I'm maybe completely off the chart and I'd really like to c the signal and do some measurements before I ramble about things like that .. especially as analog stuff are completely out of my area of interest ... anyhow .. rambling continues... if you look at the wave going from the speaker, you can assume some radial propagation of the wave ... that said, and that "visualised", the actual frequency of the sound should be slightly different with regards to the angle towards speaker...
looking straight at the sound you should count peaks at the frequency of the sent sound
Code:
-----+----------------------------------
O
O
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on the other hand, being under angle
Code:
----+-----------------------------------
O
O
-----------+----------------------------
now, after writing this, I'm doubting it but check this out .. the wavelength of the 600Hz is ~0.56m and for 1200Hz it is ~0.28m so it actually makes sense, as the wavelength is so "big" you can use the difference in time between peaks to measure "angle". You can also use Doppler to measure your speed going towards the sound source.
In general, to be able to walk the path with precision
- you need to know your heading
- you need to know your speed
with those 2 informations you can calculate where you are at any moment in time relative to starting position.
Now, the math gets bit complex, you need to use 2 sources ... they compensate each other and give you twice the resolution of only one + it allows you to have accurate measurement in "any direction" as with single sound source you would not be able to do any measurements going parallel to the source and you would have to sail like a sailboat (40 degrees one side, 40 degrees other side) in order to get where you wanted.