[..] Every call into or out of US prisons is recorded. It can be important to know what’s being said, because some inmates use phones to conduct illegal business on the outside. But the recordings generate huge quantities of audio that are prohibitively expensive to monitor with human ears. To help, one jail in the Midwest recently used a machine-learning system developed by London firm Intelligent Voice to listen in on the thousands of hours of recordings generated every month. “No one at the prison spotted the code word until software started churning through calls“ The software saw the phrase “three-way” cropping up again and again in the calls – it was one of the most common non-trivial words or phrases used. At first, prison officials were surprised by the overwhelming popularity of what they thought was a sexual reference. Then they worked out it was code. Prisoners are allowed to call only a few previously agreed numbers. So if an inmate wanted to speak to someone on a number not on the list, they would call their friends or parents and ask for a “three-way” with the person they really wanted to talk to – code for dialling a third party into the call. No one running the phone surveillance at the prison spotted the code until the software started churning through the recordings. This story illustrates the speed and scale of analysis that machine-learning algorithms are bringing to the world. Intelligent Voice originally developed the software for use by UK banks, which must record their calls to comply with industry regulations. As with prisons, this generates a vast amount of audio data that is hard to search through. [..] <https://www.newscientist.com/article/mg23030762-200-prisoners-code-word-caug...>