3 ms·

I can't work out if that would be possible or not. It might be possible to plot the location of a single point in 2D, but how would you differentiate for multi

by edlea 15y ago

I can't work out if that would be possible or not. It might be possible to plot the location of a single point in 2D, but how would you differentiate for multitouch? If you have 2 microphones you might be able to calculate the distance from each microphone of a touch by timing how long it takes for the sound of the tap to reach each microphone. However, as the speed of sound in wood appears to be ~4000 m/s (http://www.engineeringtoolbox.com/sound-speed-solids-d_713.html http://www.engineeringtoolbox.com/sound-speed-solids-d_713.h...) you'd need to be "listening" at 400kHz to get centimetre accuracy over a 1m square area. I can't see how it would be possible to then differentiate between two points moving at the same time (i.e. a pinch gesture). I'm just assuming regular microphones are used as the article suggests - I'm not an acoustic engineer so hopefully I've missed something.

kabdib 15y ago
Use a phased array of mics. Classic technology (well, 1960s). Probably much harder with random mic placement.
- nitrogen 15y ago
  Probably much harder with random mic placement. You could run an initial calibration on the system by having the user tap a large number of points within the touch area and noting the relative phase, amplitude, and frequency content received by each mic for each location.
ww520 15y ago
Interesting problem. Haven't thought of the sampling rate required. The location resolution probably will be poor for precise multitouch function. But even a single 2D location is enormously useful - turning any surface into a touch screen. kabdib mentioned phrased array, which can be very helpful. It might solve the sampling rate issue since it's analog. I found this http://en.wikipedia.org/wiki/Beamforming http://en.wikipedia.org/wiki/Beamforming. May be some of the techniques in radar/sonar can be borrowed here.

by edlea 15y ago

kabdib 15y ago

Use a phased array of mics. Classic technology (well, 1960s). Probably much harder with random mic placement.

nitrogen 15y ago
Probably much harder with random mic placement. You could run an initial calibration on the system by having the user tap a large number of points within the touch area and noting the relative phase, amplitude, and frequency content received by each mic for each location.

ww520 15y ago

Interesting problem. Haven't thought of the sampling rate required. The location resolution probably will be poor for precise multitouch function. But even a single 2D location is enormously useful - turning any surface into a touch screen. kabdib mentioned phrased array, which can be very helpful. It might solve the sampling rate issue since it's analog. I found this http://en.wikipedia.org/wiki/Beamforming http://en.wikipedia.org/wiki/Beamforming. May be some of the techniques in radar/sonar can be borrowed here.