&gt; This is what I don&#x27;t get - how the hell did they manage to get investors?<p>Because they did a couple of things <i>absolutely right</i> which was to pick something that&#x27;d have huge, giant, insane rewards if it works and picked something that&#x27;s not so crazy implausible that it would require totally new physics to work.<p>Sadly even if it does work I wouldn&#x27;t want it because even though you can&#x27;t hear ultrasound I&#x27;m sure it wears on your ears just the same.  The wavelength of 40kHz is 0.339 inches and 60kHz is 0.226 inches which are definitely on the right order of magnitude to resonate inside your ear which seems...sub optimal.  I seem to remember that their tech operates in this band.