LISNR is an ultrasonic, inaudible technology;
a communication protocol that sends data over audio.

We use inaudible sound waves called Smart Tones™ to transmit information.

LISNR transmits customizable packets of data every second that can enable device connectivity everywhere. Most notable solutions are proximity data transmission, second-screen functionality, authentication and low-fi device to device connectivity on any LISNR enabled device.

LISNR Protocol

LISNR is a data over audio solution that utilizes ultrasonic audio called Smart Tones. There are three parts to each Smart Tone: the preamble, the header, and the payload. In order to decode the data present in the waveform, the audio is run through a program called hflat (high-frequency LISNR audio tone).

Devices in audible range run the tone through a filter to remove background noise. Once a preamble is detected the LISNR SDK moves on to decode the data. Our audio frequency range is~ 18.7 – 19.2 kHz.

The Preamble

The preamble announces the presence of a signal so that hflat knows it needs to start decoding data.

The Header

The header contains metadata about the payload which tells hflat how much data it should look for in the payload, as well as a check-sum for error correction purposes.

The Payload

The payload is the actual data-containing portion of the tone; it also contains a check-sum for further error correction.

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LISNR Portal
Technology Access


Software: C Library base with restful API depending on use

Specific components: SDKs, API, Developer Portal w/ CMS




Our Smart Tones have greatly improved audio tone efficiency and reliability over our competitors. Local Tone Generation, our newest feature, enables device to device communication, including Audio Mesh Networking. This opens the door for many devices to interact with each other on a wide scale without other forms of connectivity. LISNR is incredibly reliable, showing 100% connectivity in multi-environment tests.


LISNR’s technology is the only commercial-grade ultrasonic protocol that has been deployed globally. Our software base is built from a C-library with additional functionality wrapped into specific SDK’s and API’s depending on platform and use case. This allows for full functionality across all software platforms. We also have a full Customer Support team that can coach you through any execution or be your on site partner for a larger implementations.


LISNR-enabled devices can detect a Smart Tone as fast as .6 seconds, but can be adjusted based on use case. For more complex use cases, we can take as long as 3 seconds to ensure the best connection. LISNR enables offline authentication, single use tones combined with metadata and tokenization between devices to ensure a completely secure connection.


LISNR is incredibly efficient in CPU/battery usage when compared to other data transmission technologies. With limited hardware requirements (speaker or microphone) and no other data connectivity needed, LISNR is a turnkey solution for data transmission between devices. Our tones can be decoded and encoded directly from the device, so no connectivity is needed.