Jan 10, 2008 at 2:47pm
Jan 10, 2008 at 8:15pm
Quote: bungalowbill wrote on Thu, 10 January 2008 06:47
Jan 10, 2008 at 10:17pm
Jan 16, 2008 at 12:53pm
thanks for your ideas,
i thought about using contact-microphones (attached directly to the floor) and use the step “noises” (excuse my english).
Jan 16, 2008 at 8:14pm
Contact mics seem like a good idea. You’ll still have to work out onset detection, but it might work.
Let’s assume for a moment, you’ve got perfect onset detection, the next thing you need is the time difference between the same event in different mics. Let’s imagine just two mics for now. Let’s put them 10 meters apart. The time difference will range from zero ms (when something is exactly between the mics) to about 29.4 ms (with sound moving at 340 m/s) when something is right on one mic. By the way, that’s the speed of sound in air; I don’t know the speed of sound through floor. You could calibrate your system experimentally, though.
Whatever the actual values, the time difference tells you how much closer the sound is to one mic. If the time difference is 50% of the maximum time difference, than the object is 50% of the way from the middle point to the mic where the sound arrived first. (In the example, 2.5 meters from one mic and 7.5 meters from the other mic, assuming the person stays on a line between them.) By adding a third mic, you could position a sound inside a triangle by comparing pairs of mics as above.
Am I making any sense? Accuracy will be important in this project. Below is a quick patch to compare the time difference between two clicks.
#P window setfont “Sans Serif” 9.;
Jan 16, 2008 at 9:25pm
The sound travels probably faster through the floor than through the
And what if there are several people walking???
Jan 18, 2008 at 4:21pm
hi mzed, hi stefan,
thanks for your ideas.
mzed: thanks for posting the patch, i copy & pasted it into a text editor & tried to open the file with max, but that doesn
Jan 18, 2008 at 4:32pm
sorry, it seems that i can
Jul 22, 2009 at 3:02pm
I’m working on the same type of position tracking.
I was wondering if you got your patch stable and working at all?
Jul 22, 2009 at 4:35pm
the basic concept seems a simple thing to me, you just measure the
the practice, well.
stepdance shoes might help.
Jul 24, 2009 at 10:27pm
you can easily make good onset detection doing the following (sorry don’t have max here):
- mic put your mic signal in an average~ 44100
now you have the rise and fall time of the sound, it indeed travels much faster through a floor than through air (+- 1000m/s vs 343 m/s) but is also much louder through the floor to te contac mic, so I think it should work.
you could use > some threshold in dB/s with a select 1 to generate trigger events
if you get retriggers, just change the “441″ to some higher number and/or make the threshold higher
Jul 25, 2009 at 10:49am
Here you go
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