The rise of conversational AI has fueled rapid advancements in voice technology, with synthetic voice agents becoming central to customer interactions, virtual assistants, and enterprise automation. Building these systems requires more than just speech synthesis, it depends on scalable infrastructure that can handle natural language processing, real-time responses, and integration with business workflows.
In this article, we highlight the top synthetic voice agent infrastructure developers, exploring companies that provide the platforms, tools, and frameworks powering the next generation of voice-driven experiences.
Best Synthetic Voice Agent Infrastructure Developers
Impekable is a full-service, end-to-end digital product consultancy with deep expertise across product strategy, design, and development, scaling from idea through launch and beyond. Their technology stack allows them to build intelligent, scalable voice and communication platforms, integrating real-time voice agents with rich UX and reliable cloud infrastructure.
When it comes to synthetic voice agent infrastructure, Impekable’s services are built around delivering high fidelity conversational experiences 24/7 for customer service and other touchpoints. They offer custom AI development that handles the full voice pipeline, speech recognition, natural language understanding, dialogue management, and expressive text-to-speech, enabling businesses to reduce operational costs, increase responsiveness, and deliver more natural interactions with users.
- Services and expertise: AI development, AI voice agents, AI agent development, app modernization, product strategy, customer experience & product development, SaaS application development
- Location: offices in San Francisco (HQ), San Jose, Sydney
- Team size: 11-50 employees
- Portfolio: MONAI, Netgear ARLO, Pentair, Panasonic Beta, Nike
Replicant is a conversational AI platform focused on automating customer service across both voice and digital channels. As one of the agencies offering infrastructure for synthetic voice agents, they aim for interactions that “listen, understand, and get things done” without rigid scripts or long wait times. Their platform combines voice-first automation with conversation intelligence, helping clients reduce load on human agents, elevate CX (customer experience), and resolve routine customer requests automatically.
What also sets Replicant apart among the best synthetic voice agent infrastructure developers is their track record with real-scale deployments. They’ve handled hundreds of millions of minutes of live conversations, apply robust NLP (natural language processing) & speech recognition, integrate with existing contact-center systems, and support voice/resolution tasks that go beyond simple FAQs, such as call routing, authentication, billing & payments.
- Services and expertise: Conversational AI, voice and chat agents, conversation automation, conversation intelligence, outbound calling, appointments and scheduling, routing and authentication, account management, billing and payments
- Location: offices in San Francisco
- Team size: 51-200 employees
- Portfolio: Sunrun, DoorDash, Love’s Travel Stops, NJ TRANSIT, ECSI, Canadian Automobile Association (CAA), Southwest Medical Imaging (SMIL), CorVel
ElevenLabs is an AI audio research and deployment company known for its advanced speech synthesis, voice cloning, and conversational AI tools. They aim to make content universally accessible in any language and any voice, with models that generate realistic, versatile, and contextually-aware speech across 30-32+ languages.
As one of the top companies developing synthetic voice agent infrastructure, ElevenLabs offers a platform for building AI voice agents that listen, understand, and act in real time. Their “AI voice agents” service includes features like CRM/workflow integration, always-on availability, multi-language support, and full configurability. Their tools are designed for low latency so voice conversations feel natural, and they support both inbound and outbound voice interactions.
- Services and expertise: Text-to-speech (TTS), voice cloning, conversational AI voice agents, multilingual speech models, real-time API integrations, expressive/emotional speech, enterprise-grade security
- Location: London (UK) / British-Polish origin, with operations in US and internationally
- Team size: 300-350 employees
- Portfolio: Publishers (e.g. The New Yorker, The Washington Post, The Atlantic), gaming studios such as Paradox Interactive, content creators, audiobook producers, call center and customer support automations
PolyAI is one of the top synthetic voice agent infrastructure developers specializing in enterprise voice assistants that can hold natural, human-like conversations. Their technology allows brands to build voice agents that understand customers in multiple languages, integrate deeply with contact-center tools, and continuously improve via analytics and refinement of their models.
They have demonstrated real-scale value: for example, their deployment with Pacific Gas & Electric (PG&E) generated major labor savings, improved customer satisfaction, and managed high call volumes during outages, showing how their infrastructure can handle both normal and high-stress conditions.
- Services and expertise: Enterprise voice assistants, multilingual spoken conversation, speech recognition + large language models, integrations with CRMs/telephony, agentic AI for voice + chat + SMS, real-time analytics & conversational journey management
- Location: London, UK (global operations)
- Team size: 300+ employees
- Portfolio: Pacific Gas & Electric (PG&E), Unicredit, Caesars Entertainment, Marriott, FedEx, Metro Bank, Whitbread, Simplyhealth
Yellow.ai is among the best synthetic voice agent infrastructure developers, offering enterprises voice-AI agents that can manage large volumes of customer interactions with natural, context-aware conversations. Their “VoiceX” platform is designed to replace rigid voice bots by supporting voice AI that listens, speaks, understands past conversations across channels, and hands off to humans when needed, all while integrating with enterprise systems.
They also emphasize ease-of-deployment, multilingual support, and strong analytics; with over 135 languages supported, pre-built integrations with major contact centre / CRM tools, and real-time feedback & insights to refine the voice agent performance. These capabilities help companies reduce costs, improve CSAT (customer satisfaction), and shorten time to value when implementing synthetic voice agent infrastructure.
- Services and expertise: Voice AI / Voice automation (VoiceX), multilingual voice agents, DynamicNLP, LLM-powered voice agents, pre-built integrations with CRMs / telephony, real-time analytics & reporting, custom response via TTS + SSML, inbound & outbound voice flows
- Location: Headquartered in San Mateo, California, USA; global operations.
- Team size: 650+ employees
- Portfolio: Sony, Flipkart, Hyundai, Domino’s Pizza, Waste Connections, Ferrellgas, Randstad, Lion Parcel
Vapi is a developer-friendly platform that empowers teams to build and run AI voice agents at scale, positioning itself among the top companies developing synthetic voice agent infrastructure. Its API-first design lets businesses bring their own transcription, language model, and speech tools, or use Vapi’s defaults, enabling flexible, tailored pipelines for call answering, appointment scheduling, lead qualification, or outbound outreach. Their system supports sub-500ms latency and enterprise-grade reliability, making it a strong choice for phone-based voice AI.
Vapi’s emphasis on configurability and integration makes it stand out: teams can plug into over 40 apps, like OpenAI’s GPT, Twilio telephony, Zendesk, HubSpot, and Salesforce, streamlining deployment across CRM and support workflows. The platform also provides tools for testing voice agents before launch, monitoring call performance, and refining conversational flows, making Vapi suitable for technical teams building synthetic voice agent infrastructure with a high degree of control.
- Services and expertise: Flexible voice AI platform, inbound and outbound voice call agents, “bring your own model” transcription / LLM / TTS, API native voice workflows, tool-calling, automated testing, A/B experimentation, configuration or model customization
- Location: San Francisco, California, USA (YC-backed)
- Team size: under 50 employees
- Portfolio: FleetWorks, Unity, NY Life, Intuit, Instawork, Housecall Pro, Cherry, GoHealth, PolicyBind, Hotel Planner
Synthflow offers an enterprise-ready AI voice agent platform for automating phone calls. They support both inbound and outbound voice agents, letting businesses build, launch, and scale human-like voice agents quickly using no-code tools or APIs. They emphasize fast deployment (often under three weeks), multiple languages, integrations with existing tools (like CRM systems, call routing, dashboards), and performance metrics like low latency and high uptime.
Use cases for Synthflow span customer support, appointment scheduling, IVR (interactive voice response), lead qualification, receptionist/concierge style tasks, data collection, and more. They provide prebuilt templates, visual flow designers, monitoring and testing tools, and allow call logic customization (handoffs to humans, SMS follow-ups, voicemail detection, etc.). Industries served include healthcare, BPO / contact centers, real estate, e-commerce, and sales.
- Services and expertise: No-code voice agents, inbound/outbound call automation, multilingual support, visual flow designer, integration (CRM, telephony, APIs), templates, monitoring/testing of call flows, custom actions, SMS & follow-ups, live & scheduled appointments, lead qualification, IVR style routing
- Location: operating worldwide
- Team size: 11-50 employees
- Portfolio: Medbelle (healthcare scheduling), Smartcat (lead qualification & outbound costs cut), Peak Demand (data collection / public sector), US & LATAM BPO operator (40+ agents handling 600K+ calls per month) among others
SoundHound AI builds conversational and voice-first AI agents that listen, reason, and act across voice, chat, and device workflows. Their platform includes products like Amelia for enterprise agents, Smart Answering for phone call handling, Voice Commerce, Dynamic Drive-Thru, Edge & Cloud Connectivity, Employee Assist, and more. They serve industries such as automotive (in-vehicle), restaurants, smart devices, healthcare, finance, telecommunications, travel & hospitality.
They also provide a developer platform (Houndify), custom voice AI solutions, and utilities like wake-word detection. Use-cases include customer service automation, smart ordering, self-service voice assistants, and conversational user experiences embedded in both physical devices and apps. Their tools emphasize scalability, multilingual deployment, and customizing voice experiences per brand.
- Services and expertise: conversational AI agents, voice assistants / voice-first interaction, voice commerce, custom voice AI, wake-word, edge & cloud connectivity, smart ordering, dynamic drive-thru, employee assist, contact-center voice answering, automotive voice/chat integration
- Location: Santa Clara, California, USA
- Team size: 501k-1k employees
- Portfolio: Stellantis; White Castle; Pandora; BNP Paribas Securities Services; Telefónica; Teva Pharmaceuticals
iFLYTEK is a longstanding AI company specializing in speech recognition, speech synthesis, machine translation, and human-machine interaction, among others. If you choose to hire synthetic voice agent infrastructure developers, iFLYTEK is one of the major options, especially for projects needing high accuracy in voice recognition, support for many dialects, and robust natural language processing. Their voice recognition accuracy has surpassed 98%, and they support a wide variety of spoken Chinese dialects.
They also operate cloud/open-platforms that connect large numbers of devices and developers, offering tools for transcription, translation, AI voice assessment, and real-time voice processing. Their infrastructure has been applied in sectors such as education, legal / judiciary, marketing, and smart devices. When working with clients who need comprehensive voice agent support, from backend models, streaming and device integration, to deployment at scale, iFLYTEK is often considered.
- Services and expertise: Speech recognition, speech synthesis, translation, NLP, voice assessment, real-time voice & transcription platforms, open platform ecosystem, AIUI human-machine interaction interface
- Location: Hefei, Anhui, China
- Team size: Not specified
- Portfolio: Huawei (smart device integration), China judicial system (courts / prosecutors), educational institutions (language testing / assessment), governments, many developers using their voice cloud platforms, connected devices ecosystem
Twilio provides a cloud communications platform that includes programmable voice, messaging, video, and more. Among its voice-related offerings are Voice API (for calls, IVR, speech recognition, call recording, etc.), Voice SDKs, and features like Conversational AI and Conversational Intelligence, enabling businesses to build richer, more automated, and more responsive customer interaction systems.
They also offer ConversationRelay, a service for streaming voice in real time to/from an LLM (or other AI backend), so that spoken input is transcribed and responded to via speech-synthesis, letting developers build voice agents with lower overhead. There are tutorials showing how to combine Twilio Voice + ConversationRelay + external LLMs like OpenAI or Mistral to implement conversational voice agents.
- Services and expertise: Programmable Voice API (IVR, speech recognition, call routing, call recording, speech-to-text, text-to-speech), ConversationRelay, Conversational AI tools, Voice SDKs, virtual agent integration (e.g. with Dialogflow)
- Location: office in San Francisco, California
- Team size: Not specified
- Portfolio: Marks & Spencer (AI-powered IVR), St. Luke’s University Health Network, Trulia, Zendesk among others using their Voice API and related services
Conclusion
As synthetic voice technology continues to expand across industries, businesses are looking for reliable partners who can provide scalable, secure, and flexible platforms. Choosing the best synthetic voice agent infrastructure development agencies means gaining access to advanced tools, streamlined integrations, and expertise that can support both experimental projects and enterprise-level deployments. These agencies play a vital role in shaping how companies deliver seamless, voice-driven customer experiences in the years ahead.
If you want to feature your company developing synthetic voice agent infrastructure on this list, email us or submit a form in the Top Choices section. After a thorough assessment, we’ll decide whether it’s a valuable addition.
