Building AI voice agents: Starter guide

Published on Mar 10, 2025
Building AI voice agents: Starter guide

2025 marks a significant shift in AI-driven automation with the emergence of Agentic AI—intelligent, autonomous systems capable of reasoning, goal-setting, and adaptive decision-making.

Unlike traditional AI models that react to predefined inputs, these next-generation generative agents dynamically process complex problems, making autonomous voice interactions more natural and contextually aware.

Industries such as finance, e-commerce, healthcare, and telecommunications are integrating AI voice agents to automate workflows, optimize user engagement, and enhance customer interactions. These systems handle account management, intelligent troubleshooting, personalized shopping experiences, and predictive customer support—significantly improving both operational efficiency and user satisfaction.

This introductory article explores key considerations for evaluating the technical feasibility, deployment challenges, and scalability strategies required to integrate and optimize AI voice agents in production environments. The reader is expected to have foundational understanding of distributed systems, API architectures, machine learning models, and AI-driven automation.

What are AI voice agents?

AI Voice Agents are virtual assistants designed to interpret, understand, and respond to human voice commands. They combine multiple AI methodologies, including large language models (LLMs), speech-to-text, and text-to-speech (TTS), to facilitate natural conversational interactions between users and machines.

Legacy voice assistants like Siri and Alexa were built on rule-based NLP systems, requiring users to conform to structured commands such as “Send a message to…” or “Play [song name]” to ensure successful execution. Their capabilities were limited by predefined intent recognition and deterministic decision trees.

Modern AI voice agents, however, leverage advancements in deep learning, LLMs, and reinforcement learning to process ambiguous inputs, detect user intent, and generate nuanced responses. These agents go beyond basic command execution, offering context-aware conversations, personalized recommendations, and real-time problem-solving—fundamentally shifting them from passive assistants to autonomous task handlers.

Evolution of AI voice agent architecture

The evolution of voice systems starts with interactive voice response (IVR) systems. These systems relied on rigid commands to route calls before customers spoke to a human representative. The traditional IVR systems relied on pre-recorded voice menus launched at the beginning of a call. Callers had to navigate these menus using the keypad or voice before being routed to the appropriate agent.

The introduction of automatic speech recognition (ASR) brought a major shift, enabling real-time transcription and improving understanding of accents, tone, and emotion, making voice AI more intuitive. It brought voice agents closer to natural conversations instead of restricting them to repetitive menu selections.

Traditionally, AI voice systems rely on a sequential pipeline architecture. In this setup, speech is first transcribed into text using a real-time speech-to-text (STT) model. The text is then processed by LLMs to generate a response and then converted back to speech using a TTS model. Each section represents a distinct encoder-decoder architecture, with multiple points where latency and accuracy must be optimized, with loss of non-textual context like tone and emotion to be accounted for. 

Diagram with foundational building blocks of the voice agents infra stack
AI voice agent go-to-stack. Source a16z


The stack is predicted to evolve with the emergence of speech-to-speech (STS) models, bypassing transcription and processing raw audio inputs directly. These systems enable more human-like interactions by recognizing multiple speakers and emotional cues. While the STT + LLM + TTS stack remains the standard for its production-grade stability, speech-native models are emerging as the future of conversational voice. 

Alongside OpenAI’s recently released Realtime API, which enables STS interactions via GPT-4o, several companies like Vapi, Kyutai, and Alibaba are actively pushing this paradigm forward, signalling a shift towards more natural, real-time voice agents.

How do AI voice agents work?

As explained above, AI voice agents use advanced techniques in NLP, ASR, and TTS to understand and respond to voice commands. Let’s explore how these systems operate through a practical example, illustrating each step in the process.

Technical diagram representing the various layers making up the voice agent stack

Speech input

Imagine a customer interacting with an AI voice agent at a grocery store's virtual assistant. They might say, "What time does the store close today?" This spoken input is the first step in the interaction, where the customer's voice is captured as an audio signal, ready for processing.

Speech processing pipeline

Once the audio is captured, it undergoes a speech-processing pipeline. 

This involves these stages:

  1. Preprocessing: The audio signal is cleaned and normalized to enhance clarity.
  2. Feature Extraction: Techniques such as the Mel Spectrogram are used to convert the audio into a visual representation. This representation highlights frequency changes over time, making the system's analysis easier.

Automatic speech recognition

The next step is Automatic Speech Recognition (ASR) or STT, transforming the audio signal into text. Modern ASR systems leverage deep learning models, such as Recurrent Neural Networks (RNNs), to accurately transcribe spoken words. 

The audio is first converted into a format suitable for analysis. It then moves to acoustic modeling, where the system identifies phonemes and words, utilizing advanced computational resources such as GPUs or TPUs to ensure high performance.

Technical diagram showing the speech processing pipeline in ASR

Natural language understanding 

Once the text is generated, it is sent to the natural language understanding (NLU) system. Here, the AI interprets the meaning behind the words. 

For example, from the input, "What time does the store close today?", the NLU identifies the intent as "find store closing time" and extracts relevant details, such as the store's location.

Dialog management and state handling

The AI voice agent must maintain context throughout the conversation. This is achieved through dialog management and state handling, which allows the system to track the conversation's flow and manage different states over time. 

For example, if the customer follows up with, "What about the pharmacy hours?", the system understands the context and can provide relevant information without needing to repeat previous details.

Processing and decision-making

In this step, the AI voice agent determines the appropriate action based on the analysis of the input data.

This process is enhanced by Retrieval-Augmented Generation (RAG), which enables the agent to access external knowledge sources in real-time. 

For instance, when a customer asks, "What time does the grocery store close today?", the system retrieves the latest operational hours from the store's database, ensuring accurate and timely responses.

Response generation

After processing the request, the system generates a response using an LLM to ensure the reply is clear and professional.

For instance, the system might respond, "The store closes at 9 PM on weekdays." 

Text-to-speech

The text-based reply is then converted into speech through a TTS system, which synthesizes the response to sound natural.

Voice output

Finally, the synthesized speech is played back to the user through the device’s speaker, completing the interaction. 

The customer hears, "The store closes at 9 PM today," providing a satisfying response to their inquiry.

Key skills for agentic AI implementation

Building AI voice agents requires more than just coding expertise. Let's explore the essential skills that enable organizations to deploy and maintain robust AI voice systems.

Understanding AI guardrails

Expertise Level: Advanced

AI models must deliver results based on high-quality, relevant data that aligns with user prompts. Professionals need expertise sourcing and integrating data from multiple platforms to ensure it’s up-to-date and applicable. Knowledge of data streaming technologies like Apache Kafka and Apache Flink is essential for connecting data sources and enabling efficient communication with AI models. By building robust data pipelines, ML engineers and AI architects can ensure accurate, contextually appropriate responses grounded in reliable information.

Preventing data leakage

Expertise Level: Advanced

Expertise in data leakage prevention is vital to protect privacy and security, especially when processing sensitive information. For example, data shared with an LLM can become embedded in it. Security threats, such as prompt injection attacks, can exploit this vulnerability by attempting to extract proprietary information from the model.

To reduce the risk of data exposure, a containerization approach isolates data within defined boundaries, limiting access. Additionally, anonymization strategies, such as stripping Personally Identifiable Information (PII) from prompts, help minimize the risk of unintended data leakage.

Effective prompt engineering

Expertise Level: Intermediate

Strong prompt engineering is fundamental for implementing agentic AI effectively. This is crucial in tailoring AI agents to specific tasks, ensuring they operate efficiently and align with business objectives. Expertise in this area allows developers to create prompts in an industry-specific context, particularly in complex fields like finance or medicine.

To achieve optimal performance, companies also need proficiency in selecting the right models, as the choice of model significantly impacts prompt performance. More advanced models, such as GPT-4, deliver consistently better results than smaller models like Llama 7B. Furthermore, techniques such as few-shot prompting and system prompts can enhance model performance, especially for verticalized agents.

Optimizing API interactions 

Expertise Level: Intermediate

To successfully implement agentic AI, companies need professionals with strong expertise in managing secure and efficient API interactions. These experts must prioritize the integrity and functionality of systems by safeguarding APIs from misuse. This involves implementing secure authentication methods, monitoring API usage for suspicious activity, and establishing clear governance practices.

Auto-scaling techniques

Expertise Level: Advanced

Companies without auto-scaling expertise often have rigid agentic AI systems, limited to specific tasks and hindered by management overhead. 

Therefore, auto-scaling knowledge is essential to plan and implement these systems effectively across the enterprise. This would ensure that the right agent performs the right job in tandem with other agents and provides enterprise-level benefits.

Managing GPU resources

Expertise Level: Intermediate

Effective GPU management is crucial for deploying agentic AI. It ensures the smooth processing of tasks like real-time data analysis or large-scale AI models.

  • For beginners and small projects: GPUs like the Nvidia GTX 1660 or RTX 3050 and AMD Radeon RX 6700 XT are great for image classifiers and smaller neural networks.
  • Mid-level AI workloads: The Nvidia RTX 3060/4060 and AMD MI100 are ideal for fine-tuning pre-trained models like BERT or GPT-2.
  • Heavy-duty AI applications: For larger models and intensive tasks, GPUs like the Nvidia A100 or H100 and AMD Instinct MI250 are essential to handle large LLMs, multi-modal AI models, and high-demand production workloads.

Leveraging cloud infrastructure

Expertise Level: Intermediate

Companies need a solid understanding of cloud infrastructure to choose the right cloud AI services and maximize AI benefits. Knowledge of platforms like Google Cloud's Vertex AI helps organizations develop and deploy AI models efficiently, streamlining operations and reducing costs. This expertise enables innovation and competitiveness in a fast-evolving digital landscape.

Best practices for building an AI voice agent

AI voice agents rely on real-time streaming for smooth and responsive interactions. Effective session management, error handling, and strong security practices ensure they perform reliably and meet user expectations. Here’s a list of essential best practices – with a summary checklist at the end of this section.

1. Designing an effective AI system

Designing an effective AI voice agent requires careful planning around model training, feedback loops, and risk mitigation. Let’s examine the essential considerations for creating a reliable and well-structured AI system.

Multidisciplinary approach

Successful agentic AI requires a well-trained, critical-thinking model based on real-world data. It must incorporate detailed information on goals, plans, actions, results, and continuous feedback. As a result, it is essential to assemble a team of experts from various domains, including IT specialists, data scientists, and professionals who have an in-depth understanding of the business processes.

Monitoring AI activities

Establishing clear guidelines ensures AI functions within safe parameters, preventing errors or unintended actions. Real-time monitoring provides continuous oversight while allowing AI autonomy. This enables human intervention when needed, ensuring smooth operations and minimizing risks.

Error recovery mechanisms

AI voice agents must use context monitoring and feedback loops like reinforcement learning to identify user dissatisfaction or repeated corrections. These insights refine interactions over time, improving accuracy and responsiveness.

2. Optimizing real-time performance

Optimizing system performance means implementing efficient data processing methods, reducing latency, and handling concurrent interactions effectively. Let’s break down the key technologies that make this possible.

WebSocket integration for continuous communication

WebSockets enable uninterrupted, bidirectional communication, eliminating the need to reopen connections. This enhances responsiveness, accessibility, and the overall user experience.

Concurrent session handling

Managing multiple AI interactions efficiently is critical in high-demand environments like call centers. A robust API for real-time audio processing ensures minimal latency and quick response times, even during peak traffic.

Microservices architecture

Adopting a microservices framework can provide several benefits, including improved modularity, scalability, and resilience. Independent services that handle tasks like speech recognition or TTS conversion can scale individually based on demand, optimize resource use, and ensure the continuous operation of the AI system.

Load balancing

Traditional load-balancing methods struggle with AI workloads due to their dynamic and resource-intensive nature. AI-aware load balancers address this by efficiently distributing traffic based on real-time metrics, helping businesses optimize system performance during traffic spikes. AI tasks like content generation often take time, but streaming-specific load balancers allocate traffic efficiently, preventing system overload and ensuring faster processing.

3. Ensuring secure and reliable AI operations

Implementing strong security measures ensures that AI voice agents remain trustworthy and resilient against cyber threats.

Securing foundations

To protect sensitive interactions, businesses must implement multi-layered security protocols like Role-Based Access Control (RBAC). This ensures that only authorized employees can access customer data, preventing unauthorized usage. Similarly, Intrusion Detection Systems (IDS) continuously monitor activity for suspicious patterns, allowing quick responses to potential attacks.

Privacy compliance

Voice agents can ensure regulatory compliance by adopting strategies for data protection and transparency. For example, companies operating in the EU under GDPR or in California under CCPA can implement mechanisms for customer consent and data deletion requests, ensuring that they remain compliant with privacy laws.

Data encryption

Using end-to-end encryption ensures that conversations between customers and the voicebot stay secure during transit. By combining this with Transport Layer Security (TLS), we can have a robust framework that prevents eavesdropping or tampering, even in high-risk industries like finance and healthcare.

Robust data retention policies

Organizations must establish clear data retention policies that define how long various data types are retained. A best practice would be to set retention timelines based on compliance requirements and business objectives. This approach not only aids regulatory compliance but also ensures unnecessary data is securely deleted, reducing long-term risk exposure.

Comprehensive security frameworks

Establishing comprehensive security frameworks is essential for Agentic AI to function effectively and responsibly. These frameworks address critical challenges like transparency, data protection, and compliance.

Ensuring secure handling of critical data

Handling sensitive data demands stringent security measures. Encrypting data alone isn't sufficient, organizations should also apply role-based access controls to restrict who can view or manipulate sensitive information.

Partner with SOC 2 compliant firms

When considering technology partners, prioritize those with SOC 2 compliance. This certification demonstrates that a company maintains high standards for data security and privacy.

4. Optimizing infrastructure and connectivity

To optimize the performance and reliability of AI agents, we can leverage edge computing and implement a multi-cloud strategy to enhance infrastructure and connectivity.

Connectivity considerations

The performance of voice AI agents can be significantly impacted by network connectivity. For optimal functioning, minimizing latency is key. Edge computing allows data processing to occur near the source and ensures quick responses and a seamless experience even with high user traffic. 

Use multiple cloud providers

Avoiding reliance on a single cloud provider can prevent single points of failure. By distributing services across multiple providers, businesses can improve reliability and minimize risks associated with potential outages or vulnerabilities.

5. Specialized administrative systems 

Establishing specialized administrative systems and governance frameworks can streamline the management of agentic AI workflows. By using workflow orchestration and monitoring tools, businesses can avoid system failures and ensure high reliability in AI operations.

Microsoft has developed Copilot Studio, an environment enabling businesses to create tailored agents for various workflows, making managing and orchestrating AI processes more straightforward. 

Bandwidth management is critical to prevent audio interruptions. Implementing Quality of Service (QoS) protocols can prioritize voice traffic, helping to maintain a smooth experience, similar to what we find in a Voice-over-IP (VoIP) hosted call center.

Checklist for best practices in building an AI voice agent

Use cases of AI voice agents

AI voice agents are transforming various industries by providing scalable, context-aware automation that enhances efficiency and user experience. Here are some of the most exciting applications of this technology today.

Contact centers

In contact centers and customer support, AI voice agents automate routine inquiries, reducing wait times and improving resolution rates. They assist with troubleshooting, transaction support, and service requests while optimizing call routing by identifying user intent and directing inquiries to the appropriate department or human agent. Advanced implementations incorporate real-time sentiment analysis, allowing businesses to assess customer emotions and adjust responses dynamically.

E-commerce

For e-commerce and retail, AI-powered voice agents enhance voice-assisted shopping experiences by enabling seamless product searches, personalized recommendations, and order management through natural voice interactions. They allow users to place, modify, or track orders without navigating complex interfaces, improving accessibility and convenience for online shoppers.

Healthcare

In healthcare and telemedicine, AI voice agents streamline administrative tasks such as appointment scheduling, patient reminders, and medical information dissemination. They support multilingual interactions, making healthcare services more accessible to diverse populations, including patients with disabilities. By automating routine patient interactions, voice AI helps reduce the burden on healthcare professionals while improving patient engagement.

Finance

Within finance and compliance, AI voice agents assist with customer service, fraud detection, and regulatory oversight. Banks and financial institutions deploy AI-powered assistants to help users manage transactions, check balances, and access financial services via secure voice authentication. In compliance-focused applications, AI-driven systems analyze trader communications to detect potential misconduct, ensuring adherence to regulatory standards.

Future of AI voice agents

AI voice agents are on the brink of a transformative shift, with advancements in multimodal processing, emotion recognition, and contextual understanding set to redefine human-technology interactions.

1. Multimodal processing

One of the standout advancements is multimodal processing, which allows voice agents to seamlessly integrate and comprehend various input types, including text, audio, and even visual data. Google’s recent upgrades to its AI models underscore this trend, as they enable assistants to process both spoken requests and visual inputs, allowing for richer interactions. 

For instance, an AI voice agent could now recognize a user’s request to find a particular product while also pulling up relevant images for that item, providing a holistic search experience.

Predicted evolution of voice AI agents on a flow diagram

2. Emotion recognition

Emotion recognition technology is rapidly evolving, enabling voice agents to interpret the emotional state of users through vocal cues. Companies like NICE are spearheading the charge in emotion detection within voice AI, helping organizations tailor their responses based on user sentiment. 

Imagine a customer service agent that can assess a caller's frustration through their voice and route the call to a human agent more equipped to handle distressing situations. This enhances customer satisfaction and builds trust between consumers and brands.

3. Context handling

Enhanced context handling is another vital area of development in voice AI. Contextual understanding enables these agents to maintain conversation flows without losing track of the dialogue. 

This means that if you ask your virtual assistant about a flight and follow up with a question regarding hotel bookings, it can seamlessly transition between topics without needing you to restate details. This capability allows users to engage in more natural conversations with technology, bridging the gap between human interaction and voice AI.

4. Cross-platform consistency

Cross-platform consistency is essential for organizations aiming for seamless user experiences. Microsoft has exemplified this trend with its voice technologies across applications like Teams and Office 365. Such integration enables users to access advanced voice functionalities regardless of their platform, whether managing schedules in Outlook or conducting video calls in Teams.

Final remarks

AI voice agents are revolutionizing human-machine interactions by replacing rigid commands with dynamic, human-like conversations using STS architectures, RAG, and multimodal processing, ensuring accuracy, security, and scalability.

Gladia empowers businesses to create enterprise-scale voice-first platforms and agents with real-time audio processing, multilingual support, and advanced analytics. 

Try Gladia’s API for free, or book a demo to explore its features and pricing.

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