Hume AI vs Speechmatics

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.

Speechmatics' automatic speech recognition API transcribes audio into text in 55+ languages in either real-time streaming or batch mode, with speaker diarization, custom dictionary, translation and summarization options.

Generates a short summary of an audio file in the same API call that transcribes it, as paragraphs or bullets. It is a Speech Intelligence feature enabled by adding a config block to a batch Speech to Text job, not a product bought on its own.

Speechmatics' text-to-speech API generates streaming synthetic English speech from text with sub-150ms latency using four named voices (Sarah, Theo, Megan, Jack), aimed at real-time voice agent use.

Translates a transcript into other languages in the same API call that produces it, for files or live audio. It is a feature switched on inside a Speech to Text request rather than a separate product; the docs file it under Speech to Text and return the translations alongside the transcript.

Speechmatics' voice agent offering provides a real-time conversational speech API - including the Flow WebSocket endpoint that chains speech-to-text, an LLM, text-to-speech and function calling - plus a Python Voice SDK for turn detection and speaker management, and integrations with Vapi, LiveKit and Pipecat.