The silent buyer: How sound and AI agents will power invisible payments

The way we pay is changing. From cards to mobile wallets to smart wearables, each shift has made transactions more seamless. With AI evolving rapidly and taking the front seat, a deeper transformation is now unfolding. Today’s financial systems were designed for humans, not autonomous agents capable of executing payments on behalf of users or organisations. In this new model, AI agents and sound-based systems are making transactions so seamless; they often go unnoticed. The generative AI market in finance reflects this shift with projections indicating growth from 1.09 billion US dollars in 2023 to over 12 billion by 2033.

To support this emerging ecosystem, financial institutions are beginning to explore programmable spending limits, enabling agents to operate within precise user-defined boundaries. Equally critical is the rise of Know Your Agent frameworks, which mirror Know Your Customer principles to ensure that agents are both identifiable and authorised. Together, these advances mark the rise of the Silent Buyer.

From consumers to AI agents with autonomy

The Silent Buyer is not a person but an intelligent system acting on behalf of one. AI agents, embedded in devices like phones, vehicles, and appliances, are now beginning to make decisions and purchases independently. Trained in user preferences and behavioural data, these agents can manage recurring transactions every month.

Where voice assistants once reacted to prompts, modern agents will proactively anticipate needs and act in real time, not based on commands, but understanding.

Sound as a new payment interface

As visible interfaces fade, sound is emerging as a powerful, ambient transaction medium. Technologies using ultrasonic audio to transfer payment tokens are gaining ground. These sound-based systems enable secure data exchange across devices without the need for the internet or Bluetooth. In environments like busy retail stores, transit hubs, or drive-throughs, this sonic handshake allows for seamless, contactless transactions that feel almost magical in their invisibility.

The rise of proactive transactions

AI agents are evolving into autonomous financial actors, executing payments and managing micro-decisions. This changes the user’s role from being a direct participant to being a system designer, someone who sets the rules and watches the system act on their behalf.

Trust, transparency, and identity

When transactions happen silently, transparency and trust must speak louder. Ensuring intent, identity, and consent is paramount. Voice biometrics, contextual authentication, and secure authorisation layers will play a central role. Know Your Agent (KYA) protocols are stepping forth as a new layer of assurance. These protocols are systems that verify an AI agent’s identity and confirm it is authoriesd to make payments on a user’s behalf. With KYC, just like banks check the person's identity, KYA checks the AI agent's identity & its capabilities. Therefore, they aid in verifying that the entity transacting is indeed a sanctioned, accountable extension of a user.

Implications for businesses and brands

Brands must now rethink how they reach consumers in a world where screens and apps fade away. In the near future, products will increasingly be discovered and purchased by AI agents set up by users and not the users themselves. If your business and products are discoverable by AI, embedded in the evolving ecosystem, and built on context & relevance, then you are on the winning track.

Conclusion: Designing for the invisible future

The future of commerce is intelligent, transparent and is on-the-go. As AI agents and sound-based systems become primary players in payment flows, the most forward-thinking businesses will be those who learn to design what is not seen and who build a world powered by invisible trust.

Authored by Kumar Abhishek, Founder and CEO of ToneTag