How DialNexa Voice AI Works

Learn how DialNexa voice AI turns caller audio into transcription, model responses, synthesized speech, actions, and Call History evidence.

DialNexa Voice AI works by moving each call through a loop: receive audio, transcribe speech, decide the next response with the configured agent version, optionally call tools, synthesize speech, and store the result in Call History.

If you can follow the loop, you can debug most calls without guessing. Guessing is dramatic, but logs are cheaper.

How DialNexa Voice AI Works During A Call

1. Caller audio arrives

   Audio enters through a Plivo number, SIP trunk, web call, batch call, workflow call node, API call, or test call.

2. The transcriber listens

   Deepgram or Soniox converts speech into text. The transcript is later shown in Call History as realtime and, where available, post-call text.

3. The agent decides

   The published agent version supplies prompt, system prompt, language, LLM model, dynamic variables, functions, and safety settings.

4. Tools may run

   Functions and integrations can end a call, book a calendar event, call an API, send a WhatsApp message, send an email, or trigger another configured action.

5. The voice speaks

   ElevenLabs or Cartesia synthesizes the response. Audio Cache can reduce latency for repeated exact phrases.

6. Evidence is saved

   Call History receives status, summary, transcript, recording URL, post-call analysis, transfer details, Audio Cache data, and metadata.

Provider Work At Each Runtime Layer

Layer	Provider choices	Why users should care
Audio route	Plivo, SIP trunking, web call.	Changes number ownership, audio quality, routing, and whether phone network issues are involved.
Speech to text	Deepgram or Soniox.	Changes transcript accuracy, language fit, turn timing, and Response Eagerness support.
Reasoning	OpenAI, Google, or Groq. Speech-to-Speech agents use a realtime model (OpenAI gpt-realtime-2 or Gemini 3.1 Flash Live) that replaces the separate transcriber and voice.	Changes instruction following, latency, structured behavior, and fallback strategy.
Text to speech	ElevenLabs or Cartesia.	Changes voice identity, pronunciation, streaming behavior, and cache compatibility.
External actions	Wati, Resend, Custom Functions, webhooks.	Changes what the call or workflow can do outside DialNexa.

Runtime Input Versus Saved Evidence

Do not confuse what starts a call with what proves it happened.

Layer	Examples	Where reviewed
Input	Recipient number, metadata, dynamic variables, workflow lead variables, selected outbound number.	Batch setup, workflow lead, API request, or test call modal.
Agent version	Prompt, model, voice, transcriber, welcome mode, functions, post-call fields, fallback settings.	Agent builder and version history.
Call result	Status, duration, sentiment, end reason, transcript, summary, recording, extracted fields.	Call History and call detail page.

What Can Change A Reply

The same caller sentence can lead to different behavior when these settings change.

Prompt and system prompt

Instruction wording decides goal, boundaries, escalation rules, and acceptable answers.

Dynamic variables

Caller-specific values can change greeting, eligibility, due date, location, or transfer destination.

Functions

Tools add actions the model can call during the conversation.

LLM and temperature

Model choice and temperature affect reasoning style and consistency.

Debug By Layer

Audio sounds bad

Check recording quality, phone path, SIP trunk behavior, web microphone, and Denoising Mode.

Transcript is wrong

Check language, Deepgram or Soniox selection, background noise, and whether the caller spoke over the agent.

Transcript is right but answer is wrong

Check prompt, dynamic variables, functions, knowledge source, model family, and temperature.

Answer is right but late

Check Response Eagerness, Audio Cache, fallback LLM, function latency, and integration action placement.

Related Reading

Speech To Text

Understand Deepgram and Soniox behavior.

LLM Behavior

Tune reasoning and fallback behavior.

Provider Selection Guide

Choose the complete provider stack.

Text To Speech

Choose ElevenLabs or Cartesia.

Integrations

Understand Wati, Resend, and workflow actions.