AKP (ASX) Whispers of a working chip

Originally posted by BobF ↑

Sorry, not correct. The pixels are not actually vibrating at 200KHz. If they were the array would simply be producing ultrasonic sound at 200KHz. They could do that, but that is not what is happening. 200KHz is its switching capability. Under the control of the software it is being pulsed forward then at later time pulsed backward whenever and only whenever it is required. Sometimes it is only moving once then doing nothing for a while. Each pixel pulse is contributing to the "mexican wave" that makes up the audible sound waveform as and when required. To make a lower frequency sound the pixels are being turned on and off in a 2D pattern across the face of the array (see the video for this). At some times within the audible sound's sine wave some pixels are being driven often while some less often. At the largest amplitude of the sound's sine wave many pixels are synchronously pushing air forwards (many claps), at the negative portion of the sine wave these same pixels are pulling backwards to pull the air backwards. During each sine wave the pixels are being actuated many times, but in a controlled manner. Together these many pulses make up the sound. For every low frequency sound produced, the pixels move many times to add more air movement to the sound. But it is the controlled change in the number of actuations over time that makes the resulting sound frequency, and the total number of pixels that produces the amplitude, i.e the volume of the sound. The more pixels that are moving over time the greater sound volume. The whole idea is that many small claps add together, or stack, one on top of another over the course of each sound wavelength. The result is sound of any (audible) frequency. The whole point is that by adding many small pulses together a very big sound - i.e. actual air movements - can be produced. To increase the SPL simply requires using more pixels in the array - i.e. more chips.

This is explained way more clearly and in far more tech detail in the tech videos. I've just tried to express it verbally in a quick way that I find gets the guts of it across. Sorry if it is still not clear enough though! When you see it - and hear it - happening you will click better.

AP generates the same SPL as other speakers, but using far less energy. In conventional speakers the majority of energy of the signal is converted ultimately to heat simply by having to accelerate and decelerate a relatively heavy membrane - not just the air. Only a fraction of the signal power turns into SPL. Not so here. Just think LED lamps vs incandescent lamps: same lumens but far lower wattage required to make the same amount of light.

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Reading through this I think I have explained it incorrectly. I do not think individual pixels are moving many times during each audible wavelength. As I understand it, over the course of the positive sine wave a growing number of groups of pixels are driven forwards (up) to the top of their stroke, then return to their centre position by the next clock tick. (This is the bit I am not quite sure about the more I follow the development of the tech!) The reverse happens when the sine wave turns to zero amplitude and then goes negative. The same groups of pixels then switch to backwards (down), i.e. to the other extreme position of their stroke. With every clock tick a new group of pixels is switched in. Over progressive ticks another larger group is switched in, with the largest group being added at the maximum sine wave amplitude, and with progressively smaller groups being added in as the wave falls towards zero amplitude. At zero the process reverses, with the same groups being switched to full backwards (down) in the same progressive order. It does appear that at zero amplitude all the pixels are either centred (or passing through) the centre position. This is graphically depicted on the video as a whole series of pixel actuation sine waves within the audible sine wave. The pulse direction is either up or down in each segment of the sine wave, or in the centre.