Amazon details the AI behind Alexa's Whisper Mode

In October 2018, months after a brief reveal, Amazon brought Whisper Mode to select third- and first-party Alexa devices. It expanded the feature to all locales in November 2019, such that all smart home appliances powered by Alexa -- the company's virtual assistant -- now respond to whispered speech by whispering back. Amazon was a bit light on the technical details initially, save that Whisper Mode uses a neural network -- layers of mathematical functions loosely modeled after the human brain's neurons -- to distinguish among normal and whispered words. But in an academic paper appearing in the January 2020 issue of the journal IEEE Signal Processing Letters and an accompanying blog post, it detailed the research that led to the expansion. The principal challenge was converting normal speech into whispered speech while maintaining naturalness and speaker identity, explained Marius Cotescu, an applied scientist in Amazon's text-to-speech research group.