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

LISNR transmits customizable packets of data every second that can enable device connectivity everywhere. We use inaudible sound waves called Smart Tones™ to transmit information. Most notable solutions are proximity data transmission, second-screen functionality, authentication and low-fi device to device connectivity on any LISNR enabled device.

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How it Works

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.


Software: C Library base with restful API depending on use. Specific components: SDKs, API, Developer Portal w/ CMS.
LISNR is compatible with all operating systems.





Our Smart Tones have best in class performance metrics in reliability & data throughput. 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 continues to innovate successfully releasing full commercial grade enhancements that average 2-3X data throughput and 10X reliability increases every 6 months since 2013.


LISNR’s technology is a commercial-grade globally deployed ultrasonic protocol. 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 is completely customizable depending on use case and platform. LISNR has the ability to even enable custom profiling that can customize data throughput, reliability, detection time and even range. Custom Smart Tone profiling allows LISNR optimize performance per use case & environment. All Smart Tones are tied to specific API keys alongside tokenization, single use and advanced encryption to create a secure data exchange.


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 locally on the device, so no other form of connectivity is needed.