https://www.theverge.com/2018/3/16/17128860/amazon-alexa-brief-mode-testing-responses-verbal-beeps

Tech companies are still working out how users want to interact with voice assistants, but it seems one option is making them less chatty. Amazon, for example, is apparently testing a new “brief mode” for Alexa devices that replaces some of the virtual assistant’s verbal responses and confirmations with beeps.

Users on Reddit were the first to report the feature with AFTVnews picking it up. One Redditor writes: “I just asked Alexa to turn on my lights, she said ‘OK’ just like normal, but after that, she said that this would be the last time she would, and that I would hear a beep tone instead on a successful command.”