Playing catchup?
Alipay has been doing this for years.
Google's launched a payments service called “Tez” for India and plans to take it to other nations soon. Tez, the Hindi work for “fast”, requires users to possess either an iOS or Android device equipped with a microphone and speakers, download an app and then link their device to their bank accounts and the Unified Payments …
Sound is only the medium, just another kind of wavelength. It's not more or less easy to tamper than NFC, that will only depend on what transits on the wave, ie, how it's encrypted and what kind of user confirmation is needed.
The obvious advantage is that there are many more phones equipped with a microphone and speaker (duh...) than with NFC.
Sound seems a very brittle solution
As a very short range link, I don't see any problems not already present in other contactless systems. But I do wonder about the comment that this is ultrasonic - are the speakers and mics (and signal processors) all capable of doing ultrasonic communication properly?
I think "audio QR" is an incorrect or novel term. https://en.wikipedia.org/wiki/QR_code doesn't mention a version in sound, and Google of "audio QR" initially produces web pages about "how tu put an audio file on the Internet and then make a QR code that finds that file and plays it".
As I understand it, QR is specifically a format for a two-dimensional image which contains an encoded data file. You scan the image, decode it, and you have the file. Very commonly, the file contains a URL which is the address of further data. My weekly bus ticket now is a QR code on paper; it may or may not be a signed data file which represents a valid ticket for the current week - also presumably there's some tracking to prevent me selling photocopies of it to friends: if more than one person seeming to be using the same ticket then you get stopped. Having said that, I probably shouldn't flash it around at other times in case someone photographs it. Of course a criminal could just steal my actual ticket...
"audio QR" evidently is an ultrasonic data standard which similarly transmits a file, and it may not even have a proper name in English (one that isn't embarrassing). It needs electronic audio equipment to send and receive it but it doesn't need a visual display or printer or camera, so maybe that works better in India. It's probably pretty fast, and, being ultrasonic, it won't easily be recorded by a third party or send over actual phone lines, which filter down to spoken-word frequencies. And tapping it may do you no good anyway if it's like my bus ticket but only actually valid during the split-second that it's transmitted.
My basic impression of India from many many miles away, but watching it on television, is that it's d--- noisy - from (not) watching films like "Gandhi" and even before you consider the background music as well. On the other hand, slightly more reflection tells me, accurately or not, that lots of India is miles and miles from anywhere. No doubt the developers of the "Tez" dispenser have both of these situations in mind.