Friday format: How digital money “sounds”

This fall, Google introduced a new payment application for India. Its feature was the technology that allows you to transfer funds by transferring data between mobile devices using sound.

Since 2013, in the Beijing metro, there are automatic machines that take money for the fare on the same principle. All that is required of passengers to pay for the trip is to launch the application on their mobile phone and bring the smartphone closer to the sensor on the machine.

The basis of these decisions is the principle of data exchange over the audio channel. Mobile payments are just one of the possible applications. In this article we describe the advantages and disadvantages of technology, as well as recall successful solutions.

Photo hobvias sudoneighm CC BY

How it works

Using sound to transfer data is not a new technology. In the 40s of the 20th century, IBM developed a method for converting data into sound for the exchange of messages between two computers. Not long ago, modems used modulation to exchange data over a telephone line. A new stage in the development of audio data has come with the widespread use of mobile phones.

To transfer information about the transaction data is converted to an analog signal. For this, modulation is used , and on the receiving side there is a device for decoding the message. There are several implementation options for this transmission technology: amplitude, phase, and frequency modulation.

The new technology is wireless and contactless, which puts it on par with Bluetooth, Wi-Fi and Near Field Communications (NFC) when it comes to mobile transfers. Based on the latter solution, popular payment systems such as Apple Pay and Android Pay are based. NFC provides wireless communication and data exchange between digital devices through embedded chips.

For the "sound" data transfer you need a source and receiver - the speaker and microphone of the phone. The transfer does not depend on any particular platform, and the security of the connection is ensured by means of tokenization, multi-level encryption, and multi-factor authentication.

There are applications that allow transfers only between users' devices, and there are solutions that offer work with payment terminals.

One of the technologies that allows for transactions over an audio channel is called Near Sound Data Transfer . In this case, the security of transactions provides an electronic signature, which is formed on the basis of a one-time password transmitted via the audio channel of the mobile device.

There are applications that "connect" mobile devices with a TV and laptop. They allow you to receive information about a product that is advertised on the screen by analyzing an additional component of the ether - ultrasonic beacons , the use of which is often referred to as “spying” on the actions of smartphone users.


In late November, it became known that contactless payments in Russia have tripled. Users began to appear more and more smartphones with NFC-chips, and retailers - terminals for making payments. But this situation is not in all countries.

In India, where Google came with its payment application, there are 300 million smartphone users, but phones with NFC chips are still relatively rare because of their cost. Not the best case with the availability of the Internet.

Locals choose simpler devices because they still do not have the ability to connect to a high-speed connection. The number of credit card holders in India reached a record high this year. This means that the country is ready to introduce mobile payments, but there is no infrastructure for this.

New data transfer technology, including for mobile transfers, is a good alternative to other payment methods due to the availability of this solution. It is compatible with all mobile phones with different operating systems and can be adapted for EDC and POS devices.

This technology is more convenient and safer than QR codes that have already gained popularity amid the problems of the Indian financial system.


The developers of one of the solutions, called AudioModem, note that the main limitation of the technology is the “sensitivity” of amplitude modulation to background noise. Therefore, in their version they used the phase manipulation method (Differential Binary Phase Shift Keying - DBPSK), and the final solution was published on GitHub.

Representatives of the startup Tchirp also note the limitations of the hardware, including device performance and microphone quality. Today's smartphones do not have enough computing power to simultaneously record and decode information encrypted in "ultrasonic" messages.

Although it is claimed that the technology provides a high level of security, the threat of hacking remains . Infection of one device may cause the data of all counterparties involved in transactions to be compromised.

What else can be transmitted using this technology

Mobile payments are a great use-case. Not only in developing countries, but also in the USA and Canada such services as Naratte, Paytm, Ultracash, ToneTag, Soundpays, MoboMoney operate. But there are other areas of application.

In Google, data transmission over the audio channel became interested long before the development of the Tez application. In February 2014, the corporation acquired the startup SlickLogin, which used ultrasonic signals for two-factor user authentication. A year after the completion of the transaction, the Google Tone extension was launched, which provided another way to exchange links with office colleagues.

There are other examples. Quietnet allows you to create encrypted chat rooms and communicate using ultrasonic transmission. Chirp - share photos, videos, links and notes. Lisnr works in a similar way.

Like NFC and QR codes, audio transmission is used in marketing campaigns to turn offline customers into online users. For example, Signal360 is engaged in technology that provides reproduction of high-frequency sound waves through speakers or small beacons in stores that send messages (coupons and invitations) to users' smartphones.

An even larger scope of technology is the Internet of Things. IoT devices can exchange information using only the speaker and microphone. For example, you can set up or update thousands of devices through an audio channel using a speaker or computer, says Daniel Jones, chief researcher at Chirp, which also makes such decisions.

Sound-based data transmission has many potential applications, but there are also shortcomings that prevent technology from expanding and dominating each of these areas. The solution can be viewed as an auxiliary, for example, as a startup Zoosh does. It promotes mobile transactions over the audio channel, but does not seek to replace NFC — according to its founders, this data transfer technology will be useful to consumers until NFC chips appear in all smartphones.

What else do we write in our “ Hi-Fi World ”:


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