Phase shift analysis - Page 1
Forum section: electronics / general

author: Mcfly
author_rank: Contributor
timestamp: December 27, 2012, 03:49:55 am
content: Does anyone know how to measure the phase shift of multiple audio signals on microphones?My goal is to design a sound ranging system to find the direction of sound sources (ie german artillery pieces)http://en.wikipedia.org/wiki/Sound_rangingIt would be nice if all i need are passives, lm324 op amps, and a couple channels of 10 bit adcThe amplitude and 'profile' of the sound signal would be somewhat variable..Would a peak detector -- interrupt combo be good? I could to the rest of the crap on the arduino maybe...Thanks -- Garrett

author: SeanB
author_rank: Super Contributor
timestamp: December 27, 2012, 04:39:44 am
content: You need at least 4 microphones and a known distance between them, so you can measure time of arrival at each mic ( loud enough noise so easy to discriminate) and use simple trig to calculate the arrival angle.

author: Wytnucls
author_rank: Super Contributor
timestamp: December 27, 2012, 05:33:51 am
content: German artillery officer: Haaa...but vee haf vays to defeet you! Vee shell send our 'Oom pah pah' bands to the Western front soon! Dumme Leute...

author: Mcfly
author_rank: Contributor
timestamp: December 27, 2012, 05:45:10 am
content: But how will I find delta t?Its probably a stupid question...

author: Kremmen
author_rank: Super Contributor
timestamp: December 27, 2012, 08:38:12 am
content: Err... by using a timer?For single impulse sounds the simple time difference measurement may work. But if there is any distance - i suspect you won't be allowed in the immediate vicinity of the artillery pieces - the signal is confused by multiple pathway sound travel, echoes and spurious noises.The "proper" way to do it would be to arrange the transducers (mics) in a 2 dimensional matrix (i assume you don't need the vertical component). Then measure the sound waveform from each mic and run a signal correlator algorithm between all of the incoming waveforms to find out the arrival time differences of each signal to the individual mics. After this you need to solve the multiple equation for each set of time differences to find out the directions of each individual source.The calculations are somewhat involved and you really need a proper DSP capable device to pull it off.

author: ftransform
author_rank: Frequent Contributor
timestamp: December 27, 2012, 08:38:55 am
content: Quote from: Wytnucls on December 27, 2012, 05:33:51 amlmfao

author: codeboy2k
author_rank: Super Contributor
timestamp: January 02, 2013, 05:23:31 am
content: Quote from: Kremmen on December 27, 2012, 08:38:12 amThese arrays are pretty cool, they can be "steered" mathematically to focus on an individual in a crowded room where everyone is talking at once. I can see them easily being used in a future large scale installation at crowded venues like airports and Olympic games, for example. They will be mated with vision systems that can track an individual in a large crowd and hear what that person is saying. Multiple arrays in these venues will give full coverage and better tracking. It will come.

author: FJV
author_rank: Regular Contributor
timestamp: January 02, 2013, 05:45:02 pm
content: Quote from: Mcfly on December 27, 2012, 05:45:10 amIt is propably a stupid answer, but.Seems like you want something similar you find in a synchro resolver.http://www.google.com/url?sa=t&rct=j&q=synchro%20resolver%20schematic&source=web&cd=3&ved=0CEsQFjAC&url=http%3A%2F%2Fwww.ddc-web.com%2Fdocuments%2Fsynhdbk.pdf&ei=FnHkUMidO-iU0QXUh4G4AQ&usg=AFQjCNF5tlhODfRKPbbBEiVRh-0uO8HmCg&bvm=bv.1355534169,d.d2k&cad=rjaYou could try to rework the math in this link so that you can calculate delta T by using the original amplitudes and the amplitude of the sum of the signals.http://www.electronicstheory.com/html/e101-25.htm