Audio Barcode

NTT DOCOMO has been researching and developing "Audio Barcode," a technology that allows data, such as text information describing website URLs, to be carried and transmitted on sound waves in the audible range (music and spoken word).

Use of 2D barcodes - two-dimensional figures that represent data such as URLs - is widespread in Japan. The 2D barcodes appear frequently in advertisements and magazines, and allow users to access related websites by scanning these figures with mobile phone cameras. Audio barcode represents and transmits data in a similar way. Data embedded in sound waves are picked up by target devices with a microphone (mobile phones, for example), analyzed by special software, and then extracted.

Data to be transmitted is superimposed (embedded) by Acoustic OFDM, the technology behind Audio Barcode, in such a way that it is not detected by listeners. With a transmission rate greater than 1kbps, a URL or simple text transmission takes a mere one to two seconds.

Data to be transmitted is converted to sound waves using a modulation technique known as Orthogonal Frequency Division Multiplexing - the "OFDM" in Acoustic OFDM. OFDM is used by terrestrial digital television and wireless LANs such as IEEE 802.11a/g. Sound waves are then embedded and transmitted by means of a "carrier" - an original sound source. This data modulation technique enables highly-efficient use of frequencies, and expectations are that data transmission rates will continue to improve. OFDM is resistant to signal reflection and can transmit data with little or no error - even in an indoor environment where sound waves are subject to frequent reflection.

Merely adding sound waves to normal speech or music results in increased noise and will likely cause listener discomfort. The process behind Audio Barcode, however, removes a portion of the original audio source from the high-frequency range, which is difficult for the human ear to detect, replacing it with modulated data audio signals. Enhanced data cloaking is achieved through a new scheme we have developed that processes the audio signals to match the characteristics of the original audio source it will be replacing. Together, these technologies ensure that Audio Barcode is easy on the ears.

Information to be transmitted is relatively light, such as characters, and transmission time is very brief, several seconds at the most. Because the barcode uses the audible band of the sound spectrum, information can be extracted without need for special equipment. This benefit holds down the cost of deployment, and makes the technology suitable for widespread use.

If Audio Barcode is commercialized, we expect its use scenarios to include automatic transmission of website URLs to a mobile phone that is directed at a television set or radio. We also expect the barcode to add a new dimension to the mobile phone. For example, at an art museum, the mobile phone could be held before an audio guide in one language but display information in another language.

The day is at hand when the sounds of your everyday environment will be chock full of information.