Hume AI Pricing & Developer Hub
Everything you need to know about Hume AI pricing in 2026: platform fees, serverless quotas, compute instance rates, and bill optimization strategies.
Empathic Voice Interface: Hume EVI Architecture & Emotion Modeling
Hume AI is an emotional intelligence research lab pioneering the Empathic Voice Interface (EVI). Unlike traditional voice APIs that generate flat, monotone speech, Hume EVI analyzes vocal acoustic prosody—detecting 48 distinct dimensions of human emotion (including confusion, excitement, frustration, and sarcasm) directly from the caller's pitch and tone in real time.
Hume EVI prices its full-duplex multimodal conversational interface on a metered per-minute basis: $0.09 per minute of active conversation, which bundles real-time speech recognition, empathic LLM reasoning, and expressive emotional speech synthesis into a unified low-latency WebSocket connection.
Hume AI API Rate Card (March 2026)
| Product Tier | Unit Cost Rate | Included Capabilities | Target Application |
|---|---|---|---|
| Empathic Voice Interface (EVI 2) | $0.090 / minute | STT + Emotion LLM + Expressive TTS | Therapy, customer support, sales coaching |
| Expression Measurement API | $0.005 / image or sec | Facial expression & vocal burst metrics | Market research & UX user testing |
| Custom Voice Tuning | Enterprise Tier | Custom emotional range alignment | Branded conversational characters |
Frequently Asked Questions
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Hume Empathic Voice Interface (EVI 2): Prosody Analysis & Emotion AI Economics
Hume AI leads the industry in empathic, emotion-aware conversational AI with its **Empathic Voice Interface (EVI 2)**. While standard voice pipelines decouple STT, text LLMs, and TTS into discrete stages, EVI 2 is a multimodal audio-to-audio foundation model trained directly on acoustic prosody (tone of voice, cadence, pitch, sighing, and hesitations). It detects 48 distinct emotional expressions in real time with end-to-end conversational turn-taking latency under **250 milliseconds**. Pricing is structured around active conversational minutes at **$0.075 per minute**.
Hume AI Production Rate Card & Modality Matrix
| Model Service | Primary Capability | Billing Unit | Unit Rate | Latency SLA |
|---|---|---|---|---|
| EVI 2 (Audio-to-Audio) | Empathic voice conversational agent | Active Call Minute | $0.075 / min | < 250ms round-trip |
| Prosody Expression Model | 48 vocal emotion scores (Vocal burst) | Audio Second | $0.005 / sec | Batch / Streaming |
| Facial Expression Model | 48 facial action unit emotion scores | Video Second | $0.010 / sec | Webcam stream |
| Custom Voice Fine-Tuning | Proprietary brand voice clone | One-time training | Enterprise quote | Dedicated hosting |
Hume EVI WebSocket Streaming Client (TypeScript)
import { HumeClient } from 'hume';
const client = new HumeClient({ apiKey: process.env.HUME_API_KEY });
// Connect to Empathic Voice Interface with live prosody emotion telemetry
const socket = await client.empathicVoice.chat.connect({
onMessage: (message) => {
if (message.type === 'user_message') {
console.log('Detected emotions:', message.models.prosody?.scores);
} else if (message.type === 'audio_output') {
playAudioBuffer(message.data);
}
}
});
Production SRE Guardrails
- Emotion Confidence Thresholding: When integrating EVI into telehealth or customer escalation workflows, establish strict confidence gates. If user frustration scores exceed 0.85 for more than two consecutive turns, the system should trigger an immediate graceful transfer to a human supervisor.
- Audio Compression Over Cellular: Transmit 16-bit PCM audio sampled at 16kHz encapsulated in linear Opus frames. Hume's WebSocket receiver optimizes prosody detection on uncompressed vocal harmonics, while Opus minimizes packet drops over mobile connections.
What makes EVI 2 fundamentally different from OpenAI Realtime API?
OpenAI Realtime focuses on conversational fluency and general knowledge. Hume EVI 2 is explicitly trained on vocal prosody and emotional expression, allowing the agent to detect sarcasm, distress, excitement, or hesitation in the user's voice and adapt its vocal tone accordingly.
How is Hume EVI priced compared to modular voice stacks?
Hume EVI costs $0.075 per minute, combining STT, prosody analysis, reasoning, and expressive TTS into a single unified rate. A modular stack costs ~$0.041/min but lacks real-time empathic vocal prosody adaptation.
Hume AI Empathic Voice Interface (EVI) Semantic Tone Modeling
Hume AI's Empathic Voice Interface (EVI) departs fundamentally from standard text-to-speech architectures by jointly modeling acoustic prosody alongside semantic token distributions. Traditional voice bots pipeline discrete STT, LLM, and TTS steps, losing critical paralinguistic nuances like pitch modulation, hesitations, breath cadence, and tonal inflection. Hume's multimodal transformer processes raw continuous PCM audio waveforms directly, extracting 48 distinct dimensions of emotional and expressive sentiment in real time. This bidirectional architecture enables instant conversational turn-taking, allowing users to interrupt the AI naturally without awkward multi-second latency buffers.
Hume WebSocket Audio Streaming & Buffer Congestion Management
Integrating Hume EVI into production web applications requires streaming 16 kHz or 24 kHz linear PCM audio chunks over low-latency WebSockets. The client application dispatches base64-encoded audio frames every 50 to 100 milliseconds. When network congestion degrades client bandwidth, Hume's edge ingress gateway buffers inbound frames and dynamically adjusts jitter-buffer sizing to prevent audio packet starvation. Client-side audio visualizers can bind directly to Hume's real-time emotion probability events to dynamically render reactive conversational avatars in the browser.
Frequently Asked Production & Architecture Questions
Q: How does Hume EVI capture subtle human emotional nuances compared to standard TTS?
A: Hume EVI jointly models acoustic prosody and semantic tokens across 48 distinct expressive sentiment dimensions, capturing pitch variations, breath cadence, and tonal inflections directly from continuous raw audio waveforms.
Q: What audio formats are recommended for streaming client audio to Hume's WebSocket API?
A: Web and mobile applications should stream linear 16 kHz or 24 kHz single-channel PCM audio chunks in 50-to-100-millisecond buffers to guarantee sub-150-millisecond speech turn-taking latency.