acoustic / WFS /
Digital loudspeakers in Holophony application
The development of „ Digital Loudspeakers“currently is topic in science. That doesn't mean the digitally guided analogue speakers, as associated by the phrase always, digitally loudspeakers actuate by the binary signal itself.
In that purpose the diaphragm subdivided in very small segments. These segments are connected in groups, according the weight of the steering bit. If the group switched by the binary signal, the air pressure in front of the digitally loudspeaker increase in the according steps. Until today 8 bit resolution is realised in the experimental set-ups. That is shown in the sketch for six different level steps:
Each subdivision is only switched, no requirements regarding linearity remain. In principle all, dynamic, piezo- or electrostatic solutions would be possible. But the single elements must change its level very fast. Only one cycle of the sampling frequency remain for its work. Thus only very small elements seem suitable. By Carnegy Mellone University realised the digital loudspeakers as integrated approach. Such tiny speakers currently intended for communication purpose only. Eight bit resolution cause more as -40 dB quantisation noise, that's inacceptable for HiFi - solutions.
Yet in the acoustic curtain of the described Holophony approach sufficient amount of single speakers supply the sound pressure on the listeners point. All work together, especially in the main range neighbouring speaker's posse's common movement of its diaphragm. Thus the perfect air resistance adaption causing high efficiency, very small excursions produce sufficient sound pressure down to the main range.
Over and above the quantisation noise hardly remains disturbing. Each elementary wave settles different distance to the listener. By that reason the levels of the quantisation steps are little different by this point. In summary we can estimate quantisation noise below - 96 dB for the proposed field from 1296 single speakers.
