Voice AI Development
Conversations that answer in under 700 milliseconds, handle interruptions, and hand to a person the moment they should.
Plan a voice pilot ↗
What is voice AI development?
Voice AI turns a phone call or an in-app conversation into a working exchange: speech to text, a decision about what to say, text back to speech — fast enough that the caller doesn’t start talking over it. The hard constraint is the round trip, not the intelligence.
A useful budget is under 700ms from the caller finishing a word to hearing the first syllable back, and that has to cover transcription, any lookup, generation and synthesis. It shapes every choice — streaming everything, keeping prompts short, pre-warming connections — and it’s why the second thing we build, right after the happy path, is an obvious and fast route to a person.
What a voice build includes
A latency budget
Milliseconds allocated per hop — transcription, decision, synthesis, network — and measured in production, so any regression has a suspect.
Domain vocabulary
Product names, postcodes, drug names and reference formats biased into the recogniser, because generic speech-to-text mangles exactly the words that matter.
Barge-in and turn-taking
The caller can interrupt and be heard immediately, with endpointing tuned so a thinking pause isn’t treated as the end of a sentence.
Human handoff
A transfer path that carries context across, triggered by frustration, silence, repetition or a plain request — never a dead end.
Telephony integration
Numbers, SIP or WebRTC into your existing call flow, so voice AI takes one queue rather than replacing your phone system.
Consent and transcripts
Recording notices, retention rules and searchable transcripts alongside the audio, so calls can be reviewed, coached from and challenged.
How a voice project runs
Set the budget
We agree the latency target and the single call type to start with, then design backwards from the round trip rather than forwards from the prompt.
Build the vocabulary
Real recordings and real terminology, so accents, names and reference numbers get tested before launch instead of by your customers.
Prototype one flow
One call type end to end on a real line, with the human handoff working before the conversation is anywhere near polished.
Tune on recordings
We listen to failed calls weekly, fix endpointing, prompts and transfer triggers, and re-measure latency at p95 rather than on average.
Pilot with a kill switch
A slice of live traffic, an instant route back to your existing IVR or team, and containment measured against how those calls went before.
Voice AI Development FAQ
One call type on a live line is typically $20k to $55k to build. Per-minute speech and model costs usually land between $0.06 and $0.20 a minute depending on vendors, and we model that number during scoping so the unit economics are visible early.
The tools we build with
Every pick is judged against the latency budget first, because a smarter answer that lands a second late feels worse to a caller than a plain one that arrives instantly.
Speech & language
OpenAI
Anthropic
Hugging Face
OllamaRealtime transport
Socket.IO
Node.js
RedisServices
Python
FastAPI
TypeScript
PostgreSQLRun & watch
Docker
Cloudflare
AWS
Grafana
SentryRelated work
Related reading
Got a call type worth automating?
Tell us the call and the monthly volume. We’ll come back with a latency budget, a per-minute cost and a pilot scope that includes the kill switch.