ emotions and 600+ voice descriptors, plus expression and multimodal datasets for facial expression, vocal bursts, speech prosody and text emotion. Hume also sells custom data collection with defined speakers and recording conditions, and API access for programmatic data refresh and generation.

Platform for building and running customer-facing agents that handle support conversations over chat and voice.

Supplies persistent customer context and behavioral signals to Sierra's conversational agents.