| Author | Message | ||
     Ray Price Rating: N/A |
Ok, this is just a thought and may be completely unfeasible but I was trying to think the other night how to create a tracking device using regular objects that are low cost and that we already have. I was reading up on how GPS works by sending radio signals from satellites that are sync'd with atomic clocks and then calculating the distance from each satellite by working out how long the signal took to get from the satellite to the receiver. This is an over-simplified view I'm sure, but bear with me. So, my next thought was... why can't something like this be done for a local setup. Obviously radio waves would travel far too quickly so something slower would be needed, so my first thought was sound. What if a 5.1 system sent regular high frequency blips from each of it's speakers and you used a microphone as a tracker and had software to calculate the relative distance between each of the speakers based on the order and timing of the frequencies on the sampled signal? I am not a physics buff, so I don't know if the resolution of soundcards would be high enough to pick up the difference in such a small physical space. I believe the Audigy for example can sample at a rate of 96khz. Can anyone who knows more about physics than me comment? Thanks | ||
| Ray Price Rating: N/A |
I am not a physics or math expert, but I have tried some lamens calculations here. The Soundblaster Audigy can sample at a rate of 96khz. Sounds travels in air at approximately 345 meters per second. Therefore to travel one meter it takes 0.00289 seconds. If 96khz means 96000 samples per second, then that gives a sample every 0.0000104166 seconds. That means a potential 277 samples per meter which could give an accuracy of 0.00361 meters (or 0.3cm). Sounds good. Obviously this is assuming the software could process the signal in realtime. I am assuming some type of Fourier Transform would be needed to split the frequencies back out. I am not sure how quickly that can be done. | ||
| Alatar Rating: N/A |
AFAIK any frequency-based approach would have a very high overhead in terms of lost resolution -- your 3mm resolution might deteriorate an order of magnitude or more. How about a simple time delay calculation: send a very short tone on speaker 1, wait x msec, short tone on speaker 2, and so on. You would then have a longer delay at the end. As long as the speakers could start and stop oscillating fast enough (and with repeatable performance), the difference in the delays between tones would locate the microphone. There used to be a device called the RingMouse -- which used a microphone inside a ring you wore on your finger -- which used a similar approach. We tested one, it never worked too well. | ||
| Alatar Rating: N/A |
This was it: http://referate.mezdata.de/sj2003/virtual_reality-comi/ausarbeitung/ring.html | ||
| Anonymoose Rating: N/A |
Using acoustics for trcking/mapping has been done before. The main thing is to set up reference points. ie- stand in a corner of the virtual box and take a sample. When you're finished chugging through the numbers on your Cray, you'll have a great way to tell where in that box you are. This is simple sonar principles, people. Do a library search of old Popular Science mags or something to get the basics. |
