An app that transmits data via a burst of "digital birdsong" aims to simplify the way users share images and other files between smartphones. Chirp plays a two-second long noise that sounds as if it was made by a robotic bird. When heard by other devices it triggers a download. The software was developed by Animal Systems, a spin-off business from University College London (UCL). It is free to use, but companies will be charged a fee for add-on services. At the moment users are limited to sending pictures, website links or 140-character text messages. These appear in a feed similar to Facebook's timeline. Other applications such as Android Beam, Bump, Datasync and Dropbox allow users to swap material via bluetooth, wi-fi or links to cloud-based storage. But Chirp has the advantage that it can quickly send data to multiple devices at once without them needing to be either paired or have a wireless connection. If recipients are offline their devices will remember the "chirp" and download associated content later. "We are pretty sure this is unique," the firm's chief executive Patrick Bergel told the BBC. "We solve the problem of having to pair devices to move data. It's fairly novel to be able to transmit information to anyone who is in earshot - a large number of devices can share the same information at the same time using sound. "You can also use it as a device shifting mechanism. In the future you will be able chirp yourself a link to a map from your laptop." Mr Bergel says Chirp's distinctive sound allows it to work at low volumes in relatively noisy locations such as pubs, clubs or busy streets. It can also work over public address systems or radio transmissions - potentially allowing broadcasters a way to send up-to-date pictures or links to background information; or an advertiser to send coupons or snippets of a song or promotional video. Animal Systems subscribes to a "blacklist" service to prevent users transmitting known pornographic or illegal-content website links. However, it does not plan to moderate other material. The application works by uploading a user's material to the firm's servers. The data is then identified with a 50-bit address space: one of trillions of available identifiers. This location is then sent to the sender's device. When the user presses a button in the app it plays an audio-encoded version of the address. Copy-protected Data has long been passed between machines in the form of sound, including recordings on tapes used to load programs into 1980s home computers and early modems dialling into networks. Even so, Mr Bergel said he had taken steps to prevent others copying his product. "We have a systems patent on moving short codes over the air," he said. "We have [also] solved a lot of difficult problems. There's a lot of technical issues around moving data and making it robust against noise and echoes." Having launched the app the five-man team behind it will now focus on offering premium services to marketers and other businesses. Mr Bergel said these could include: A guarantee that uploaded content would be permanently kept on the firm's servers. Access to analytical data letting firms track whose devices have "listened" to their chirp. The ability to send video messages that play within the Chirp app. Mr Bergel said the ultimate goals was to see manufacturers pre-install Chirp on handsets. However, he must first convince users that they need the service at a time when wi-fi, 4G data and advanced bluetooth connectivity are becoming increasingly common. For now Chirp is only available as an iPhone app. An Android version is promised "soon".