Linked by Thom Holwerda on Tue 10th Jul 2012 01:24 UTC
Microsoft "Microsoft and Perceptive Pixel Inc. (PPI) today announced that they have entered into a definitive agreement under which Microsoft will acquire PPI, a recognized leader in research, development and production of large-scale, multi-touch display solutions." Yes, Jeff Han is now a Microsoft employee. This demo still amazes me - from 2006. Before the iPhone. Before Android. Before the iPad. Remember that the next time you wind up in a discussion about who supposedly invented what.
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RE[4]: I built one too!
by Laurence on Wed 11th Jul 2012 09:57 UTC in reply to "RE[3]: I built one too!"
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Outside noise is not necessarily that much of an issue. If you stick the piezos inside of the device's casing, they will be far, far more sensitive to finger tapping and friction on the device's casing than to outside noise, since there's a lot of acoustic reflection going on at the air-casing interface. That, and acoustic power decreases as the square of the distance that is travelled from the source. To see how big the difference is, just gently tap the surface of a microphone when recording sound : you should get a peak that is far more intense than anything you were recording, even for a very gentle tap.

Pockets are indeed an issue, but on this front microphones are just as bad as capacitive touchscreens, which will also run amok if you forget to turn off your phone before putting it in your pocket. One specific pitfall of acoustic sensing is friction on the back or the sides of the device during device use though. Accounting for these could indeed require complex noise cancellation systems.

I understand the acoustics of it all (I've spent a lot of time working with mics as well). While I appreciate that outside noises isn't a huge issue most of the time, it will be an issue some of the time. For example, in night clubs where the sound system is well tuned for punchy kick drums. Such a touch pad under those conditions could be worse than useless.

You also then have to account for the amplitude of the sound (depending upon how heavy handed the user is), the different refractive properties of the casing for each unique phone handset and the subtle differences in the tune of the touch depending upon the make up of the casing (crude example: tapping a metal table produces a different sound to tapping a plastic table).

So I just think the amount of code that would have to go into understanding the difference between sounds originating from physical contact and those from external sources could amount to a more complex solution than having sensors detect physical contact via the resistance of the users finger. Though I will grant you that some of the above can be configured at run time by a control panel-type app - but even then, that means you don't have an "out of the box" solution unlike with the current method.

Further more, attaching a new phone case (eg rubber sleeve or patterned cover) would then also change the acoustics and thus potentially break the touch pad. Which would be a terrible step backwards in terms of usability.

Don't get me wrong, I think the mic'ed method is a fascinating idea and it sounds like great fun for a lab / home environment. I just think it's not better (or even practical) than current capacitive inputs.

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