How Chirp works

There are lots of different ways to embed and extract meaning from a piece of sound. Chirp uses audio data encoding — or modulation/demodulation. Data is encoded into a series of pitches and tones on the sending device, and decoded on the receiving device.

Why audio data encoding?

Audio data encoding — or modulation/demodulation — is a technology that has been used since the early days of radio communication. Strengths: It does not require an existing audio signal to operate on. Instead, data is encoded by generating a new signal whose properties are determined by the data to be transmitted. Information can be encoded and decoded in real-time, without any external components such as a look-up database. It’s a good fit for compact, dynamic payloads, which means it’s appropriate for creating network-like communication links between devices. It has a relatively high throughput making it suitable for security-critical applications such as exchanging authentication or payment tokens.

Audible or Inaudible Ultrasound?

Chirp technology is available in both audible and inaudible (ultrasound) across our full product suite. Here are some advantages, limitations, and potential use cases of each


There are several advantages to using audible sound to transfer data. These include: - It’s more widely supported than ultrasound. Audible methods of data transfer work across a wider range of devices and media than ultrasound (e.g. AM/FM/DAB radio, many online video streaming sites, telephones, etc). - It’s able to carry more data. Audible can transmit the greatest amount of data reliably because it uses a wider frequency spectrum than ultrasound. - It works well in a wide variety of environments. Audible is robust and reliable in the most challenging acoustic environments. - It is audible. Audible is honest and transparent. The data transfer is heard. Some typical use cases for audible technology are: - Embedding into AM/FM/DAB radio broadcast and some online video platforms which strip out ultrasonic frequencies. - Broadcasting over loudspeakers or PA systems to a fleet of machines or devices. - Communicating with old, basic or lo-fi audio equipment. - Scenarios where larger amounts of data must be sent to devices which are offline, such as transmitting video game characters and trading cards.

Inaudible (ultrasound)

Advantages to using ultrasound to transfer data include: - It’s inaudible. Ultrasound can be used to silently transfer data from one device to another. This is powerful in situations where users are concerned about noise pollution or where other audio or music is playing. - It can be used as a ‘beacon’. Unlike audible Chirps which are typically played once, ultrasound Chirps can be played continuously on a loop. This means they can broadcast information to passers-by, effectively acting as an audio ‘beacon’. - It can be embedded into other media. Because ultrasound uses a different frequency band, it can be played alongside other audio (even from the same loudspeaker) without interference or loss of reliability (this assumes that ultrasonic frequencies are supported by the audio equipment or media player). This means ultrasonic Chirps can be embedded into music, TV programmes, sonic branding, jingles or audio alerts. Some typical use cases for audible technology are: - Synchronising second-screen applications with TV broadcast in real-time. - Embedding vouchers and offers into TV ads, which can be received by an app. - Proximity marketing in retail locations to deliver product information and offers to shoppers. - Making brand jingles come alive and become interactive. Chirp’s audible and ultrasound technology is available on iOS, Android, JavaScript, Python, Windows UWP, Linux, Arduino, Raspberry Pi, Smart TV platforms and web browsers.

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