China’s leading online payments system Alipay is running a trial of vending machines in the Beijing subway that enable users to make mobile payments via the white noise generated by smartphones, according to Xinhua News.

Initially available at two sites, the technology will be spread across all the vending machines on the city’s Metro Line 4 next week. Users make payments via an Alipay wallet app on their smartphones and then connect with a sonic module embedded in the vending machines.

The audio payment codes generated by the user’s smartphone do not contain sensitive data such as their account information but only relate to a specific payment transaction, said the report. The codes are only effective for five minutes.

The cost of such vending machines is 15 per cent higher than normal ones, said vendor Qingdao Easy Touch, but offers greater convenience in areas such as counterfeit coins, giving change and bank exchange.