One of the biggest pain points to digital voice assistants is that using them in public is incredibly awkward, and most people don't do it. Despite numerous advertisements showing people like Martin Scorsese using voice assistants in public, it really doesn't happen much.
In a rather interesting patent by Microsoft (as opposed to yet another patent for a foldable dual-screen device), the firm patented (spotted by Windows Central's Jez Corden) a way of handling silent voice commands.
It does this by listening differently. Instead of just listening for egressive airflow, it listens for ingresive airflow as well. Here's how it's described in the patent:
Implementations of the subject matter described herein provide a silent voice input solution without being noticed by surroundings. Compared with conventional voice input solutions which are based on normal speech or whispering that use egressive (breathing-out) airflow while speaking， the proposed “silent” voice input method is performed by using opposite (ingressive or breathing-in) airflow while speaking. By placing the apparatus (e.g. microphone) of the apparatus very close to the user’s mouth with an small gap formed between the mouth and the apparatus， the proposed silent voice input solution can capture stable utterance signal with a very small voice leakage， and thereby allowing the user to use ultra-low volume speech input in public and mobile situations， without disturbing surrounding people. Besides of air flow direction (ingressive and egressive) ， all other utterance manners are same as our whispering， so that proposed method can be used without special practice.
The images shown on the patent show various methods of implementing the new idea. It shows it as being integrated into various devices such as smartwatches and smartphones, which the user would hold up to their mouth to use. There's also a standalone device, which could connect to your phone. This is particularly interesting, because a standalone device might be able to be used for voice assistants that aren't made by Microsoft.
As with all patents, it's just an idea. Time will tell if this technology ever sees the light of day.