I suspect the new volume control method could have something to do with the following paragraphs from the recent patent:
"... 7. Apparatus according to embodiment 2 where the first electrostatic force described in embodiment 1 is adjusted in such a way as to limit the range of movement of the moving elements along their respective to a range shorter than that defined by the mechanical limiter. ..."
"... Other control algorithms may also take account of the actuator elements' impulse response in order to more accurately reproduce the digital input signal. Control algorithms may also include additional signal processing functions such as but not limited to volume and tone control as described in Applicants' co-pending application WO2007/135679, entitled “Volume And Tone Control In Direct Digital Speakers”. In general, the number of values that the digital input signal assumes may differ from the number of actuator elements in the apparatus, and therefore the controller may include a scaling function to match the digital input signal to the number of actuator elements available. ..."
Being able to limit the movement to a shorter "stroke" could allow some additional volume control, whether that is used to synchronise all the pixels together or to control their overall sound volume, or to limit the volume without affecting the frequency of the sound.
Whatever it is, the sheer ingenuity of the way the device functions indicates the extent of the work that has gone into the development. But also the extent of the improvements is reflected in the changes of the patents over the past couple of years during which the team has been encountering and solving so many of the problems to date. The patent speaks volumes if you understand what it represents (and if you'll excuse the pun!). For both reasons I take my hat off to the team that have done this work, and remain convinced that the company really does know that they really do have an absolutely revolutionary product to take to market.
(20min delay)