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iOS App Acoustically Measures Distances Up To 25 Meters 154

Posted by samzenpus
from the new-tool-for-the-box dept.
n01 writes "A recently published app for the iOS platform uses the propagation of sound waves to measure distances of up to 25 meters in a dual device mode. The technique works through repeatedly sending a chirp signal from the master device to which the other (reflector) device synchronizes itself and then replies in a similar fashion. A novel combination of techniques has been engineered to enhance the robustness in noisy environments, such as using an optimum-autocorrelation-signal and semi-automatic frequency calibration together with an averaging over multiple cycles."
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iOS App Acoustically Measures Distances Up To 25 Meters

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  • Nifty (Score:1, Insightful)

    by Anonymous Coward on Sunday November 13, 2011 @04:11PM (#38042822)
    But still an advertisement.
  • by Tyrannosaur (2485772) on Sunday November 13, 2011 @04:12PM (#38042838)
    I thought this was going to be a cool sonar thing- you'll need 2 iphones? get a tape measure...
  • by sugarmotor (621907) on Sunday November 13, 2011 @04:35PM (#38042992) Homepage

    This didn't seem to do that good of a job, but was 2 years ago.

      * Sonar Ruler, By Laan Labs: http://itunes.apple.com/app/sonar-ruler/id324621243?mt=8 [apple.com]
      * http://thenextweb.com/2009/08/20/amazing-iphone-app-lets-measure-distance-echoes-works/ [thenextweb.com]

    Happy measuring!

  • Re:Not impressive (Score:2, Insightful)

    by Anonymous Coward on Sunday November 13, 2011 @05:10PM (#38043176)

    Yes, but for example the iPod touch (for which this software is supposed to work) is not a GPS enabled device. But there is no need for clock synchronization anyway, the way they use their two devices. Since the second device replies after a certain delay, the first device just has to take into account that the time difference between signal and reply is twice the travel time plus the delay (and then correct for the offset introduce by microphone and speakers not being at the same place... :) ).

  • Stand-alone (Score:4, Insightful)

    by soundguy (415780) on Sunday November 13, 2011 @05:14PM (#38043186) Homepage
    About 20 years ago, I had a hand-held device roughly the size of a smart phone but twice as thick that did distance measuring all by itself. It was infrared and as I recall, it was something like $25.00 from Rat Shack or Home Depot or some place like that. A 30 foot tape measure is about $8.00 and works a lot better.
  • by DrgnDancer (137700) on Sunday November 13, 2011 @06:01PM (#38043392) Homepage

    One suspects that the primary use case for this application is not, "Hey, we need to measure this, let's go get two iPhones!" It's "Hey we need to measure this and happen to have two iPhones, but no tape measure." Most people carry their phones around with them all the time, but unless they're contractors don't carry tape measures. The point of near ubiquitous mobile computers is that you can use them for lots of things. This is a cute and clever thing that you can now use them for.

  • Re:Nifty (Score:5, Insightful)

    by bonch (38532) on Sunday November 13, 2011 @06:22PM (#38043512)

    So Slashdot can't report on anything, ever, if it's for sale somewhere. Got it.

  • Re:Frequency? (Score:4, Insightful)

    by Anonymous Coward on Sunday November 13, 2011 @11:13PM (#38044984)

    Is there any benefit to moving to ultrasonic frequencies? Other than making it inaudible (so you don't bother people but maybe dogs!), would this improve the resolution? Does the range decrease? Do consumer level devices cover such a broad spectrum?

    As I mentioned in another comment, I've been experimenting with a similar application on iOS devices. Yes, consumer devices do cover ultrasonic frequencies, but barely. For average humans, ultrasound begins above 18 - 19 KHz, and devices with 48KHz range can produce up to 24KHz frequencies... in theory. The problem is that the commodity speakers/microphones in smart-phones are optimized for the human perceptual range, and since ultrasound is beyond that, the transducer dynamic range and/or the in-built signal processing conspire to significantly attenuate and distort ultrasonic signals. Using an iPad, in preliminary experiments, I could only get a range of ~5m using ultrasound, whereas these guys say they can go up to 25m.

    Moving to ultrasound also can affect resolution negatively. Since you're effectively using a much smaller bandwidth signal, your positioning accuracy reduces, on top of which, multipath problems get much worse. (Smaller bandwidth because by limiting the signal to ultrasound, you only get a bandwidth between ~18KHz and 24KHz for a 48KHz sampling frequency, and the iPad microphone strongly attenuates signals after the 20KHz range.)

    Also, how DO bats build up a good 3D map of their surroundings using just one "speaker" and two "microphones"? Do they send out beams or are their ears swiveling? And, with the limited amount of computing power on a smartphone, would it be able to duplicate it? A bat's brain doesn't seem particularly large and they are doing this FAST (on the fly, ha ha).

    Bat ears are highly specialized. This link gives a brief overview of how bats do echo-location:
    http://science.howstuffworks.com/environmental/life/zoology/mammals/bat2.htm

    I believe smartphones have, or will soon have, enough processing power to do the necessary signal processing if we can design the right algorithms. The problem is it would also need highly specialized audio transducers to get any useful signals, which may not necessarily fit into a smartphone form factor.

  • by BitZtream (692029) on Monday November 14, 2011 @12:08AM (#38045202)

    You could measure room wall lengths close enough for basic estimates on how much paint to buy or fence length estimates and such where you don't need cut to fit accuracy.

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