Researchers have developed a new method for transmitting data to smartphones – by embedding it in music. That means phones might one day receive Wi-Fi passwords or local information via tunes floating through the airwaves, with no perceptible change to the audio as far as the human ear can tell.

The innovation is potentially going to be most useful in public spaces: hotels, shops, museums, transport hubs and parks, for example, where the background music could broadcast information about the venue or the business (and about how to log on to the local Wi-Fi network) as well as adding to the ambience.

You might get details of an exhibit beamed to your phone in an art gallery, or news of special offers in a department store, or the times of the next trains, without you having to touch your phone.

The researchers behind the technique, from ETH Zurich in Switzerland, say the changes the data transmission makes to the music are imperceptible. The more data that needs shifting though, the more heavily the audio file needs to be modified – speeds of around 200 bits or 25 characters per second are possible without a noticeable change.

"In theory, it would be possible to transmit data much faster," says one of the researchers, Simon Tanner. "But the higher the transfer rate, the sooner the data becomes perceptible as interfering sound, or data quality suffers."

It's not enough bandwidth to transmit the works of Shakespeare, but definitely enough to send over a Wi-Fi access code to save you having to type one in when you arrive at a new hotel or conference venue.

The actual modifications are applied to the dominant notes in a piece of music – overlaying each note with two marginally higher and two marginally lower notes, with a similar process applied to the harmonics of the strongest note.

"When we hear a loud note, we don't notice quieter notes with a slightly higher or lower frequency," says another of the ETH Zurich researchers, Manuel Eichelberger. "That means we can use the dominant, loud notes in a piece of music to hide the acoustic data transfer."

Music with a lot of dominant notes works best for the technique – so think the latest pop hits rather than subtle background music.

A map to the modified notes is put in the 9.8–10 kHz frequency range, a part of the frequency spectrum that is barely picked up by the human ear. The final step of the process is the microphone on a smartphone, which could be primed via an app to capture the data being sent.

In an industry gearing up for the arrival of 5G, it's interesting to see something much slower but a lot more convenient get proposed and demonstrated. Embedding data in music could be another way of keeping our phones connected in the years ahead.

Source: ETH Zurich