Those articles mention uBeam's patent filings, but don't actually cite them. You can look at their patent applications.[1]

The overall system is described in their patent application #20120300593. This shows the overall plan: focus big transmitting transducers tightly on small receiving transducers. This resulted in a patent, #9094111. But to get the patent, they had to narrow the main claim to include "a receiver communications device adapted and configured to send input to the sender, the input comprising a power requirement that causes the sender to change a dwell time of the sender on the receiver". That's not an essential component of such a system, so it's not a broad patent.

There's an application on beam-steering, #20140281655. That's a known technology, and the USPTO has sent back a non-final rejection based on prior art. But that tells us the plan - big phased array of ultrasonic transducers aimed at a tiny target. Direct line of sight is necessary between transmitting array and pickup array.

How could they generate 155dB of ultrasonic energy? They applied for a patent on their transmit transducer, application #20140265727. That has an image of the sending transducer. It's a piezoelectric device with a silicon membrane, with a vacuum behind it. (The vacuum in back is to avoid pumping half the energy back into the device itself.) A "thin film" piezoelectric element makes the membrane vibrate. Devices like that have been built before, and the USPTO accordingly just sent them a final rejection. There's no new feature there which allows generation of more audio power than existing devices. So assume their device has performance roughly comparable to existing devices.

Here's a product list from American Piezo, a commercial supplier of high-power air ultrasonic transducers.[2] Their highest power unit that transmits into air is 119dB. uBeam is claiming 155dB. That's 36dB more, or 4000 times as much power. That device needs 30V into 2K ohms to power it, or about half a watt. So uBeam's transmitter would need about 2 kilowatts, comparable to a small clothes dryer, spread over a large number of transmitting transducers. An array 64 square would do it. The American Piezo transducer is 16mm across, so the transmitting array needs to be about a square meter. That's a big transmitting array, with 4000 elements, each with its own drive electronics. All that energy, or as least as much as they can focus, gets aimed at a tiny target.

The parent article discusses the attenuation problem. This gets worse with frequency.[4] Measured values of attenuation in air at 1MHz at 20C are between 160-165dB/m. This is huge. 1m from the transmitter, all the power is gone, used to heat the air. uBeam wants to operate in the megahertz range, but no way will that work. At 50KhZ, where most air ultrasonic systems work, attenuation is only 2dB/m. Their demo system (with about 1 foot range) used off the shelf 40KHz transducers.

This thing might work in the 50-100KHz range, with a rather large and expensive transmitter array, when the target device was facing the transmitter. Safety remains an issue; if they actually built a 155dB system, they'd have a steerable ultrasonic welder.

They could potentially build a nice demo system. Build a meter square array of off the shelf transducers running in the 50-100KHz range and mount it in a large picture frame. Cover it with speaker grille cloth, maybe with a picture silk-screened on so it looks like a framed picture. Have it scan at low power until a cooperating device reports a signal. Then focus the beam and turn the power up to full.

It's not going to be totally silent, because some harmonics will get through and some objects in the target area will vibrate with the ultrasonics and resonate at a lower frequency. But it probably wouldn't be noticeable at a noisy trade show.

You probably don't want to be near the focus of this thing.

[1] http://www.faqs.org/patents/assignee/ubeam-inc/
[2] https://www.americanpiezo.com/standard-products/air-transduc...
[3] https://en.wikipedia.org/wiki/Ultrasonic_welding
[4] http://www.ndt.net/article/ultragarsas/63-2008-no.1_03-jakev...